Sizing Turbos for Diesel Engines

Turbo Size: Understanding the Numbers behind compression-ignition

Diesel guys are number guys whether they know it or not. You’ll see the Big Three touting numbers in all of their ad campaigns: best in class towing, most torque, highest horsepower. In a day of little turbo economy cars, diesel numbers are almost always big. For many aftermarket enthusiasts, 500 rear-wheel horsepower and 1,000 lb-ft of torque is sort of the starting performance benchmark. Whether you’re good at math or not, numbers infiltrate virtually every aspect of the diesel market, so let’s have a look at them! We promise to try and keep it basic.

Engine Displacement

Almost all of the diesel engines we work with in the performance industry are large, but if there’s a displacement you can’t place (or you’re talking to an old hot rod guy) you can mix liters and cubic inches by taking the size in cubic centimeters (5.9L for instance = 5900cc) and dividing it by 16.38. This gives us 360.2 cubic inches. That means an 8.3L (8300cc) is 506 cid, and a 1.9L TDI is a tiny 116 cubic inches. It may be off by a decimal place or two, but the cubic inch to cubic centimeter can be helpful in everything from calculating airflow to sizing turbos, since most American hot rod math is non-metric.

Airflow

Another handy notation to have concerns airflow, which is simply cubic inches x rpm / 3456. That means a 360 cid engine (can you tell we like Cummins?) spinning at 3,000 rpm would consume about (360 x 3000 / 3456) 312 cfm of air when operating at 100 percent volumetric efficiency. However, volumetric efficiency is usually pretty far from 100 percent; more around 80 percent. So that means we now get an answer of (312 x .8) 249.6 (let’s just say 250) cfm of air. The great thing is, with these simple formulas you don’t even have to be that good at math, you just plug in a couple numbers and there’s your answer. If you’re wondering what airflow has to do with anything, we’re getting to that.

Turbos and Engines

So let’s say you have your Cummins spinning at 3,000rpm and you want to add some boost. Every atmosphere above outside air adds another bar to the pressure ratio, so if ambient is 14.7 psi (it varies by elevation) then 14.7 pounds of boost would be a 2:1 pressure ratio. That means 29.4 psi would be a 3:1 pressure ratio, and 73.5 psi would be a 6:1 pressure ratio. If we take our earlier theoretical 250 cfm figure, that means to make 14.7 pounds of boost you’d need a turbo that flows 500 cfm, 750 cfm for 3:1, and a whopping 1,500 cfm for 6:1. More than anything, this can be very helpful in sizing turbos for your desired power levels.

Turbos and Airflow

We get the question all the time: how do you size turbochargers? In reality, the answer is simple: turbos should be sized as small as possible for your desired horsepower. Luckily, airflow is one of those rare areas where the starts align, as roughly one pound per minute (lb/min) of air is equal to about 8 rear-wheel horsepower on a good running engine. That means a turbo that can flow 50 lb/min (we’re talking stock-ish here) would be good to about 400rwhp. For those looking to be right at 1,000rwhp, an S480 is a popular choice, which at 120 lb/min (120 x 8 = 960 rwhp) we can see why. Note that it’s also popular to make more power than the “formula,” but if you do it’s usually at the risk of overspeeding the turbo.

Fueling

Engine airflow math is fairly simple (with some exceptions, like intercooling), but fueling is a tough one to crack. Lots of things come into play, including injection pressure, timing, duration, nozzle size, and so on. One thing we can calculate fairly easily though, is the needs of a lift pump. Starting with a factory example, let’s take a truck that has a turbo that flows 50 lb/min of air and calculate the fuel needs to support that power level. Most factory engines run at around a 20:1 air/fuel ratio (or even higher) to keep smoke to a minimum, so we can see that at that airflow level, we’d need (50 / 20) 2.5 lb/min or .36 gal/min (diesel is around 6.93 pounds in weight) or (.36 x 60) 21.6 gph. Not very much. However, just richening the air/fuel ratio to 14:1 increases that need to 30.9 gph. On a big horsepower mechanical truck (let’s say 120 lb/min turbo, and 12:1 air/fuel ratio) we can see the need goes all the way up to 86 gallons per hour. Now, you may be wondering why there’s 100 and 150 gph pumps out there, if there’s only a need for 86 gph, even on a hot engine, and that answer has to do with pressure. As pressure goes up, flow decreases, as the pump has a harder and harder time pushing the fuel to the engine. A pump that free-flows 150 gph might only flow 120 at 20psi, 100 at 40 psi, and 80 at 60psi. Some pumps aren’t even made to run at those types of pressures, and might not get there at all. Also, the instant need for fuel once the pedal is mashed means that most people go with overkill so there’s no pressure drop when the engine suddenly demands fuel.

Nitrous Oxide

Nitrous oxide can be great fun on a diesel, or it can lead to a lot of headaches, depending on how it’s used. The most common misconception about nitrous is that a certain size jet equals a certain size “shot.” While this is true on gas engines (a 0.062 jet for instance, is a 150hp shot) on diesels it works totally different. Since diesels operate over a wide range of air/fuel ratios, more air doesn’t always mean more power. In a lightly fueled truck, an 0.080 jet might equal 50 hp; in a heavily fueled truck, the same 0.080 jet might be worth 200 horsepower. Also, since nitrous flow is based upon the area of a jet (3.14 x radius^2), a .100 jet is not twice the size of a .050 jet, it’s four times larger. Diesels are also capable of huge amounts of nitrous ingestion, even with the turbo. Two or three 0.125 jets on a diesel can be worth 500 hp or more.

Transmissions, Axles, and Tires

It’s hard to fit everything about transmissions, axles, and tires in one category, but it’s important to remember that they all are interrelated to each other. Change the gear ratio? The overall speed versus rpm of the vehicle changes. It’s the same with transmissions, and tire sizes. We’ll start with the easiest calculation, estimated speed versus rpm. Let’s say that our test vehicle is a ‘01 GMC with a five-speed transmission, 3.73 gears, and 32-inch tall tires. In fifth gear, the engine is overdriven via a .71 gear ratio, which means the effective final gear ratio is (3.73 x .71) a 2.65. So to figure out speed at say, 2,000 rpm, our equation is mph = (rpm x tire diameter) / (gear ratio x 336). The number 336 is just a constant, that gives you a correct result. So, our speed is (2,000 x 32) / (2.65 x 336) = 71.8 mph. This formula is probably the most useful in determining tire size changes, as we can see switching to 35’s would give us a big speed increase to (2,000 x 35) / (2.65 x 336) = 78.6 mph. Just like the other formulas, it’s not 100-percent accurate due to slippage, tire deflection, or other unknown variables, but usually it’s darn close.

 

In closing, breaking out the calculator can help you plan the next move for your truck, calculate power, or just help you day dream. As useful (and accurate) as most of these formulas are, there are still “freak” vehicles that can break the mold, and run quicker or make more power than physics should allow. So take all of these formulas with a grain of salt, and remember that math isn’t scary, it’s helpful!

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FREQUENTLY ASKED QUESTIONS

What turbo options are available for a diesel truck focused on speed and performance?

Turbo Options for High-Performance Diesel Trucks

When transforming your diesel truck into a speed and performance machine, turbo upgrades play a critical role. For enthusiasts who prioritize acceleration and power over utility, several turbo options are available, each with its unique advantages.

Variable Geometry Turbo (VGT) Upgrades

For those looking to maintain some versatility without compromising on performance, upgrading to a larger VGT is a popular choice. These turbos, like those in the 67mm family, offer improved airflow and can significantly boost your horsepower, pushing you past the 700hp mark. They are ideal for 5.9 or 6.7 Cummins engines and similar setups. VGTs provide a broad powerband and are relatively simple to install as drop-in replacements.

Fixed Vane Turbochargers

If you’re aiming for peak horsepower and are less concerned with low-end torque, a single fixed vane turbocharger might be the way to go. Although these turbos may lack the wide powerband of a variable geometry system, their free-flowing exhaust housings make them excellent for high-performance builds. Options are available that can handle up to 67mm and beyond, delivering impressive power with reduced exhaust gas temperatures (EGT).

Turbo Kits and Conversions

For serious truck enthusiasts, complete turbo kits that convert your existing setup into a high-performance beast are available. These kits often include different turbo sizes, ranging up to 72mm, catering specifically to brands like Cummins or Powerstroke engines. While these installations might demand more effort, the resultant power gain and performance enhancement make the investment worthwhile.

Performance Considerations

When choosing the right turbo for your truck, consider what aspects of performance are most critical to your driving needs. Whether you opt for a VGT for its ease and versatility or a fixed vane turbo for its robust power output, preparing your vehicle with larger injectors, a more powerful fuel injection system, and supportive engine modifications will help maximize your gains.

In summary, turbo options for those focused on speed and performance range from sizable VGT upgrades for balanced power and ease of use to high-output fixed vane turbos for pure horsepower. Each choice offers distinct advantages depending on your specific performance goals.

 

What happens if you install a turbo that is too large for your intended usage?

When considering turbo installation, size matters more than you might think. Opting for a turbo that is too large for your needs can introduce a range of challenges.

Slow Spool-Up Time

A large turbo requires significant exhaust energy to get moving. If your engine can’t provide that, you’ll experience a slow spool-up. This delay means sluggish performance, especially noticeable during city driving or cruising on highways.

Increased Throttle Demand

Because the turbo isn’t generating boost efficiently at lower RPMs, you’ll need to press the throttle harder to maintain speed. This leads to higher fuel consumption, as your engine works overtime without the expected boost in performance.

Elevated Exhaust Gas Temperatures (EGT)

The combination of more throttle input and low boost levels can result in increased exhaust gas temperatures. These higher temperatures can stress engine components, potentially leading to damage over time.

Power Surge

On the flip side, if conditions allow the turbo to spool up, you’ll experience a significant surge in power. This rush can be exhilarating and your EGTs will stabilize and even cool at maximum output, indicating the turbo is working efficiently at high power levels.

Poor Street Performance

Despite the benefits at peak performance, the downsides of everyday driving make a too-large turbo impractical for typical street use. It provides a power imbalance—great at high speeds, but inefficient and cumbersome at lower ones.

In summary, installing a too-large turbo can diminish driving comfort and engine efficiency, leaving you with high fuel costs and potential damage unless you’re constantly pushing the limits. Choose wisely to balance power and practicality.

 

What are the characteristics of a turbo suitable for a dual-purpose truck with some performance modifications?

Characteristics of a Turbo for a Dual-Purpose Truck with Performance Modifications

Driving a dual-purpose truck with performance modifications involves seeking a balance between fun and functionality. Owners of such trucks often have an appetite for speed, which translates into a few key modifications under the hood. These trucks commonly feature enhancements like performance tuning programs, cold air intakes, possibly upgraded intercoolers, larger-than-standard tires, and sometimes even reinforced transmissions due to past failures.

