Understanding the basics Of EGTs means knowing what’s a high number, and how hot is too hot. One of the most basic measures of how a diesel engine is performing can be measured in exhaust gas temperature or EGT for short. Whether you’re on the street towing a trailer or at the track making a pass, having a way to monitor EGTs is an important indicator of whether your engine is going to be in trouble or not.
Measuring EGTs is not rocket science. To accomplish this, a probe (pyrometer) is inserted into the exhaust system. In the past, pyrometers were positioned in the exhaust stream after the turbo, mainly because if things got too hot and there was a failure with the probe, it wouldn’t go through the turbo. With new probes being constructed of better materials, however, failure is nearly unheard of, and it is safe to mount most probes right in the exhaust manifold, where the exhaust temperature is the hottest. This ensures a good reading of whether the turbo is in danger of failing or not. Turbochargers are tough, but give them enough pressure and exhaust heat, and even the toughest turbo can fail.
In the past, EGT probes have been inserted post-turbo to avoid issues, but with new technology and materials, virtually all temperature probes are now installed in the manifold to accurately measure EGTs.
Deciding whether to mount the pyrometer thermocouple (probe) before or after the turbine is usually a matter of utilizing a suitable mounting location. However, if you do mount your probe after the turbo, the temperature at full throttle or when under load can be 200 to 300 degrees lower than if the EGTs were measured in the exhaust manifold. This temperature difference is why the installation of the thermocouple in the exhaust manifold is considered more accurate.
If EGTs Are Important, Why No Gauges From The Factory?
One frequently asked question concerns the OEMs and exhaust gas temperature. Many want to know why trucks do not come with EGT gauges from the factory. The answer here is somewhat comical, but also somewhat obvious. Most companies figured that consumers wouldn’t understand the gauge or what it means. Some might treat it like a tachometer and try to wind it out, other consumers might view it like a temperature gauge, and get nervous at anything over half readings. Since most all trucks have pre-programmed limits for maximum exhaust gas temperatures, the Big Three consider an EGT gauge unnecessary.
Either traditional analog style or…
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