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Watchful Eye: Why Your Diesel Needs Aftermarket Gauges

Whether you’ve noticed them strung along the A-pillar, mounted on the dash, attached to the steering wheel, or digitally displayed on the screen of a monitor, gauges are the most indispensable way of protecting your diesel investment. Thanks to large displacement engines turning out gobs of low-end torque and beefy chassis enabling gargantuan towing capacities, modern diesel pickups are impressive machines—but they have their limits. While any late-model oil-burner can tow 20,000 pounds with relative ease, they can also generate tremendous heat in a hurry. To keep tabs on the condition of the engine, transmission, fuel system and other key powertrain vitals in real time, tens of thousands of diesel owners have turned to aftermarket gauges in one form or another.

Depending on whether you’re using your truck to tow, daily drive or race, your gauge needs will vary. However, due to the versatile nature of diesel trucks, many owners dabble in all three of the latter categories at some point. As a general rule of thumb for performance, towing and street-driven applications, a pyrometer should be installed to measure exhaust gas temperature (EGT), a transmission temp gauge should be employed to make sure the automatic transmission doesn’t see excessive heat and a boost gauge is often utilized to see how hard the turbocharger is working. Before you bury the needle, get these vital gauges installed on your diesel, and then think about adding a few more for ultimate powertrain protection.

EGT Is Your Enemy: Get a Pyrometer ASAP


If you tow often you’ll want to make monitoring exhaust gas temps your highest priority. Although there is no definitive temperature that keeps you in the safe zone, the most commonly adhered to safety threshold for maximum sustained EGT is 1,250 degrees F. Going beyond that should only be done in short intervals, such as allowing EGT to creep up to 1,300 or 1,400 degrees while climbing a grade. Expect to see 300 to 400 degrees at idle, 700 to 800 degrees cruising empty and anywhere from 900 to 1,300 degrees (depending on your truck’s level of modification, the load it’s hauling or the terrain you’re covering) when cresting a hill with a trailer in tow.

Meltdowns Can Be Avoided


Exposing a diesel to high EGT for miles on end can have catastrophic consequences. Over the years, we’ve seen melted pistons, cracked heads and damaged turbine wheels all result from extreme EGT. The unfortunate part is that the failures could’ve been avoided if the owner had had a means of monitoring his or her exhaust gas temps. If we could only add one gauge to our truck, it would be a pyrometer.

Safeguarding Your Slushbox


It’s a fact that the biggest killer of automatic transmissions is excessive heat, so while a pyrometer should be priority number one for trucks that tow, transmission temperature monitoring should be a close second. For performance-oriented or race-ready diesels, running a transmission temperature gauge is of utmost importance. In racing applications, most transmission heat is generated on the starting line while trying to build boost (i.e. being up against the converter) and during shifts (when some slippage occurs). In towing situations, extreme heat can be generated in lower transmission gears (before converter lockup occurs), at low vehicle speeds with the converter unlocked and/or as you climb a steep grade.

100 Degrees Above Ambient


Don’t be alarmed to find the needle in your transmission temperature gauge creeping toward the 200 degree mark on a 95 or 100 degree day. The unwritten rule of normal transmission operation is that it’s acceptable for them to run 100 degrees over ambient air temperature. Between the 210 to 220 degree mark, we would make monitoring transmission temperature our top priority. Beyond 220 degrees, we would find a place to pull over and let things cool off.

Coolant Temp: Don’t Forget About It


If you tow a lot, you’ll likely spend most of your time watching your exhaust gas temps via the pyrometer. However, it’s vitally important that you also keep tabs on coolant temperature, especially when ascending a hill. Remember, diesels can lug almost any load up a grade without downshifting. This means low engine speeds are maintained even though the engine is under considerable load. Even though EGT may be manageable, coolant temps can skyrocket under such conditions.

EOT and ECT: Important for All (But None More Than for the 6.0L)


While engine oil temperature (EOT) should never be ignored, in 6.0L Power Stroke applications it should always be displayed on any monitor or gauge you’re using, along with coolant temp (ECT). This is because the coolant side of the engine’s oil cooler is prone to clogging, blocking coolant flow and super-heating the engine oil. A difference of 10 to 15 degrees or more between the two parameters indicates that this is happening. Products such as the Edge Insight CTS2 and SCT Livewire TS+ have proven invaluable to 6.0L owners, who—thanks to consistently monitoring the delta between EOT and ECT—have been able to detect the early warning signs of an oil cooler failure. (Note that once the oil cooler is completely plugged it often leads to catastrophic EGR cooler failure as well).