Power & Performance Balance

The turbocharger chosen for these trucks must be capable of delivering consistent power output while ensuring the vehicle remains practical for everyday use. This means it needs to handle increased power without elevating exhaust gas temperatures (EGT) excessively and provide efficient spool-up characteristics to prevent lag during acceleration.

Recommended Turbo Options

1. Drop-In Turbochargers:
   • Ideal for straightforward installation and balanced performance.
   • These turbos typically offer a good mix of power and utility without requiring extensive modifications or affecting the vehicle’s emissions systems.
2. Compound Turbo Kits:
   • Comprise two differently-sized turbochargers working together to cover a wide performance range.
   • While installation is more complex, these kits provide exceptional boost potential and improved engine torque. The setup helps to maintain quick spool-up thanks to the continued use of the stock turbo alongside a larger secondary turbo.
   • Particularly beneficial for those who utilize their trucks for towing, as they enhance power while reducing EGTs, effectively supporting over 600 horsepower on a stock fuel system.

Conclusion

Opting for either a drop-in turbo or a compound turbo kit depends on your priorities—whether you’re looking for easy installation or maximum towing capability. In both cases, the key is ensuring the turbo can handle increased power demands while staying true to the truck’s dual-purpose nature, balancing both performance and practicality.

 

What are the differences between variable geometry turbos (VGT) and fixed vane turbos?

Differences Between Variable Geometry Turbos (VGT) and Fixed Vane Turbos

When exploring turbocharger options, it’s crucial to understand the distinctions between variable geometry turbos (VGT) and fixed vane turbos. This knowledge can guide your decision-making in selecting the right performance enhancements for your vehicle.

Variable Geometry Turbos (VGT)

One of the standout features of VGTs is their adaptability. Modern engineering allows these turbos to adjust the position of their vanes, which are situated in the exhaust housing. These adjustable vanes direct exhaust gases optimally at varying engine speeds:

• At lower speeds, the vanes close, accelerating the turbo and minimizing turbo lag. This offers a quicker response for enhanced drivability.
• At higher speeds, the vanes open, allowing exhaust gases to flow freely. This maximizes power and reduces exhaust gas temperatures (EGT).

The key advantage of VGTs is their ability to offer the benefits of both smaller and larger turbos by adjusting within a broader operational range. This flexibility is why they’ve been a popular choice in the automotive industry for years.

Fixed Vane Turbos

In contrast, fixed vane turbos have a set geometry. This design does not allow for internal adjustments as engine speeds change. Consequently, these turbos are optimized for a specific performance range:

• Simplicity and reliabilityare often highlighted as strengths due to fewer moving parts.
• Consistent performancewithin their designated range, without the need for adaptive mechanisms.

However, their fixed nature means they may not perform optimally across a wide range of driving conditions like VGTs.

Key Differences

• Operational Range:VGTs have a broader range, whereas fixed vane turbos are confined to a predefined performance band.
• Complexity and Maintenance:VGTs are more complex, potentially requiring more maintenance due to their adjustable parts, while fixed vane turbos offer straightforward reliability.
• Performance Adaptability:VGTs can adjust to provide both quick acceleration and high power, whereas fixed vane turbos are tuned for consistent output in a narrower band.

Deciding between these two types depends on your vehicle’s needs and your performance goals. Whether you prioritize flexibility or simplicity, understanding these differences will lead to more informed decisions.

 

Why is there no one-size-fits-all solution for turbo sizing in diesel trucks?

Compound turbos can be a bit more difficult to size than single turbos, and can be geared towards response, all-around performance, or peak power. In general, the larger turbo should flow roughly twice what the small turbo will flow.

However, the right turbo setup isn’t a one-size-fits-all solution. It largely depends on how you plan to use your truck. Are you looking for quick response times, or is your priority achieving peak power for towing heavy loads? Perhaps you’re seeking balanced performance for daily driving and occasional off-road adventures. Each scenario demands a different approach to turbo sizing.

To simplify the decision-making process, consider breaking down your usage into categories:

1. Quick Response: Ideal for those who need immediate power delivery.
2. All-Around Performance: Perfect for balanced driving needs.
3. Peak Power: Suited for maximum output and heavy-duty tasks.

By identifying which category best fits your requirements, you can better determine the appropriate turbo size. If you’re still uncertain, consulting with experienced professionals can provide tailored recommendations to ensure your setup meets your specific needs.

 

What turbo considerations are necessary for a race truck aiming for high horsepower?

Turbos and Airflow

We get the question all the time: how do you size turbochargers? In reality, the answer is simple: turbos should be sized as small as possible for your desired horsepower. Luckily, airflow is one of those rare areas where the stars align, as roughly one pound per minute (lb/min) of air is equal to about 8 rear-wheel horsepower on a good running engine. That means a turbo that can flow 50 lb/min (we’re talking stock-ish here) would be good to about 400rwhp. For those looking to be right at 1,000rwhp, an S480 is a popular choice, which at 120 lb/min (120 x 8 = 960 rwhp) we can see why. Note that it’s also popular to make more power than the “formula,” but if you do, it’s usually at the risk of overspeeding the turbo.

For those venturing into the race truck realm, where horsepower exceeds 850, choosing the right turbo setup becomes even more critical. At these elevated levels, a single S400-based 80mm turbo can be a gateway to 1,000 horsepower, while a compound setup with a larger 106mm turbo can push into the 2,000-horsepower range. This choice depends heavily on whether you prioritize peak power or a balanced performance across various conditions.

Compound Turbo Considerations

Compound turbos can be a bit more difficult to size than single turbos, and can be geared towards response, all-around performance, or peak power. In general, the larger turbo should flow roughly twice what the small turbo will flow. This setup is perfect for those seeking a balance between quick spool-up and maximum power output.

However, achieving such high power doesn’t stop at the turbos. You’ll need a fortified engine with stronger pistons and rods, a performance camshaft, and a robust valvetrain. A massive fuel system is essential to support these modifications, and a built transmission is critical to handle the immense stress.

Safety and Practical Considerations

Don’t forget the racing-specific equipment like a roll cage and drag slicks, which are essential for safety and performance on the track. While these setups deliver breathtaking power, their street usability can be limited due to slow spool-up times, so it’s crucial to weigh your priorities.

In summary, understanding airflow and turbo sizing is just the beginning. Comprehensive vehicle modifications and strategic planning are key to unlocking the full potential of your race truck.

 

How do engine modifications affect turbo performance?

Turbos and Engines

So let’s say you have your Cummins spinning at 3,000rpm and you want to add some boost. Every atmosphere above outside air adds another bar to the pressure ratio, so if ambient is 14.7 psi (it varies by elevation) then 14.7 pounds of boost would be a 2:1 pressure ratio. That means 29.4 psi would be a 3:1 pressure ratio, and 73.5 psi would be a 6:1 pressure ratio. If we take our earlier theoretical 250 cfm figure, that means to make 14.7 pounds of boost you’d need a turbo that flows 500 cfm, 750 cfm for 3:1, and a whopping 1,500 cfm for 6:1. More than anything, this can be very helpful in sizing turbos for your desired power levels.

Figuring out exactly how much a turbo will flow requires a bit of help from the manufacturer. Companies like Garrett and BorgWarner provide access to compressor maps, which show the maximum pressure ratio, flow, and compressor speed.

Engine Modifications and Turbo Performance

While turbo sizing is crucial, it’s important to remember that other engine modifications can significantly impact turbo performance. For optimal engine performance, the air and fuel your engine consumes must be balanced. If you decide to increase fueling with larger injectors or a dual injection pump, you must also increase airflow. Failing to do so could lead to issues like high exhaust gas temperatures (EGT), which compromise engine efficiency.

Imagine a turbo that’s perfectly matched with a stock fuel system. With a set of larger injectors and a high-performance tune, that same turbo might be too small, unable to provide the necessary airflow. When upgrading, consider installing a larger turbo first and keeping the stock fuel system. This approach minimizes risks and ensures smoother transitions between modifications.

Turbos and Airflow

We get the question all the time: how do you size turbochargers? In reality, the answer is simple: turbos should be sized as small as possible for your desired horsepower. Luckily, airflow is one of those rare areas where the stars align, as roughly one pound per minute (lb/min) of air is equal to about 8 rear-wheel horsepower on a good running engine. That means a turbo that can flow 50 lb/min (we’re talking stock-ish here) would be good to about 400rwhp. For those looking to be right at 1,000rwhp, an S480 is a popular choice, which at 120 lb/min (120 x 8 = 960 rwhp) we can see why. Note that it’s also popular to make more power than the “formula,” but if you do it’s usually at the risk of overspeeding the turbo.

Compound turbos can be a bit more difficult to size than single turbos, and can be geared towards response, all-around performance, or peak power. In general, the larger turbo should flow roughly twice what the small turbo will flow.

By considering both turbo sizing and the effects of engine modifications, you can fine-tune your setup to achieve the ideal balance of power and reliability.

 

How do exhaust gas temperatures (EGTs) differ between diesel and gasoline engines, and how does that affect turbo choice?

Understanding EGTs in Diesel vs. Gasoline Engines and Their Impact on Turbo Selection

When comparing diesel and gasoline engines, one significant difference lies in their exhaust gas temperatures (EGTs). Gasoline engines typically operate at higher EGTs than diesel engines. This is primarily due to the difference in combustion processes. Gasoline engines produce more heat because they run at higher RPMs and with a stoichiometric air-fuel mixture, which leads to those elevated temperatures.

How EGTs Influence Turbo Choice

1. Material Selection:
   • Turbos for gasoline engines often need to withstand higher temperatures, so manufacturers may opt for materials like Inconel, a high-temperature-resistant alloy, for key components such as turbine housings.
2. Durability Requirements:
   • While diesel turbos may not face the same extreme temperatures, they are typically designed for longevity and robustness due to their allocation for engines that frequently aim for extended warranties, often reaching 500,000 to a million miles.
3. Design Considerations:
   • Designing around the specific EGTs for each engine type involves ensuring the turbo can handle the thermal cycles encountered during operation without degradation in performance or reliability.

Thus, understanding the EGT characteristics of an engine is crucial in selecting or designing a turbocharger that will perform efficiently and endure the stresses over its expected lifespan.

 

How do weight and efficiency considerations impact the choice of a turbocharger for high-performance applications?

Turbocharger Weight and Efficiency Considerations

When selecting a turbocharger for high-performance applications, weight and efficiency are key factors that can greatly influence performance outcomes.

Weight Matters

Turbochargers are inherently heavy components, which can affect the overall weight distribution and handling of a vehicle. For instance, consider two types of 70mm turbochargers. A standard turbo for a truck might weigh around 56 pounds, whereas an aftermarket version could only be 25 pounds. The lighter option allows for quicker vehicle response due to reduced inertia and improved balance. This difference is crucial in high-performance vehicles, where every ounce counts.

