The ABC's of Gauges Early Warning is the Name of the Game
The trick is to know which gauge designs are most appropriate, decide how accurate you need them to be, and understand how design affects cost.
To help us with the basics, we asked Jennifer Dandekar at Di/Pricol a few basic questions. Di/Pricol has a line of heavy duty gauges specifically for working trucks like diesels. Why? “A diesel gauge should be different from a gas powered vehicle’s gauge,” she says, “in several ways. They should have different ranges than gas vehicles, normally somewhat lower. Also, everything is a little rougher in a working truck, so you want a heavier-duty gauge.” She advises diesel truck owners to look for construction features that make gauges resistant to wear and tear, with metal cases, sealed crystals, powder coated metals, and anti-fog, anti-glare qualities.
If you don’t have one already, another diesel-specific gauge, the pyrometer, is probably the first gauge that should be on your list. “By far, the number one most important gauge everybody should have is the pyrometer,” she says, “because everyone needs to keep track of exhaust temps. It will tell you everything about what is going on.” Styling is another factor. Most gauges are available in a variety of ranges, colors. Very often they can be chosen to match lighting, dial face and needle color combinations used by OE manufacturers, so the new gauges do not have to appear tacked-on. “It’s not cheap to have gauges installed, so you want them to look good,” Jennifer notes. Clean installation is everything; it’s even possible to wire gauges so their brightness matches the rest of the dash.
Aside from the appearance, there are some differences in what’s behind the face. There are two main movements behind the dials, Air Core and Stepper Motor. The Stepper Motor movement is more like a watch, moving according to small amounts of input. These can be extremely accurate, but generally more expensive.
Air Core movements also enjoy substantial availability. These might be somewhat less accurate than Stepper Motor movements, but there are some applications in which extreme accuracy is not required, and Air Core gauges are less expensive. Other price differences can be based on how the gauge gets information. For example, a mechanical boost gauge, which uses a vacuum line as a source of input, might cost $50, but an electric gauge could cost around $200. Many gauge companies offer both. For motorsports where extreme vibration hampers accurate readings, some companies offer liquid-filled faces. These help keep the needle from bouncing around; the trade-off is slower reaction time.
Another option would be to use electronic, digital microprocessor-based readouts to provide the monitoring function of gauges. Many tuning systems and power modules are available with in-cab digital readouts that interpret the OE senders, or add new sensors, to provide feedback. These can do double-duty as a performance management tool, but there are limitations. We’ve talked to people who feel that a LED readout provides fastest recognition, but there are also those who prefer the indication of a brightly lit needle over presentation of a number.
Proper installation is a factor in getting accurate readouts. Fortunately, there are installation kits available for most types of gauges, so a careful, reasonably well equipped driveway mechanic can often make a clean installation. To get an idea of what’s involved, see our how-to on page 92 of this issue. Meanwhile, here is a quick list of the types of gauges generally available, and why you might need them. EGT (pyrometer)
Especially if you have a tuner installed or are adding fuel, the EGT gauge is a crucial window into how far you can take it before the worse should occur. Even if you have not, the slim margin of error on stock diesels that are worked hard means that a pyrometer is recommended for everybody. The actual reading could depend on where the pyrometer is installed, but generally, sustained readings over 1,200° would be about as high as you’d ever want to see. After that, all kinds of bad things begin to happen, including piston damage. However, pyrometers are available in ranges up to 1,600°, or even 2,000°, because there are brief moments when EGTs might spike to that level, and if that’s happening, you want to know about it.
Generally speaking, you would install the pyrometer on the driver’s side exhaust, before the turbo, to get accurate results, but access varies by make and model, and sometimes compromises have to be made. As a result, Jennifer tells us, “everyone has their own preferred method, but as a general rule, the cleaner the better.” Once you have your gauge, if you see consistently high exhaust gas temps, it could mean you are over-fueling at peak demand, in which case adding more air (turbo) or cooler air (charge-air cooler; water/meth injection) would help.
Transmission Temperature
If you’re upgrading your engine, or doing heavy towing, another advisable tool for avoiding catastrophic repair bills is a transmission temp gauge. This would be especially true for those who work their trucks hard at low speeds, as in off-road use, or towing in traffic. A good gauge will also tell you if you need an additional trans cooler, or if the cooler you have is good enough. Generally, about 220°F is where danger begins; after that the fluid begins to cook and the plastic and fiber pieces inside the transmission start to go south.
Boost
It’s not unusual for a tuned diesel to make more boost than the factory gauge can register. There are aftermarket boost gauges that show boost up to 90 psi and beyond; you should select one that has the most appropriate range for your setup. This is everyone’s favorite gauge to watch, because it moves around so much, but it’s there to tell you how well you are building boost. The boost gauge, like a vacuum gauge, can also help you get better mileage in ordinary driving. (To get better fuel economy, stay out of the boost!) Mechanical boost gauges require tapping a vacuum line into a source of boost, usually just in front of the turbo or before the MAP sensor. There are kits with the fittings and instructions that are pretty explicit for use with mechanical boost gauges. Electric gauges require no vacuum lines.