Boost Gauges: Popular but Not Paramount


Although it’s never a bad idea to make sure your turbocharger isn’t building an inordinate amount of boost pressure, a boost gauge makes the most sense in a race or competition application. However, on a street-driven truck or a tow mule, a boost gauge can also help determine why your turbo isn’t making the kind of boost it should. In performance instances, a drive pressure gauge is even more useful, as drive pressure is almost always higher than boost pressure in any given driving condition and extreme drive pressure is responsible for most turbocharger failures. Still, a boost gauge is something most diesel owners add at the same time they install their pyrometer and trans temp gauges. Likewise, on digital monitors boost is one of the first parameters diesel owners want to have on display.

Low-Pressure Fuel Supply


Fuel supply is the lifeblood of any diesel engine, but not only does a lack of adequate supply lead to dismal performance, it can also be harmful to injection system components (namely injection pumps and injectors). A fuel pressure gauge can tip you off as to whether or not your lift pump is on its way out or is no longer able to keep up with low-pressure fuel demand. Because fuel system components on diesel engines are far from cheap, this is one of the first gauges we would install or add to our digital monitor’s list of viewable parameters.

Injection Pressure Is Everything


A drop in fuel rail pressure (or high-pressure oil pressure on 7.3L and 6.0L Power Strokes) due to an injector up-size or aggressive tuning is a surefire way to experience power loss, increased fuel consumption and excessive smoke out the tailpipe. Just like a fuel supply pressure gauge, monitoring rail pressure can help you diagnose a potential problem before damage is inflicted on any injection system components.

All-In-One Gauge


As far as parameter monitoring is concerned, the Insight CTS2 monitor (and the CTS that preceded it) from Edge Products has all but taken over the world. With this bad boy, you can keep tabs on virtually everything your truck’s ECM does, along with using it to read and clear diagnostic trouble codes (DTCs), log data and even warn you when a certain parameter exceeds its pre-set limit. The high resolution, color touch screen provides for both convenient monitoring and configuring of the CTS2, and the fact that you can watch as many as 12 parameters at a time has made it the preferred monitoring device in the diesel segment.

The Perfect Addition


Some truck owners even use a CTS2 to combine forces with their existing A-pillar gauges, and (as if the CTS2 needed another selling point) on top of monitoring everything the truck’s computer does, additional parameters can be monitored by installing the optional Edge accessory system (EAS). This system allows you to view up to 16 additional parameters on your CTS2 by way of installing universal input sensors (0-5 volt).

Innovation Along the A-Pillar


As proof that versatility can be had in a compact package, the FD series Interceptor scan gauge from Aeroforce Technology fits standard 2-1/16-inch gauge pods, allows you to monitor two parameters at a time and—like the Edge Insight CTS2—can essentially display any powertrain vital the truck’s computer can. Thanks to its ability to monitor commanded injection control pressure (ICP, i.e. high-pressure oil pressure), injection pressure regulator (IPR) duty cycle and perform both buzz tests and cylinder contribution tests on the 7.3L Power Stroke, many ’94.5-’03 Ford owners run this compact yet comprehensive gauge (yours truly included).

It Only Makes Sense…


In a world now controlled by smartphones, they too can serve as a means of monitoring your truck’s powertrain vitals. Why not? We already use them for everything else. Thanks to the products offered by companies like EZ Lynk and SCT (the Auto Agent and iTSX, respectively) you can also tune your truck’s ECM using your phone. You simply plug the pass-through device that provides a Wi-Fi access point into the OBD-II port, download the app, turn your Bluetooth setting on and you’re on your way. As far as ’08-newer Fords, ’11-‘17 GMs and ’10-present Rams are concerned, EZ Lynk in particular has become one of the most popular methods of tuning a late-model Power Stroke, Duramax or Cummins diesel.

Key Parameters to Monitor While Towing:

  • Exhaust Gas Temp (EGT)
  • Transmission Temp (TFT)
  • Engine Coolant Temp (ECT)
  • Engine Oil Temp (EOT)

Key Parameters to Monitor While Racing:

  • Transmission Temp (TFT)
  • Fuel supply pressure
  • Fuel Rail Pressure (FRP) or High-Pressure Oil Pressure
  • Boost pressure
  • Drive pressure
  • Exhaust Gas Temp (EGT)
  • Engine Coolant Temp (ECT)

Data logging is your best friend when trying to keep an eye on all of the parameters listed above.

Want to know how to fix some of the OEM problems with your diesel truck? We have 5 fixes, and 5 more fixes, you should do!


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