To optimize performance, professionals often strive to shave off weight from multiple areas. Removing as little as 1 ounce from 80 different components can be equivalent to gaining an extra horsepower. This cumulative weight reduction strategy is integral in achieving precise performance metrics.

Efficiency: The Power Within

Efficiency is another critical element. Turbochargers need to operate within their optimal efficiency range on the compressor map. A turbo that’s not running in this “sweet spot” may result in higher discharge temperatures and less power output. For example, a truck turbo may require an additional 6 horsepower just to operate compared to a more efficient aftermarket turbocharger. This extra energy expenditure translates to increased operational costs and diminished performance.

In high-performance scenarios, choosing a turbocharger that matches the vehicle’s power requirements and operating conditions can be a balancing act. While it might be more expensive initially, a well-chosen turbo can maximize power output and ensure longevity, making the investment worthwhile.

The Right Compromise

The decision to select the right turbo involves weighing these factors against budget constraints, especially in competitive racing scenarios. While some compromises are inevitable, prioritizing both weight reduction and efficiency allows for better performance and a more manageable cost in the long run.

By strategically evaluating turbocharger options under these considerations, enthusiasts and engineers can enhance vehicle performance without overspending.

 

What are the benefits and drawbacks of using a larger intercooler in relation to turbo performance?

Benefits and Drawbacks of Using a Larger Intercooler in Relation to Turbo Performance

When it comes to turbocharged engines, the choice of intercooler size can significantly impact performance. Let’s explore both the benefits and drawbacks of opting for a larger intercooler.

Benefits of a Larger Intercooler

1. Increased Air Density:
   • A larger intercooler enhances air cooling before it enters the engine. This results in denser air, allowing for more oxygen in the combustion process, which can improve overall power output.
2. Reduced Intake Temperatures:
   • By efficiently lowering intake temperatures, a larger intercooler helps prevent engine knock and detonation, ensuring more stable and reliable engine performance under high boost conditions.
3. Enhanced Engine Efficiency:
   • With cooler intake air, the engine can achieve higher thermal efficiency. This means that for the same amount of fuel, more power can be extracted, maximizing the engine’s potential.

Drawbacks of a Larger Intercooler

1. Increased Weight:
   • Larger intercoolers tend to be heavier, which can be a concern in performance applications where every ounce counts. This added weight can offset some of the gains in power.
2. Pressure Drop:
   • With increased size, there is a potential for greater pressure drop across the intercooler. This can lead to slightly reduced boost levels reaching the engine unless the turbocharger compensates by working harder.
3. Space and Fitment Issues:
   • Finding space for a larger intercooler can be challenging in compact engine bays. Modifications may be necessary, which can increase costs and complexity.
4. Cost Considerations:
   • Larger intercoolers are typically more expensive. For budget-conscious builders, this can be a significant drawback, especially when balancing against other performance parts.

Conclusion

Selecting the right intercooler size involves weighing these pros and cons alongside your specific performance goals and budget constraints. While a larger intercooler can unlock more power and efficiency, it’s essential to consider its impact on weight, pressure, and overall vehicle setup.

 

How have turbocharger options and technologies evolved since the publication of older reference books?

Evolution of Turbocharger Options and Technologies

Turbocharger technology has come a long way since the mid-’90s, when older reference books were first published. Here’s a look at how advances have reshaped the landscape:

• Diverse Variety: Over the past two decades, the market has seen a significant increase in turbocharger options. This expansion encompasses both diesel and gasoline engines, offering a more tailored approach for different vehicle types and performance needs.
• Improved Efficiency: Modern turbos are engineered for better fuel efficiency and power output. Engineers have honed designs to minimize lag and maximize response time, providing smoother performance.
• Advanced Materials and Designs: Innovations in materials, such as the use of lightweight alloys and ceramic components, have contributed to greater durability and higher temperature tolerance. Designs have also become more compact, aiding in easier installation and integration with contemporary engine systems.
• Variable Geometry Technology: One of the most significant advancements is the introduction of Variable Geometry Turbochargers (VGTs). These smart systems adjust the flow of exhaust gases through the turbocharger to optimize performance across a wider range of speeds and driving conditions.
• Electronic Control Systems: The integration of electronic controls has allowed for more precise management of turbocharger operation. This leads to better fuel management and reduces emissions, aligning with modern environmental standards.
• Hybrid and Electric Assist: Cutting-edge hybrid turbo systems incorporate electric motors to further reduce lag and provide instant boost. These systems are becoming more commonly integrated into high-performance and hybrid vehicles, pointing to a future of even more sophisticated turbo technology.

In sum, turbocharger technology has significantly advanced, offering a plethora of options that ensure enhanced performance, efficiency, and adaptability to modern engine demands. The landscape today is vastly different from what was captured in older publications, reflecting the pace of innovation and consumer demand.

 

What is a quick-and-dirty method for selecting a used OEM turbo?

How to Quickly Choose a Used OEM Turbo

When you’re looking to select a used OEM turbo and time is of the essence, there’s a straightforward method you can follow.

1. Determine Your Engine’s Displacement: Start by knowing the size of your engine in terms of displacement. This will serve as the basis for your search.
2. Identify Desired Power Output: Establish the power level you wish to achieve. Having a clear target will guide your selection process.
3. Find a Match: The key is to look for vehicles that match both your engine’s displacement and your desired power output. Seek out cars with engines similar in size and power to what you have or want.
4. Sourcing the Turbo: Once you have a list of potential donor cars, find a turbo from one of these matching vehicles. This ensures compatibility and performance that aligns with your criteria.

By following these steps, you can effectively select a used OEM turbo that meets your needs with minimal fuss.

 

How can online calculators or spreadsheets assist in turbocharger selection?

Harnessing Online Calculators and Spreadsheets for Turbocharger Selection

Choosing the right turbocharger can significantly enhance your vehicle’s performance, but it requires careful consideration of various factors. Online calculators and spreadsheets are invaluable tools that can streamline this process and ensure accurate selection. Here’s how they assist:

1. Precision and Accuracy

Online calculators, like those from reputable automotive websites, provide precise calculations for critical parameters, including air flow, boost pressure, and engine displacement. This precision helps eliminate guesswork, ensuring that you select a turbocharger tailored to your engine specifications.

2. Ease of Comparison

It’s easier to compare different turbocharger options using spreadsheets. By inputting data on power output, efficiency, and compatibility, you can visually contrast various models. This comparison helps in understanding the benefits and drawbacks of each option, making it easier to pick the one that suits your needs.

3. Customization and Flexibility

Spreadsheets offer customization, allowing you to tweak formulas according to your specific engine setup. Want to simulate the impact of different boost levels or ambient conditions? Spreadsheets let you manipulate variables to see potential outcomes, offering a dynamic approach to your selection process.

4. Learning and Exploration

Both calculators and spreadsheets offer learning opportunities. As you play around with different inputs and see the results, you gain a deeper understanding of how various factors influence turbocharger performance. This exploration can prepare you for making informed decisions.

5. Time Efficiency

Using these tools saves time. Calculators automate complex equations, while spreadsheets organize information efficiently. This means you can focus more on analysis and decision-making rather than getting bogged down in manual calculations.

In summary, leveraging online calculators and spreadsheets takes the stress out of turbocharger selection by offering accuracy, efficiency, and insight. They are instrumental in aligning your vehicle’s performance goals with the technical capabilities of available turbochargers.

 

What are the potential issues with using a diesel turbo on a gasoline engine?

Potential Issues with Using a Diesel Turbo on a Gasoline Engine

When considering the use of a diesel turbocharger with a gasoline engine, several potential issues can arise due to differences in engineering and operating environments. Here’s a breakdown of the main concerns:

1. Exhaust Gas Temperatures (EGTs)

• Diesel vs. Gasoline EGTs: Diesel engines typically operate at lower exhaust gas temperatures compared to gasoline engines. While diesel turbos are designed to handle EGTs of around 1200-1300°F, gasoline engines can push this range to the upper limits, with testing temperatures reaching up to 1600-1700°F.
• Impact on Components: Higher EGTs from gasoline engines can lead to severe stress on the turbine housing, potentially causing cracks and, though less likely, turbine blade failures. The use of materials such as Inconel in turbine casting helps mitigate this, but it’s not a guaranteed safeguard.

2. Turbine Housing and Blade Material

• Material Suitability: Turbine housings and blades in diesel turbochargers might not be made to withstand the prolonged high heat exposure that gasoline engines can produce. This can result in mechanical failures if the material cannot endure the elevated temperatures.

3. Shaft Seal Failures

• Seal Integrity: Diesel turbos using conventional shaft seals might be more prone to failure in the more intense thermal environment of a gasoline engine. This can lead to oil leakage and reduced turbo efficiency.

4. Performance Mismatch

• Design Disparity: Diesel turbos are engineered for different airflow and pressure demands. This means they might not optimize engine performance or fuel efficiency when used in a gasoline engine setting.

Conclusion

Using a diesel turbocharger in a gasoline engine poses several risks primarily due to differences in operational temperatures and materials. Any modifications should be carefully evaluated and engineered to ensure the longevity and performance of the turbocharger in a gasoline application.

 

What are some recommended resources or books for learning about turbochargers?

Recommended Resources for Learning About Turbochargers

When diving into the world of turbochargers, selecting the right educational resources is crucial. Whether you’re a beginner or looking to refine your expertise, the journey begins with understanding both the fundamental principles and the evolving technologies.

Classic Literature

One classic resource that lays the groundwork for turbocharger knowledge is “Maximum Boost” by Corky Bell. While some of its content on engine management systems may be outdated, the core principles of turbocharger design and operation remain valid. This book provides a solid theoretical foundation that can be augmented by modern tools and resources.

Educational Techniques

1. Online Calculators and Simulations: After grasping the basic concepts, applying mathematical models with online calculators can help you visualize and experiment with different turbo setups. These tools allow you to play around with variables such as boost levels and airflow, providing hands-on experience without physical setup.
2. Spreadsheets: Creating your own spreadsheets to track various parameters can assist in understanding the relationship between cost, availability, and performance. This method encourages a deep dive into data analysis and decision-making for custom builds.

Digital Maps and Databases

A crucial aspect of turbocharger technology is interpreting compressor maps. Many manufacturers provide these maps online, enabling you to compare different models and designs. These resources are invaluable for making informed choices about which turbochargers might best suit your needs.

Updated Perspectives

While “Maximum Boost” offers a historical perspective, it’s important to complement it with current information. Seeking out forums, online communities, and recent publications can provide insights into the latest advancements and trends in turbocharging, ensuring your knowledge is up to date with today’s standards.