Coolant Temp
If you’ve had trouble with overheating — if you are running a swapped-in engine with a compromised radiator core setup, for example — a coolant temperature gauge might provide peace of mind. Even if you’re not, a good gauge can tell you if your thermostat is stuck open, or stuck closed, and how efficient your cooling system is overall. To get the best readings, usually you can install the sender into ports on the water pump or coolant filter. Best to avoid using the radiator itself because it is under pressure.
Axle Temp
For a working truck, especially those with enhanced powerplants, it’s entirely possible to cook the rear axle. Even synthetic oils will tend to oxidize at higher temperatures. Around 250°F. the additives will break down, and heat quickly builds with speed and load. Look for temps no higher than 225° continuous. One way to help keep a marginal axle alive is install an aftermarket diff cover that has more cooling surface and more fluid capacity. Many of these also have a spot specifically to mount the temp sender, which allows easier installation. In addition, sometimes finding the right gear lube for the axle, given the workload and season, can involve trial and error. Adding an axle oil temp gauge allows you to see how quickly the gear oil warms up, so you know if you have the right oil for the season.
Fuel Pressure
This is the gauge that tells you if you are getting fuel to the engine. It can also tell you if a fuel pump might be the source of symptoms such as rough idle, hard starting, hesitation, lack of power under load, etc. Installing a fuel pressure gauge, at least a mechanical gauge, does involve finding a source that will be under pressure. To avoid the risk of bringing fuel into the cabin, install an isolator between the gauge and the source. It sounds a little complicated, but kits are available with the parts you need.
Gale Banks Engineering 866-738-5915 www.bankspower.com
Isspro 888-447-7776
Sunpro 800-228-7667 www.sunpro.com
Superchips 888-227-2447 www.superchips.com
BD Engineering carries a broad line of diesel gauges to go with their performance equipment, both analog and digital, including these 2-inch gauges shown here. They also have a monitor for exhaust brake pressure and other diesel performance-specific gauges. Most gauges are available in silver, black and white faces, with mounts to fit your pillar or dash.
Sunpro has factory-calibrated, certified gauges like the Sport ST exhaust gas temp gauge shown here. Sunpro gauges are available separately or as part of a set that includes a universal gauge pod. Note hte very high scale, up to 2,000 degrees F. While sustained temperatures above 1,200 degrees would be destructive, higher temps might be briefly observed such as during particulate trap regeneration. Sunpro Sport ST gauges feature a black dial face and illuminated pointer for easy viewing as well as enhanced night visibility. Factory-calibrated and certified, they come with hardware for installation and are backed by a full one-year warranty. To assist customers, Sunpro maintains a support center staffed by ASE-certified technicians to answer product questions - from proper use and installation to gauge calibration. The support center can be contacted at 800-228-7667, Monday through Friday 8 a.m. to 6 p.m. EST.
For exhaust temperature measurements, Danin has a selection of different thermocouples to meet all needs. Four types of thermocouples have a quarter-inch diameter probe. These are the most popular tpes of thermocouples, but in cases where instantaneous measurements are required, the company also offers two thermocouples with an ultra-sensitive eighth-inch diamater probe. The Danin thermocouples are manufactured in the USA and designed with an inconel tip hat will provide years of trouble-free operation. The manufacturer advises not to bend the thermocouple too severely, and secure the installation so that it does not bounce around when the vehicle is in otion. If a straight tube thermocouple is not suitable, they recommend the use of a thermocouple with a 90 degree bend. The company can also custom-design thermocouples for any special requirements.
There are those diesels that come without tachometers. It's possible to isntall one, but where to pick up a signal is the issue. This Sunpro tachometer adapter is designed to provide RPM signal for aftermarket tachometers on systems such as coil plug and coil pick. According to Sunpro, it also works on most electronic diesel injectors through a pickup clamp that senses current.
It's nice to know what your gauge is going to look like at night, as shown in this photo of a Di/Pricol mechanical gauge with 270 degree sweep for fine resolution and accurate measurement of boost presssure. At Di/Pricol, each gauge is tested and calibrated for accuracy and uses 100 percent LED illumination for crisp, bright details. Custom range gauges can be supplied for special orders. Tubing kits for connecting these gauges to the pressure source are also available.
This nitrous pressure gauge is two and one-sixteenth inches in diameter, and shows a range of 0-100 psi The gauge, part of Autmo Meter's Phantom II line, hasa full sweep needle, Stepper Motor movement and electric power.
Banks carries a full line of Dynafact instrumentation and mounting kits aimed at diesel users who need to monitor conditions based on racing, towing, or heavy-duty use. This particular gauge measures transmission oil temperature, useful to verify proper lubricant warm-up or cool-down to safeguard transmission life. Color-coded face is designed to be read at a glance; comes with 2-year limited warranty.
To keep track of maintenance schedules for work vehicles that do not log a lot of miles, such as tractors and off-highway crawlers, an hourmeter is sometimes helpful. Di/Procal offers several hourmeters to meet a variety of design and voltage needs, all individually tested before leaving the plant. For hourmeter inquiries please contact the company directly at 800-398-6590.
ISSPro, Inc. is a global supplier of electronic instrumentation, sending units and controls for monitoring engine and vehicle systems. This mechanical turbo boost gauge reads up to 60 psi. The white face with red pointer design has numerals that light up green to match 2004 and up Dodges. Pressure tubing, required for installation, is also available.
