More Power, Less EGT, and Greater Reliability
Perhaps some of the most underrated performance parts in the industry are water-methanol injection systems. On street trucks, a well-tuned water-meth system can be worth 75 horsepower or more, as well as a drop in exhaust gas temperatures of 100 to 300 degrees. In competition applications, huge engine-driven water injection systems can reduce exhaust gas temperatures by up to 1,000 degrees and also allow for more aggressive tunes. So—it’s safer—with more power? That is correct.
How Water Injection Works
As an engine makes more power, it also makes more heat. Eventually, combustion temperatures and exhaust gas temperatures, EGT, can reach dangerous levels, and that’s where water injection comes in. Even with efficient intercooling, diesel engines found in high-horsepower street applications or racing vehicles will still need additional cooling. When water is injected into the engine, it is converted to steam, and when this happens, it absorbs an enormous amount of heat out of the air. This function is called the latent heat of vaporization, and reduces both combustion and exhaust gas temperatures without having much of an effect on power.
Adding Methanol to Create Water-Methanol injection
At some point, an innovative gearhead figured out that you could make some extra power with water injection just by mixing it with methanol. Not only does methanol have a latent heat of vaporization value all of its own, it also is a fuel, so it makes power when it is injected into an engine. Since diesel engines are compression-ignition engines, introducing a fuel into the intake may seem dangerous; but that’s the beauty of the water-methanol mix. If 100-percent methanol was injected into a diesel, either a dangerous backfire, or engine-damaging pre-ignition (which normally isn’t possible in a diesel) would occur, resulting in some fried parts. The water component in water-methanol injection acts like a detonation inhibitor, and keeps the methanol from auto-igniting under the high compression temperatures of a diesel. While it seems that a 50/50 mix is a good safe ratio for cooling and power, we have heard of folks going as high as 70 percent methanol, which sometimes works (lots of power) and sometimes doesn’t (engine damage).
Street-Oriented Water-Methanol Injection Kits
Adding fuel is the easiest way to extract more power out of a street-driven diesel, and even with just basic tuning, exhaust gas temperatures can reach the point where they are at dangerous levels. A stock Duramax engine for instance, will only generate about 1,300 degrees of exhaust gas temperature (which is safe) but we’ve seen tuned engines that have peaked at 1,800 degrees or even higher. With this type of heat, it’s only a matter of time before damage occurs.
“On street trucks, a water-meth system can be worth 75 horsepower or more, as well as a drop in exhaust gas temperatures of 100 to 300 degrees”
While increasing turbocharger size or intercooler efficiency is a good way of keeping exhaust gas temperatures under control while adding power, we’ve also seen good results with water-methanol injection. With a 50/50 mix, average gains in power are usually between 35 hp and 75 hp, with a 150 to 300-degree drop in EGT. Having these systems triggered at part throttle on aggressive tunes can also result in greater towing speeds, as more throttle can be applied, while keeping EGTs in or below the 1,200 to 1,300 degree “safe” zone for diesels.
Injecting a bunch of water or a water-methanol mix at low boost or rpm can result in “snuffing” the engine out. Essentially, there’s too much water compared to fuel and air, so the engine stops running. With this in mind, builders have integrated different forms of control into water-methanol systems to ramp up the level of injection as boost and rpm rises. The simplest form of activation is a pressure switch, like a Hobbes switch, which will trigger the system at a certain pre-set amount of boost. Up from there are throttle-position triggers, digital controllers, and boost and EGT-based systems.
Injection systems vary in flow, controls, and options, and you’re probably not going to need a sophisticated multi-stage system just to cool down an old IDI for towing use. By the same token, a street-based kit probably won’t be enough for a 1,500 horsepower sled puller, so matching the kit to the application is an important part of selecting a system.
“In competition applications, water injection systems can reduce exhaust gas temperatures by up to 1,000 degrees”
Is Water/Methanol Injection Right for Me?
There are plenty of diesels in the 300 to 500 rear-wheel horsepower range, and water-methanol injection will work quite well on just about every one of those trucks. In competition applications, we’re surprised more folks outside of sled pulling (like fast-street and drag trucks) don’t run water or water-methanol systems, as replacing pistons, turbines, and other hard parts get expensive. If you’re looking for a little extra power or cooling, a water-methanol injection system might be just what the doctor ordered for your diesel. DW
High horsepower applications have their own unique set of problems when it comes to cooling. When it comes to trying to keep exhaust gases under control on a 2,000 to 3,000 horsepower diesel, a lot of water has to be injected into the engine, well past what most street kits are capable of delivering. While pickup truck systems may inject water at 200 to 300psi, it’s not uncommon for competition water systems to run at 800 to 1,000psi, with up to 12 delivery nozzles. If a water system fails in this type of application, EGTs can rocket past 2,000 degrees in a matter of seconds, so water injection is an integral part of keeping these engines alive.