In summary, to effectively learn about turbochargers, start with foundational literature, then leverage modern tools and resources to bridge the gap between theory and practice. By doing so, you’ll be well-equipped to navigate the complexities of turbocharger systems.

 

What are the potential advantages of using a Holset turbocharger on a four-cylinder engine?

Advantages of Using a Holset Turbocharger on a Four-Cylinder Engine

When considering turbocharger options for a four-cylinder engine, the Holset turbocharger emerges as a compelling choice due to several practical benefits.

1. Cost-Effectiveness:
   One of the major advantages of the Holset turbocharger is its affordability. Compared to other turbo options, Holsetturbos are budget-friendly while still delivering robust performance. This makes them accessible to enthusiasts and tuners who seek impressive results without breaking the bank.
2. Ease of Maintenance and Rebuild:
   Holset turbochargers are not only inexpensive but also surprisingly simple to maintain and rebuild. Even individuals with basic mechanical skills and a few essential tools can restore these turbos to like-new condition. This ease of maintenance means less downtime and more time enjoying enhanced engine performance.
3. Proven Performance and Reliability:
   With a track record spanning decades, Holset turbochargers have established a reputation for reliability and effectiveness. Although they may not represent the pinnacle of turbocharging efficiency, their dependable performance is beyond question. These turbos have been extensively tested and trusted in various automotive applications, ensuring that your four-cylinder engine benefits from their durability.
4. Enhanced Power and Spool Time:
   Holset turbochargers can significantly increase the power output of a four-cylinder engine. By incorporating features that improve spool time, they enable quicker power delivery, making your vehicle’s acceleration feel more dynamic. This added power transforms the engine, giving it the ability to operate with the strength of much larger engines, akin to a freight train.

In summary, opting for a Holset turbocharger on a four-cylinder engine provides a blend of affordability, ease of maintenance, and reliable power enhancements. This makes it a popular choice for automotive enthusiasts looking to elevate their ride’s performance without overextending their budget.

 

What is the significance of matching turbo size with engine displacement and power goals?

Choosing the appropriate turbocharger size ensures that your vehicle can handle a variety of tasks smoothly, whether you’re on the highway or tackling heavy loads. It enhances overall driveability and mechanical efficiency, making it an ideal choice for most diesel pickup owners. In short, identifying the Goldilocks zone in turbo sizing transforms your driving experience, maximizing both performance and fuel economy without sacrifices.

Understanding the Importance of Turbo Sizing

When seeking the perfect turbo for your vehicle, consider these crucial factors:

• Engine Displacement: Matching the turbo size to your engine’s displacement ensures optimal performance. This alignment allows the engine to breathe efficiently, providing the power boost you desire.
• Power Goals: Define your horsepower targets. For instance, if you’re aiming for a 250+ hp range, the right turbo can make all the difference in achieving those numbers without compromising control or efficiency.
• Spool Characteristics: Consider how quickly you want the turbo to spool. A well-sized turbo will match your driving style and needs, ensuring quick response and seamless integration with your powerband.

Practical Examples and Considerations

Is your goal to reach 300-350hp with a 2L 4-cylinder engine? Turbos typically used in high-performance models like the Mitsubishi Evo or Subaru STi might be your best bet. These examples illustrate how the right turbo can meet specific performance needs while maintaining balance and control.

Moreover, selecting an appropriately sized turbo can transform your vehicle’s handling dynamics. For vehicles like the AW11 MR2, maintaining control under power is crucial. Finding the right turbo ensures your vehicle remains manageable, enhancing both satisfaction and safety on the road.

In conclusion, understanding the significance of turbo sizing goes beyond just numbers. It’s about creating a harmonious driving experience where power, efficiency, and control intersect perfectly.

 

How does turbo sizing affect driver satisfaction?

Properly sizing a turbo ensures it aligns well with the engine’s powerband and spools efficiently, leading to a satisfying driving experience. It translates to smoother power delivery and a more enjoyable ride, regardless of the exact horsepower achieved.

 

How do power goals relate to vehicle control and performance?

Power goals are directly tied to how manageable a vehicle is under power. For instance, an AW11 MR2 becomes challenging to control at higher power levels, so setting a goal of around 250+ horsepower balances performance with handling.

 

What are some examples of turbochargers suitable for a particular engine and power goal?

For a 2L 4-cylinder engine aiming for 300-350 horsepower, a turbo from vehicles like the Mitsubishi Evo or Subaru STi can be ideal as they historically use similar setups.

 

What factors should be considered when selecting a used OEM turbo?

When selecting a used OEM turbo, it’s crucial to consider your engine’s displacement, your power goals, and how quickly you want the turbo to spool. These specifics help in choosing a turbo that matches your vehicle’s performance needs.

 

What are some common online tools or calculators available for turbo selection?

Turbo Selection Calculators

If you want to take some of the guesswork and napkin math out of sizing your turbo, there’s good news: there are a number of online calculators and resources designed to help you zero in on the right choice for your setup. These tools typically let you input details like engine displacement, target boost, and desired horsepower, then spit out recommended turbo specs or even specific models.

A few handy options in the toolbox include:

• Garrett’s Boost Adviser– Plug in your info and see a short list of Garrett turbos that fit your parameters.
• BorgWarner MatchBot– This online tool steps you through flow, pressure ratios, and helps you visualize compressor maps.
• Forced Induction and Squirrel Performance Calculators– There are general calculators on enthusiast sites as well as dedicated turbo tech forums that walk you through the process.
• General Automotive Calculators– Some sites let you compare many brands and even factor in altitude or intercooler efficiency.

While these calculators don’t replace a solid understanding of the fundamentals, they definitely make the math a little less daunting. They’re a great first stop while planning out your build or bouncing between different combinations.

 

What are some budget-friendly turbo options for making high power?

Budget-Friendly Turbo Options for High Power

So, what if you want to go fast without draining your wallet? Good news: there are plenty of affordable turbo options that have been proven to perform, even for those piecing together a setup on a shoestring budget. One popular route is utilizing diesel turbos. Sure, they might be on the hefty side, but they’re known for being durable and easy to rebuild—anyone handy with a torch and some basic tools can have them spinning like new in no time. These turbos have a track record stretching back years, being swapped onto everything from four-cylinder builds to V8s, and more often than not, they just plain work.

Are these the most cutting-edge, highly efficient turbos you can buy? Not really—but what they lack in top-end efficiency, they make up for in reliability, availability, and a proven ability to deliver strong, usable power. If you’re looking for something even more wallet-friendly, the world of aftermarket turbos from companies like VS Racinghas exploded recently. They offer budget turbos that are becoming increasingly robust, with countless enthusiasts putting them through their paces on high-horsepower street builds, often with impressive success.

The takeaway? You don’t have to spend a small fortune to get into boost. Whether you go with a time-tested diesel turbo or a budget-friendly aftermarket unit, there are options out there to help you make big power without emptying your pockets.

 

How does turbo weight and efficiency impact vehicle performance, especially in racing scenarios?

Turbo Weight and Efficiency

When it comes to racing, the size and weight of your turbocharger can definitely tip the scales on performance—sometimes quite literally. On slower cars, like those running in the 11-second quarter-mile range, using a heavier or oversized turbo doesn’t do too much damage; as long as you see a power gain that outweighs the added heft, your time slip should still improve. For example, bolting on an intercooler and piping package that adds 30 pounds only needs to net you around 3 additional horsepower to actually make the car quicker down the track.

As you step up the ladder to faster cars, the equation changes fast. An 8.90-second car will need to claw back nearly 8 horsepower just to offset the effects of a heavier intercooler or turbo. The same goes for turbos specifically: larger truck-style turbos can sometimes weigh in at double the weight of their aftermarket counterparts (think 56 pounds versus 25). That’s not just dead weight—you might need an extra 6 horsepower just to turn that heavier turbine, not to mention the potential for increased discharge temps if the turbo isn’t operating in the sweet spot of its efficiency map.

This means that, especially in high-stakes racing builds, it often pays to choose the lightest, most efficient turbo that can support your horsepower goals. Of course, factors like physical packaging in the engine bay and overall durability are part of the puzzle too. But the lesson here is that every ounce matters: savvy builders will often look for dozens of small ways to trim weight, knowing that each little change adds up. The closer you can right-size your turbos, intercoolers, and related hardware, the faster you’ll be for any given amount of horsepower.

 

What are some cost-effective options for turbocharging small displacement engines?

Turbo Options for Small Displacement Engines

When it comes to turbocharging smaller displacement engines, staying within the right size range is key for both performance and budget. Turbos originally designed for engines around 2.0 to 2.5 liters are usually a great starting point—think factory units from vehicles in this sweet spot. If you’re hunting for more power, you might consider turbos sourced from somewhat larger engines (still within reason), as they can offer additional airflow potential without tipping the scales toward laggy, oversized territory.

One of the main perks of going this route is affordability. These turbos are often plentiful in the used market, and surprisingly friendly to those who like to wrench—it doesn’t take much more than basic tools and some patience to bring a tired unit back to life. In fact, with a little backyard ingenuity—a good set of snap ring pliers and a can-do attitude—most folks can have a used turbo spinning like new without breaking the bank.

While not every turbo from this category will be the absolute last word in efficiency, you’ll find many proven, reliable options that can wake up a small four-cylinder and make it feel like it’s been sipping rocket fuel. This approach balances both practicality and price, making it a favorite among enthusiasts experimenting with custom builds or chasing better performance on a budget.

 

What factors should be considered when selecting a turbocharger for a 1.8-2.0 liter engine?

Selecting a Turbocharger for 1.8–2.0L Engines

Choosing the right turbo for an engine in the 1.8 to 2.0 liter range isn’t about guesswork—it’s about matching the turbo’s characteristics to your power goals and how you want the car to drive.

Consider Your Base Engine Size

Start by focusing on turbos that originate from engines of similar displacement. Turbos from 2.0 to 2.5 liter engines are usually a solid fit, delivering respectable spool-up times and enough airflow for moderate power increases without burdening your pocketbook. If you’re after more horsepower (say, north of 250), you might consider turbos from slightly larger engines, provided you’re willing to accept a bit more lag for the extra top-end flow.

Think About the Application

How you’ll use the car plays a big role:

• Street performance: Quick boost response is king, so select a turbo that reaches full boost soon enough for street driving. OEMs often fit compact, responsive turbos for this reason.
• Track or drag: If you don’t mind waiting a bit for the turbo to spool—perhaps because you have a high-stall torque converter—you might size up for bigger top-end power.

Ideally, your chosen turbo will provide strong midrange pull and continue to deliver nearly up to redline. Avoid one so small that you overshoot the powerband with every gear shift.

Do the Math

Now’s the time to dust off that spreadsheet or turbo calculator. Tools online let you plug in your engine size, anticipated rpm range, and desired boost to estimate airflow needs (cfm or lbs/min). From there, cross-reference those numbers with turbo compressor maps produced by folks like Garrett or BorgWarner. This helps ensure your turbo is in its happy place—not too big, not too small—throughout your actual operating range.

Learn from the Classics (But Stay Current)

Books like Maximum Boost are great for turbo theory, but remember: turbo technology marches on. Always cross-check with the latest compressor maps and product info to leverage advances from the last couple of decades.

Fine-Tuning

Finally, your ideal setup is one where the turbo doesn’t choke off power prematurely (running out of breath before redline), nor does it spool so slow that you’re waiting an eternity for boost. It’s a balancing act. Aim for a turbo just large enough that it keeps delivering strong airflow right up until redline, but without lag that saps street fun.

If you plan further upgrades down the road, consider future-proofing your build by choosing a turbo that allows for a little headroom—so you’re not back at square one should you get bitten by the horsepower bug.

Airflow

Another handy notation to have concerns airflow, which is simply cubic inches x rpm / 3456. That means a 360 cid engine (can you tell we like Cummins?) spinning at 3,000 rpm would consume about (360 x 3000 / 3456) 312 cfm of air when operating at 100 percent volumetric efficiency. However, volumetric efficiency is usually pretty far from 100 percent; more around 80 percent. So that means we now get an answer of (312 x .8) 249.6 (let’s just say 250) cfm of air. The great thing is, with these simple formulas you don’t even have to be that good at math, you just plug in a couple numbers and there’s your answer. If you’re wondering what airflow has to do with anything, we’re getting to that.Subscribe Our Weekly NewsletterAn engine’s peak rpm has a big effect on airflow. A 5,000-rpm race engine will be gulping in a lot more air per second or minute than a 2,500-3,000 rpm stocker.

 

How do the cost and reliability of Chinese turbos compare to other options?

Turbo Cost and Reliability: Chinese Options

Naturally, everyone wants the best bang for their buck, so it’s no surprise that plenty of folks gravitate toward Chinese turbos. Historically, these have been popular simply because they’re widely available and incredibly wallet-friendly compared to some of the big-name options.

But here’s where it gets interesting—Chinese turbos have made big strides in both reliability and performance. Brands like VS Racing have developed a bit of a cult following, especially among budget-minded LS enthusiasts pushing serious horsepower with impressive results and very few issues. While you might not get the flashiest logo, these turbos now offer a solid blend of affordability and durability, making them a viable contender when you’re weighing up cost versus reliability.

If you’re looking to stretch your dollar and still lay down some big power, these new-generation budget turbos definitely deserve a look.

 

What is the recommended approach to learning about turbocharger theory and selection for beginners?

Getting Started: Learning Turbocharger Theory for Beginners

If you’re new to the world of turbocharging and want to wrap your head around how these magical snail shells work, there’s no better place to start than with a little light reading. Corky Bell’s classic, “Maximum Boost,” still stands as a solid foundation for understanding the basics of boost, pressure ratios, compressor maps, and everything else that makes turbos tick. While the book has been around for a while and you might spot some outdated details, its fundamental theory remains relevant—and is the backbone of much of modern turbo wisdom.

Once you’ve brushed up on the basics, it’s time to get your hands (digitally) dirty. Hop online and check out popular turbo calculators and compressor maps—you’ll find a treasure trove of resources that help take the guesswork out of matching the right turbo to your engine. Most major turbo manufacturers provide access to their compressor maps, and sites with interactive calculators let you punch in your numbers to see what makes sense for your build.

If you’re mathematically inclined, consider building your own airflow or turbo sizing spreadsheet. This is a great way to visualize how your choices play out across different operating conditions, and you can tweak variables to see how things stack up.

No matter the path you choose, just remember: learning the theory first will save you time (and possibly expensive mistakes) down the road, and there’s no shortage of resources available to help you get started.

 

What are the advantages and disadvantages of using stock turbos from 2.5-liter or larger engines?

Stock Turbos: Pros and Cons

You might be eyeing turbos from 2.5-liter engines (or even slightly larger powerplants) and wondering if they’re a good fit for your project. As it turns out, factory turbos from these midsize engines can be a solid option, especially if you’re aiming for moderate horsepower goals without breaking the bank. Here’s why:

Advantages

• Affordability:Stock turbos—especially those sourced from diesel engines—are surprisingly easy on the wallet. They’re widely available and, thanks to the sheer number in circulation, can be picked up for a bargain.
• Durability:Designed for long life and daily abuse, these OEM turbos are often robust and built to handle significant use.
• Simplicity of Rebuild:Many of these units can be rebuilt at home with basic tools (and perhaps a little bit of bravery with snap ring pliers and a torch thrown in for good measure). Parts are budget-friendly, so giving a tired turbo a new lease on life doesn’t require a deep wallet or a PhD in engineering.
• Proven Track Record:There’s a mountain of evidence out there—particularly from communities running Holset, Garrett, or BorgWarner units—that these stock turbos perform well and reliably when swapped onto 4-cylinder engines looking for a boost in performance.

Disadvantages

• Weight:Diesel turbos, in particular, can be on the heavier side, which could be a consideration if every ounce matters in your build.
• Efficiency:While stock turbos are often durable and inexpensive, they’re not always the last word in turbo efficiency. You might not wring every drop of potential power or spool response that a high-end aftermarket turbo could deliver.
• Fitment and Sizing:Going with a larger stock turbo (say, from a 3-liter engine) can net you more power, but may introduce lag if not matched carefully to your engine’s displacement and operating range.

In summary, stock turbos from 2.5- to 3-liter diesels (or similar gas engines) are a favorite for budget builds, delivering reliable grunt and very reasonable pricing. Just remember, it’s always a game of tradeoffs: you get reliability and economy, but possibly at the expense of some efficiency or outright power.

 

How have advancements in turbocharger technology changed the options available since the late 1990s?

Turbo Technology: The Evolution Since the ’90s

When it comes to picking the right turbo, it’s important to remember just how much the landscape has changed over the past couple of decades. Back in 1997, the options were a little more limited and the technology was, let’s just say, simpler. Fast forward twenty-plus years, and we’ve seen a turbo explosion—both in terms of variety and what these units are capable of.

Today’s turbos benefit from massive advancements like variable geometry turbines (VGTs), improved bearings (think ball vs. Journal), and significantly more efficient compressor wheel designs. Brands like BorgWarner and Garrett have pushed the envelope with units that spool faster, deliver more air, and handle higher pressures—all while being friendlier to everyday driving and big horsepower builds alike.

All these improvements mean the modern enthusiast has access to a much broader range of turbos, with the ability to fine-tune for a specific application, whether it’s low-end grunt, high-rpm power, or the holy grail: both. If you’re referencing old turbo maps or sizing charts, remember they might not capture the full capabilities (or even the existence) of some of today’s best options.

Technology hasn’t just marched forward—it’s sprinted, bringing new choices for both diesel and gas engines that would’ve seemed like science fiction to the ’90s hot-rodders.

 

How reliable and easy to rebuild are diesel turbos for performance applications?

Reliability and Rebuilding of Diesel Turbos

One of the perks of running diesel turbos in your build is their impressive blend of durability and simplicity. These turbos are usually built to handle the kind of stress and abuse that would send most gas units packing, making them a popular choice for budget-minded performance enthusiasts. And when it comes time for a refresh, the good news is you don’t need a secret apprentice or a NASA facility. A basic set of hand tools (think snap ring pliers and a propane torch) and a rebuild kit are often all it takes to get one spinning smooth again.

In terms of reliability, tried-and-true models like the Holset HX35, especially when paired with things like a BEPturbine housing for quicker spool up, have been favorite upgrades in the performance community for years. Sure, they’re not always the last word in efficiency, but they more than make up for it by being robust, readily available, and easy to revive on a weekend in your garage. This is part of the reason you’ll see so many four-cylinder builds waking up with a diesel turbo under the hood—they’re a surefire way to get big power without breaking the bank or the wrench.

 

Should readers rely on older literature for current turbocharger technology, or seek out newer resources?

Should You Trust Older Turbocharger Resources?

If you’ve got a dog-eared turbocharging book from the late ’90s on your shelf, you’re not alone—but you might want to keep that bookmark handy for reference rather than gospel. The world of turbos isn’t exactly standing still. Over the past couple of decades, we’ve seen a tidal wave of advancements, from BorgWarner’s EFR line to Garret’s latest Gen II tech, and countless new compressor maps now fill up pages that didn’t even exist back in the day.

While some principles of forced induction remain the same, today’s turbos offer efficiencies, materials, and features the engineers of 1997 only dreamed about. So, if you want the most up-to-date info on things like boost control, transient response, or sizing for the latest compound setups, you’ll do better with current resources—fresh from manufacturers and recent tuning guides.

That doesn’t mean the classics are worthless—they’re great for fundamentals and a few time-tested tricks—but for specifics, especially when it comes to modern diesel and gas applications, newer sources will steer you in the right direction.

 

Are diesel turbos affordable and easy to rebuild?

Diesel Turbo Affordability and Rebuilds

Wondering if diesel turbos are a budget-friendly option, or if it’s possible to freshen one up in your own garage? Good news on both fronts. Compared to many gasoline counterparts, diesel turbos tend to be much less expensive to buy, and parts to service them—think BorgWarner or Holset kits—are usually widely available.

As far as rebuilding, you won’t need a wall full of exotic tools or a mechanical engineering degree. With basic hand tools, a propane torch, and a little patience, most folks can get a tired turbo spinning like new. There are even affordable rebuild kits for common models if you’d rather do the work yourself than hunt for a replacement. Just remember, attention to detail goes a long way toward making sure your refreshed turbo lives a second life—so take your time, follow the instructions, and keep things as clean as possible.

 

Can used OEM turbos from other vehicles be suitable for a custom turbo project?

Using OEM Turbos for Custom Builds

We’re often asked if a used OEM turbo from another vehicle is a good fit for your project. The truth? Sometimes yes, sometimes no. The fundamentals of turbocharger operation haven’t changed much over the years—what worked decades ago for moving air still works today.

If you’re looking for a straightforward solution, match your engine’s displacement and power goals with a factory turbo from a similar vehicle. For example, want 300–350 horsepower out of your 2.0L four-cylinder? Hunting down a turbo from a car with a comparable engine size and output, like those found in performance versions of Evos or STis, can get you in the ballpark.

However, it’s important to understand OEM turbos are generally designed for good spool and drivability at lower RPMs, rather than absolute power up top. That means they’re usually a bit conservative on flow. Once you start pushing them beyond stock settings, they tend to choke off airflow in the midrange—great for instant response, not so great if you’re chasing big horsepower.

Aftermarket options like those from Garrett or BorgWarner, on the other hand, are specifically engineered for higher volumes and sustained boost, making them better suited for larger power gains if you’re not willing to settle for just “good enough.”

So, while a used OEM turbo can be a cost-effective starting point and perfectly serviceable for moderate upgrades, be realistic about your goals and the limitations of stock hardware. If you’re chasing big numbers or planning to run higher RPMs, you’ll likely want to size up.

 

Are there more up-to-date resources available for turbocharger selection and technology compared to books from the 1990s and early 2000s?

Keeping Up with Turbo Technology

Turbochargers have come a long way since the 1990s. Back in the day, most of the turbo selection resources—like books from 1997 or early 2000s—were a solid starting point, but tech has sprinted ahead. Today, we’re spoiled with an incredible range of up-to-date compressor maps and turbo options, thanks to companies like BorgWarner, Garrett, Holset, and a host of others who are always dropping new tech into the market.

If you’re after the latest and greatest information, there’s a world of modern resources out there. Many turbo manufacturers publish detailed spec sheets, compressor maps, and sizing guides online that track the latest engineering—making it easier than ever to match a turbo to your needs. Forums, online calculators, and even YouTube channels from tuners and engineers shed light on the real-world performance of the latest models.

In a nutshell: While those classic books might still offer some foundational knowledge, turbocharging in 2024 is a whole new ballgame. For the sharpest info, lean on up-to-date manufacturer data and interactive web tools. That way, you’re not just chasing numbers—you’re using the best numbers available.

 

What are the typical exhaust gas temperature (EGT) limits for gas and diesel turbos?

Exhaust Gas Temperatures: Diesel vs. Gas Turbos

Now, what about exhaust gas temperatures (EGTs) for turbos? There’s a bit of a myth that diesel and gas turbos operate in totally different thermal realms, but the truth is a little more nuanced, and it matters if you want boost to last as long as your truck payments.

For diesel engines, most manufacturers and performance builders aim to keep sustained EGTs in the ballpark of 1,200–1,300°F during hard use. That’s the safe zone for longevity, and it’s what modern heavy-duty trucks are designed around to hit those famous half-million-mile marks. Push things above 1,300°F and you’re wandering into the upper end of “standard,” but not quite into “melt your wallet” territory yet. On the other hand, gas engines—especially high-performance turbocharged applications—see higher peak EGTs. Typical thresholds are just under 1,700°F for durability, with most OEMs expecting these turbos to survive at least 150,000 miles at those temps.

The interesting bit here? The turbine housings and wheels for both diesel and gas turbos often use similar nickel-based alloys (think Inconel and its cousins), although diesel setups run a bit cooler for the sake of long-haul reliability. While the raw materials aren’t drastically different, the design priorities are—diesels are all about marathon reliability, while gas turbos accept a little more thermal stress for short-term performance.

So, rule of thumb: diesel turbos like to keep it under 1,300°F for the long haul; gas turbos can flirt with 1,600–1,700°F but only if you don’t mind testing the limits.

 

What signs indicate that EGT issues are damaging a turbo, and what failures might occur?

EGT Issues and Turbo Damage

When exhaust gas temperatures (EGT) climb too high, your turbo will definitely let you know—though usually not in the way you’d prefer. One of the most recognizable symptoms is cracking in the turbine housing, sometimes showing up as hairline fractures or, in severe cases, full-on splits. Extreme heat takes a toll over time, even on materials like Inconel that are designed to resist these high temperatures.

Less common, but still possible, are failures inside the turbo itself. Blades can show signs of heat stress, though complete blade failure is rare thanks to the robust alloys used by companies like Garrett and BorgWarner. However, shaft seals are the real weak spot here; excessive EGTs can cause them to fail and lead to oil leaks, smoke, or loss of boost.

In short, if you’re seeing mysterious cracks on the turbo housing or notice oil where it shouldn’t be, it’s a good idea to check your EGTs and make sure things aren’t cooking beyond what your turbo can handle.

 

Are there recommended books or resources for learning about turbo sizing?

Recommended Resources for Turbo Sizing

If you’re looking to start your turbo knowledge on the right foot, the book “Maximum Boost” by Corky Bell is a staple in the world of forced induction. While the sections on engine management are starting to show their age, the foundational science and practical advice about turbochargers are just as relevant now as when it first hit the shelves.

For those who learn better by doing, there are countless online calculators and guides to help demystify the math behind turbo sizing. These tools often let you plug in your engine’s displacement and desired power output to suggest potential turbochargers—no slide rule required. If formulas start making your head spin, many enthusiasts also recommend looking at stock setups: find factory turbos paired with engines similar in size and power goals to yours. For example, if you’re targeting 300-350 horsepower out of a 2-liter engine, it’s a good bet that turbos from performance icons like the Evo or STi could fit the bill, since manufacturers have already matched them to comparable engines from the factory.

Just remember, most OEM turbos are built for smooth, responsive low-end power rather than big top-end numbers, so if you’re chasing dyno glory, you may want to look beyond what the factory bolted on.

For the academics at heart, many technical school curricula or independent educators have crafted step-by-step guides to walk you through the selection process. These resources often break it all down into manageable pieces, making seemingly complex numbers and ratios feel a lot more approachable.

 

Are there criticisms or limitations to the information in older turbocharging books like “Maximum Boost”?

Limitations of Older Turbocharging References

If you’ve spent any time hunting down info on turbocharging, chances are you’ve run across “Maximum Boost.” It’s a solid starting point for background knowledge; however, it’s worth noting where these older resources start to show their age. First off, technology has marched on at a rapid pace—since the original publication back in the late ‘90s (and even the early 2000s updates), the landscape of available turbos, from both diesel and gas applications, has exploded.

That means some of the compressor maps and sizing recommendations in these books are a bit, well, outdated compared to what’s available today. Since then, manufacturers have developed a multitude of new turbines, compressor wheels, and variable-geometry options that simply weren’t on the radar back then.

So, while a trusty turbo book might give you a solid foundation and help explain the math, you’ll still want to break out those online calculators, spreadsheet tools, and—most importantly—the current turbo maps from brands like Garrett and BorgWarner before making any decisions. Modern resources will help you cut through the noise and find solutions tailored to the kind of power and efficiency today’s engines can deliver.

And hey, if you stumble into the section on intercooler design in one of those old tomes, maybe don’t take it as gospel—it’s okay, even the experts update their stance once in a while.

 

Are there significant risks or failure rates when running diesel turbos on gasoline engines?

Diesel Turbos on Gas Engines—Is There a Catch?

We get asked a lot whether running a diesel turbo on a gas engine is asking for trouble. The reality? There’s not much to worry about. Turbos like the Garrett and BorgWarner models have been bolted onto everything from diesel workhorses to sporty gasoline builds for years without drama.

Sure, there are some differences in exhaust temperature and flow characteristics between the two engine types, but the turbochargers themselves are robust and more than up to the task. It’s more important to make sure you’re matching the turbo’s size and flow to your horsepower goals and not overspeeding or overboosting it—regardless of what’s feeding it fuel.

Bottom line: failures tied directly to running a diesel-spec turbo on a gas setup are rare. As long as you get your sizing and tuning right, you’ll enjoy the benefits (and the boost) just like thousands of hot rodders and fabricators have before you.

 

How do the materials and construction of diesel and gasoline turbochargers compare?

Diesel vs. Gasoline Turbocharger Materials

When it comes to the guts of a turbocharger—whether it’s found spinning on a diesel or a gasoline engine—most people are surprised to learn that the materials and construction aren’t all that different. Modern turbos, from reputable brands like Garrett or BorgWarner, are typically built with similar grades of cast iron or steel for the turbine housing, high-nickel alloys in hot sections, and robust aluminum or steel for the compressor side.

Where you’ll spot a difference is in the operating environment. Gasoline engines routinely see much higher exhaust gas temperatures (EGTs)—often 1,300°F and beyond—compared to diesels, which generally live closer to 1,200°F under load. This means that while the basic architecture is similar, some gasoline applications might upgrade to more exotic alloys (think Inconel or Mar-M) for added durability at extreme temps.

But don’t get the wrong idea: diesel turbochargers are still built to take a beating. They’re often designed with longevity in mind, aiming for extended service intervals—think 500,000 miles or more. Gasoline turbos, especially in performance cars, might target lower mileage before overhaul, usually in the 150,000-mile ballpark. However, if a gas turbo fails before this, odds are good the OEM will be footing the bill under warranty.

The bottom line? Most of the “major” differences come down to target longevity and the maximum temperature each turbo is expected to handle, not a wholesale change in the quality or basic recipe of materials.

 

Are diesel turbos suitable for use on gasoline engines, and what are the potential issues?

Diesel Turbos on Gas Engines: Worth the Swap?

We get this one a lot: can you bolt a diesel turbo onto your gasoline project and call it a day? Short answer—it’s not always that simple. While the basic design of most turbos (think Garrett, BorgWarner, Holset) is pretty similar on the surface, it’s what’s inside that counts—especially when we’re talking EGTs (exhaust gas temperatures).

Diesel turbos are engineered for longevity, with some trucks expected to rack up half a million miles (or more!) between rebuilds. That means they’re typically optimized for exhaust temps in the neighborhood of 1200-1300°F, where diesels spend most of their working life. Gasoline engines, on the other hand, routinely push 1500°F or more, especially under boost. While some gas turbo applications get away with even higher temps (think race cars or hot street builds), the point is, the heat can add up fast.

Now, you’d expect turbo manufacturers to sweat the details, and for the most part, materials like cast iron or even high-nickel alloys (some folks are even casting turbine housings out of Inconel) do a good job keeping up with the heat. But the devil’s in the details—gasser turbos might feature tweaks for coolant flow, bearing choices, or housing metallurgy that help them survive at those higher EGTs. Even though diesel and gasoline turbos might share DNA, gas units have to survive tougher thermal abuse, usually with a design life around 150,000 miles. If they consistently grenade before then, the OEM is writing checks.

Bottom line? For a wild Friday night build, you might get away with a diesel turbo—but if you plan to push serious EGTs and want OE-level reliability, it pays to spec a turbo built for gasoline heat. No one likes surprise shrapnel in the downpipe!

 

Is “Maximum Boost” a good resource for learning about turbocharging?

Is “Maximum Boost” Still Worth Reading?

When it comes to learning the science of turbocharging, “Maximum Boost” by Corky Bell often comes up as a classic reference. If you’re just starting out, the book does a solid job laying down the principles and explaining the nuts and bolts behind how turbochargers work. It’s like the old Chilton’s manual in your grandpa’s garage—plenty of foundational info, but don’t expect a roadmap for the latest tech.

That said, keep in mind that the book was written back in the late ’90s. Turbo technology has had quite the growth spurt since then. Today’s performance world is flooded with new (and improved) turbo designs, more advanced materials, and almost endless compressor maps—not to mention all the online calculators and software at your fingertips.

If you’re the hands-on type, consider pairing your reading with a spreadsheet and a few online tools to help translate Corky’s methods into modern-day numbers. While “Maximum Boost” gives you the building blocks, you’ll want to supplement it with up-to-date resources and maybe skip a chapter or two—its take on intercooler design, for example, is a bit dated.

All in all, it’s not the turbo bible, but it’s a perfectly good place to start. Just be ready to do a little homework to bring its advice into the 21st century.

 

What are the pros and cons of using a diesel turbo on a gasoline engine?

Diesel Turbos on Gas Engines: Pros and Cons

If you’ve ever wandered into a dark corner of an internet forum, you’ve probably seen folks debating whether you can bolt a diesel turbo onto a gasoline engine. Let’s break it down.

The Pros

• Flow Capacity: Diesel turbos are designed to move a lot of air, usually for big-displacement engines. If your gas engine is relatively small but you’re aiming for big boost at high RPM, a diesel turbo off, say, a 6-liter engine might deliver the airflow you want for your 3-liter at double the RPM.
• Built for Durability: These turbos are made to handle high pressure ratios and heavy-duty cycles. They’re nicely overbuilt, which can be a plus when you’re pushing the limits.

The Cons

• EGT Tolerance: Now, here’s the rub. Diesel exhaust gas temperatures (EGTs) are typically much lower than those of gasoline engines. Run a diesel turbo on a gasser, and you might see turbine housings crack or seals give up the ghost if things get too toasty. While turbine blades are often made with Inconel or other heat-resistant alloys, the overall design just isn’t set up for higher gas EGTs day after day.
• Response Time: Diesel turbos are often sized for engines that live in the low-to-mid RPM range. Plopping one on your free-revving gas project may mean extra lag before you feel the boost.
• Physical Size and Weight: Diesel turbos are usually hefty units, sometimes much heavier than a typical gasoline turbo. Not a dealbreaker, but it’s worth keeping in mind—especially if you’re comparing your options to featherweight aftermarket choices from Garrett or BorgWarner.

You won’t always spot EGT warnings in most spec sheets, but it’s a real-world concern. Push too hard, and you risk heat damage long term, even if the turbo itself doesn’t grenade on day one.

So, in summary: diesel turbos can work, but it’s not a straight swap. You’ll want to watch your EGTs, consider the response characteristics for your intended use, and factor in the physical heft of these brutes before you start bolting one on.

 

How reliable and effective are Holset HX35 turbos when used on gasoline engines?

Holset HX35 Turbos on Gas Engines

Now, if you’re wondering whether Holset HX35 turbos play nicely with gasoline engines, the answer is a resounding yes. These turbos have been shoehorned onto just about every four-cylinder combination you can imagine, and they seem to thrive no matter the fuel type. They’re inexpensive, durable, and have a reputation for turning even the most humble inline-four into something that pulls like a freight train hopped up on caffeine.

The best part? Reliability isn’t really an issue—Holset HX35s have racked up miles on gas builds for years, and you’d be hard-pressed to find widespread failures linked to swapping them from diesel to gas. Their abundance on the used market means you can find one in just about any junkyard, and you can enjoy proven performance without breaking the bank. For budget-minded builds looking for serious boost, it’s tough to go wrong here.

 

How important is compressor map efficiency in turbo selection?

Figuring out exactly how much a turbo will flow requires a bit of help from the manufacturer. Companies like Garrett and BorgWarner provide access to compressor maps, which show the maximum pressure ratio, flow, and compressor speed. When reading these maps, keep in mind that operating in less efficient regions—those far from the map’s “sweet spot”—can lead to higher discharge temperatures. This is because the turbo is working harder outside its optimal efficiency range, which not only affects performance but could also put more stress on your engine’s components. So, while compressor maps are invaluable tools, understanding where your setup falls on that map is just as important for keeping things cool and reliable.

 

What practical impact does compressor map efficiency have on turbocharger and engine performance?

When a turbo runs in an inefficient area, the resulting hotter air charge can reduce power output, increase the likelihood of engine knock, and put additional stress on the intercooling system.

 

Why is compressor map efficiency important when selecting a turbo?

Efficiency matters because it directly influences how much the air is heated during compression. Staying within the efficient region of the map helps keep discharge temperatures lower, which is better for both power and engine longevity.

 

What are the consequences of running a turbo in a less efficient area of the compressor map?

Operating a turbo outside of its peak efficiency zone leads to increased air temperatures at the outlet, which can negatively affect engine performance and reliability.

 

Why is it important to specify engine requirements (displacement, power goal, desired spool characteristics) when selecting a used turbo?

While turbo sizing is crucial, it’s important to remember that other engine modifications can significantly impact turbo performance. For optimal engine performance, the air and fuel your engine consumes must be balanced. If you decide to increase fueling with larger injectors or a dual injection pump, you must also increase airflow. Failing to do so could lead to issues like high exhaust gas temperatures (EGT), which compromise engine efficiency.

Imagine a turbo that’s perfectly matched with a stock fuel system. With a set of larger injectors and a high-performance tune, that same turbo might be too small, unable to provide the necessary airflow. When upgrading, consider installing a larger turbo first and keeping the stock fuel system. This approach minimizes risks and ensures smoother transitions between modifications.

When searching for a used OEM turbo, it pays to be specific about your requirements—consider your engine’s displacement, your power goals, and how much you care about spool time. The more detailed your needs, the easier it is to narrow down which vehicles may have a suitable turbo to salvage and adapt. Defining these parameters up front makes it much simpler to select the right turbo for your build, saving you time, effort, and a few headaches down the road.

 

What information do I need to gather before asking for turbo recommendations?

Before seeking recommendations, you should know your engine’s displacement, your power goals, and your preferences regarding spool characteristics, such as whether you want power to come on early or are aiming for peak output at higher RPMs.

 

How does the specificity of my requirements affect the turbo selection process?

The more precise you are with your requirements, the easier it is to identify a turbo that fits your needs. Being detailed allows for a more targeted search, increasing the chances of finding the ideal turbo for your application instead of settling for something merely close.

 

Why do I need to provide detailed engine requirements (displacement, power goal, desired spool characteristics) when looking for a used OEM turbo?

Providing detailed information about your engine helps ensure that any turbo suggestions are actually compatible with your goals and setup. Without knowing things like displacement, desired power, and how quickly you want the turbo to spool, recommendations may be off the mark and not suited to your project.

 

How should you go about choosing the best turbocharger based on cost, availability, and performance?

Turbos and Airflow

We get the question all the time: how do you size turbochargers? In reality, the answer is simple: turbos should be sized as small as possible for your desired horsepower. Luckily, airflow is one of those rare areas where the stars align, as roughly one pound per minute (lb/min) of air is equal to about 8 rear-wheel horsepower on a good running engine. That means a turbo that can flow 50 lb/min (we’re talking stock-ish here) would be good to about 400rwhp. For those looking to be right at 1,000rwhp, an S480 is a popular choice, which at 120 lb/min (120 x 8 = 960 rwhp) we can see why. Note that it’s also popular to make more power than the “formula,” but if you do, it’s usually at the risk of overspeeding the turbo.

For those venturing into the race truck realm, where horsepower exceeds 850, choosing the right turbo setup becomes even more critical. At these elevated levels, a single S400-based 80mm turbo can be a gateway to 1,000 horsepower, while a compound setup with a larger 106mm turbo can push into the 2,000-horsepower range. This choice depends heavily on whether you prioritize peak power or a balanced performance across various conditions.

A Little Math Goes a Long Way

From here, it’s a matter of math and maps—specifically, turbo compressor maps. Finding the best compromise between cost, availability, and performance means taking the time to look at these maps and do a bit of calculating. Don’t let the graphs intimidate you: matching your engine’s airflow needs to the turbo’s efficiency island is where you’ll find the sweet spot. If you’re new to this, consider reading up on the fundamentals, then play around with online calculators or even create a simple spreadsheet. This hands-on approach not only demystifies the process but also helps you visualize how different combinations will affect your build, whether you’re chasing a certain horsepower or optimizing for daily drivability.

Compound Turbo Considerations

Compound turbos can be a bit more difficult to size than single turbos, and can be geared towards response, all-around performance, or peak power. In general, the larger turbo should flow roughly twice what the small turbo will flow. This setup is perfect for those seeking a balance between quick spool-up and maximum power output. So, as you map out your ideal turbo configuration, remember: a little time spent with the numbers and a few digital tools can make all the difference between “good enough” and “just right.”

 

How can you use tools to aid your turbo selection process?

Leverage resources like online turbo calculators or even a simple spreadsheet. These tools help you plug in different numbers for cost, airflow, and horsepower to see which turbo offers the best blend of price, availability, and performance for your application.

 

What practical steps should you take to make an informed turbocharger choice?

To make a well-informed decision, start by educating yourself—read up on the basics and specifics of turbo sizing. Then, use concrete data and comparisons to narrow down your options, rather than going by guesswork or hearsay.

 

How do you balance cost, availability, and performance when choosing a turbocharger?

When selecting a turbocharger, it’s important to weigh not only the horsepower and airflow requirements but also the price and how easy it is to actually get your hands on the desired model. The best choice often involves finding a middle ground between what you can afford, what’s in stock, and what will deliver the performance you’re after.

 

What resources or methods can be used to determine the best turbo for a specific application?

Figuring out exactly how much a turbo will flow requires a bit of help from the manufacturer. Companies like Garrett and BorgWarner provide access to compressor maps, which show the maximum pressure ratio, flow, and compressor speed.

Once you’ve got your hands on these maps, it’s time to break out a little math. By studying different turbo maps, you can weigh your options and find the sweet spot between cost, availability, and performance. Online calculators and spreadsheets are handy tools for crunching the numbers and visualizing how various turbos might perform on your setup.

Keep in mind, though, that while foundational resources like Corky Bell’s Maximum Boost offer great theoretical background, some information—especially regarding available turbos—may be dated. The turbo market has changed rapidly over the last couple of decades, so supplement your research with current maps and data you can find online. In short: use classic books to learn the theory, but always double-check with up-to-date resources to make sure you’re not missing out on newer, better options.

 

How should one approach the process if there are conflicting opinions or errors in resources?

Approach all resources with a healthy dose of skepticism. If you encounter conflicting advice or potential errors—something occasionally spotted even in well-respected books—cross-check information with additional sources, such as online forums or updated technical guides, to arrive at well-rounded conclusions.

 

Are there limitations or pitfalls in relying solely on older published materials?

Relying only on older references can leave you behind, as they won’t include the many new turbocharger models or the latest industry developments. It’s important to supplement classic resources with current information to ensure your decisions are based on the full range of available options.

 

Where can up-to-date turbocharger compressor maps be found?

The most current compressor maps are often available directly from manufacturers’ websites and various online sources. Given the rapid evolution in turbocharger technology, searching the internet will provide access to the latest information.

 

How should different resources be combined or used together?

Start by using books like “Maximum Boost” to grasp the core principles behind turbocharger operation. After that, apply what you’ve learned by consulting up-to-date compressor maps online, and leverage spreadsheets or online calculators to analyze your options based on real-world data.

 

Is “Maximum Boost” by Corky Bell still a useful resource?

“Maximum Boost” remains a solid introduction to turbocharger theory, but keep in mind that it was published in the late 1990s. While the foundational concepts are still relevant, the book doesn’t cover the latest advancements or the broader selection of modern turbos that have come to market since its release.

 

How do OEM turbo setups differ from aftermarket or custom turbo configurations in performance goals?

Turbo Options for High-Performance Diesel Trucks

When transforming your diesel truck into a speed and performance machine, turbo upgrades play a critical role. For enthusiasts who prioritize acceleration and power over utility, several turbo options are available, each with its unique advantages. But before you simply “go big or go home,” it’s important to consider how your intended use and the rest of your truck’s setup will affect your ideal turbo choice. The right setup isn’t always about chasing the biggest number—it’s about finding the balance that best fits your driving style.

Variable Geometry Turbo (VGT) Upgrades

For those looking to maintain some versatility without compromising on performance, upgrading to a larger VGT is a popular choice. These turbos, like those in the 67mm family, offer improved airflow and can significantly boost your horsepower, pushing you past the 700hp mark. They are ideal for 5.9 or 6.7 Cummins engines and similar setups. VGTs provide a broad powerband and are relatively simple to install as drop-in replacements.

A well-sized VGT can offer that satisfying punch of instant torque while still carrying you through most of the rev range. However, it’s wise not to select a turbo so small that you’re already 1000 rpm past peak boost in the next gear after shifting at redline. On the flip side, if you’re building a dyno queen or a truck that lives at the upper end of the tach, a larger turbo that really comes alive just before redline could be right up your alley.

Fixed Vane Turbochargers

If you’re aiming for peak horsepower and are less concerned with low-end torque, a single fixed vane turbocharger might be the way to go. Although these turbos may lack the wide powerband of a variable geometry system, their free-flowing exhaust housings make them excellent for high-performance builds. Options are available that can handle up to 67mm and beyond, delivering impressive power with reduced exhaust gas temperatures (EGT).

OEMs often choose small, quick-spooling turbos to make their trucks feel lively off the line, but these tend to run out of steam well before redline. A performance-focused fixed vane setup, on the other hand, trades some of that low-end snap for top-end rush, making sure your power doesn’t fizzle out just when things are getting exciting.

Turbo Kits and Conversions

For serious truck enthusiasts, complete turbo kits that convert your existing setup into a high-performance beast are available. These kits often include different turbo sizes, ranging up to 72mm, catering specifically to brands like Cummins or Powerstroke engines. While these installations might demand more effort, the resultant power gain and performance enhancement make the investment worthwhile.

If you’re after the “all-around” turbo, look for one that’s just big enough to maintain strong boost almost to redline, but not so large that you’re waiting all day for it to spool. The sweet spot is a turbo that holds its own right until you reach the upper end of your rev range, giving you that perfect blend of responsiveness and top-end pull.

Performance Considerations

When choosing the right turbo for your truck, consider what aspects of performance are most critical to your driving needs. Whether you opt for a VGT for its ease and versatility or a fixed vane turbo for its robust power output, preparing your vehicle with larger injectors, a more powerful fuel injection system, and supportive engine modifications will help maximize your gains.

So, whether you’re building a street beast, a dyno monster, or something that needs to deliver everywhere in between, your turbo choice should reflect how and where you want to make your power. In summary, turbo options for those focused on speed and performance range from sizable VGT upgrades for balanced power and ease of use to high-output fixed vane turbos for pure horsepower. Each choice offers distinct advantages depending on your specific performance goals—and finding the right match can mean the difference between a truck that feels quick everywhere and one that only comes alive at the very edge.

 

What happens if a turbo is sized too small or too large for a particular setup?

If a turbo is too small, it may provide strong boost at low RPMs but run out of capacity before redline, limiting high-speed performance. If it’s too large, the engine might not build sufficient boost until very high RPMs, making the vehicle sluggish at lower speeds and only coming alive near the engine’s limit.

 

What are the trade-offs between quick response and high power in turbo sizing?

A smaller turbocharger delivers boost earlier, offering sharp acceleration from a standstill but may not sustain power as RPMs climb. Conversely, a larger turbo produces more power at the top of the rev range but typically exhibits more turbo lag, meaning slower boost response at low speeds.

 

How do OEM and aftermarket turbos differ in their performance characteristics?

OEM turbos tend to be smaller, which helps them build boost rapidly and provide strong low-end torque, but they often lose effectiveness as engine speed increases. Aftermarket turbos, especially larger ones, can maintain or increase power at higher RPMs, though they may take longer to reach full boost.

 

What are the main goals of OEM turbos versus custom/aftermarket turbos?

Factory-installed turbos are usually designed to deliver quick throttle response and make the vehicle feel lively during normal driving. In contrast, aftermarket or custom setups often aim to maximize power output and performance at higher RPMs, sometimes sacrificing immediate low-end response for greater top-end strength.

 

Is it necessary to build the engine before selecting and buying a turbo?

However, achieving such high power doesn’t stop at the turbos. You’ll need a fortified engine with stronger pistons and rods, a performance camshaft, and a robust valvetrain. A massive fuel system is essential to support these modifications, and a built transmission is critical to handle the immense stress.

Before you even get to the point of bolting on a turbo, you’ll want to make sure your engine is already built to take the boost. Sizing the right turbo can be tricky—there’s no one-size-fits-all solution, and grabbing a used turbo off the shelf might seem tempting, but it’s important to do your homework first. Whether you’re trawling through forums, digging into technical books, or scouring online guides, the consensus is clear: build the engine to your power goals first, then match the turbo to the setup. This approach saves you from expensive mistakes and ensures all your supporting mods work in harmony, rather than becoming the weak link in the chain.

 

Is it possible to use a used turbo instead of a custom one, and how would that affect the process?

It’s certainly an option to source a used turbo for your project, which can save money and still deliver great results if the turbo is in good condition and fits your application. However, you’ll need to pay close attention to its specifications to be sure it matches your engine’s needs. Sometimes, adapting a used turbo requires creative solutions or additional fabrication compared to a custom-made setup.

 

Where can I learn more about properly sizing a turbo for my engine? Are there recommended resources (links or books) for turbo sizing?

There are plenty of books and online resources dedicated to turbocharging and proper sizing. Look for well-reviewed titles on automotive forced induction or forums where experienced builders share advice and calculators to guide your selection. Technical guides from respected manufacturers can also be invaluable.

 

Is it necessary to build the engine before selecting and buying a turbo?

While you don’t have to completely finish building your engine before picking out a turbo, you’ll need to have a clear idea of your engine’s capabilities—such as its displacement, compression ratio, and intended power output—before you can properly match a turbo to it. Many builders recommend planning your turbo and engine build together so that each component complements the other.

 

How does intercooler size and weight factor into overall turbo system performance?

Engine airflow math is fairly simple (with some exceptions, like intercooling), but fueling is a tough one to crack. Intercooler sizing, for example, seems straightforward until you consider the weight penalty. On slower cars—say, anything running 11 seconds or more in the quarter mile—installing a larger intercooler and its piping doesn’t have a huge downside; if your setup adds 30 pounds, you only need to see a gain of about 3.1 horsepower to actually go quicker.

Move up to an 8.90-second car, and the story changes: now you’re using around 7.9 horsepower just to haul that intercooler package down the track. Still, in most cases, the temperature drop and resulting power increase from a bigger intercooler more than make up for the added mass. The real constraint is usually packaging—just fitting the thing under the hood or behind the bumper. So, as long as you can make it fit, bigger is almost always better when it comes to intercoolers.

 

What is the main limit on intercooler size in practice?

The primary constraint is often not the weight, but rather how much space you have to fit the intercooler in your vehicle—packaging is usually the greater limitation.

 

Should you always choose the largest intercooler?

Generally, yes—choosing a larger intercooler is beneficial because the improved cooling and corresponding power gain typically outweigh any drawbacks from the extra weight.

 

Does the power gain from cooling outweigh the weight penalty?

In most cases, yes. If the intercooler’s cooling effect results in a power increase that exceeds the power required to move its added weight, the net effect is a quicker car.

 

What is the horsepower “cost” of carrying a heavier intercooler, and what are the numbers?

For a car running an 11.90-second quarter mile, moving a 30-pound intercooler and piping setup uses about 3.1 horsepower. In a much faster 8.90-second car, that same component demands roughly 7.9 horsepower just to carry the extra weight down the track.

 

How does intercooler weight affect performance in cars of different speeds?

The heavier the intercooler, the more power is required to accelerate that extra mass, and this effect is more pronounced in faster cars. While a weight increase may barely impact slower vehicles, it can become a significant performance penalty for cars running quicker quarter-mile times.

 

What potential issues can arise from high exhaust gas temperatures (EGT) when using diesel turbos on gasoline engines?

While turbo sizing is crucial, it’s important to remember that other engine modifications can significantly impact turbo performance. For optimal engine performance, the air and fuel your engine consumes must be balanced. If you decide to increase fueling with larger injectors or a dual injection pump, you must also increase airflow. Failing to do so could lead to issues like high exhaust gas temperatures (EGT), which compromise engine efficiency.

High EGT isn’t just a number on a gauge—it can have real mechanical consequences. For example, persistently elevated EGT can cause cracking of turbine housings, a headache no one wants to deal with. While turbine blade failures are less common these days (thanks in large part to the widespread use of Inconel alloys in the industry), another potential trouble spot is the shaft seal, which is more susceptible to failure under excessive heat. Balancing fueling and airflow isn’t just about making power—it’s about keeping your turbo and engine components in one happy, un-cracked piece.

 

What are the failure modes of turbo components under high EGT?

Under sustained high EGT, turbine housings may develop cracks due to thermal expansion and contraction, turbine blades could deform or fracture if not made from suitable materials, and shaft seals might degrade or fail altogether, leading to oil leaks or loss of boost pressure.

 

How do turbo materials affect susceptibility to failure?

The use of high-grade alloys, such as Inconel, in turbine blades greatly reduces the likelihood of blade failure from excessive heat, as these materials are engineered to withstand extreme temperatures.

 

Which failures are more or less likely, and why?

Shaft seal failures are more probable under high heat conditions, while turbine blade failures are less common due to the widespread use of advanced, heat-resistant materials in their construction.

 

What specific turbo failures can high EGT cause?

High exhaust gas temperatures can lead to physical damage within the turbocharger, including cracks developing in the turbine housing, failures of the turbine blades, and possible breakdowns of the shaft seals.

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