Installation and Tuning With an EGT meter
An EGT meter can be a valuable tuning tool if you know how to use it. This article will lead you through an installation and basic tuning information using the EGT meter available from us. The installation is performed on a twin turbocharged V8 engine in a 1991 Ford Mustang.
Tools needed:
1/8" NPT tap
21/64 drill bit
basic hand tools
Instructions:
-Drill a hole one of the primary header tubes. The probe should be
located within 3 inches of the exhaust port if possible.
-Tap the hole with the NPT tap and thread the stainless steel compression fitting into the tube. The metal in headers isn't very thick, so be careful about stripping the threads.
-Insert the probe so that the tip is about 1/4" - 1/2" inside the tube. The tip is where the temperature is read from, so it is important to have it in the exhaust stream. Tighten the compression nut down to secure the probe once it is positioned properly.
-I performed the drilling and tapping with the turbos and manifolds on the car. My feeling was that any steel shavings would be so small that they should get blown out of through the turbine wheel without hurting anything if the car was allowed to idle for a little while. I have had my turbos off since this modification, and they appear to be in perfect shape. My turbos are cheap though. If you have an expensive turbo, use your own discretion here. I might be inclined to remove the turbo and or manifold and make sure everything is clean before re-assembling and running the engine.
-Run the wires inside the car to the meter and plug it in. That's all there is to it.
The 78deg. temperature is because the engine isn't running.I typically
strap the meter to the parking brake handle during a race, and look
at the max temp when I am done.
Tuning
The best way to tune a car is by monitoring the Air/Fuel ratio on a dyno using an expensive wideband AF ratio meter. Once you have established a steady AF ratio for maximum power you take note of the EGT readings at that tune. This will allow you to watch the EGT meter when you are at the track or on the street and make sure that the tune stays approximately the same. I use the peak hold function at the track to record the peak EGT for a pass. If the temperature gets too high, I know I am running leaner than I want to, and I make adjustments to make sure that I am getting enough fuel to the motor for my power level. Or I can back down the boost if I think I have reached the limits of my fuel system. Less boost requires less fuel.
Exhaust gas temperature works like this. Peak EGT will be seen when the engine is burning a perfect stoichiometric Air to Fuel ratio. This occurs at about 14.7:1 on gasoline engines. Best engine performance at WOT is typically seen at A/F ratios between 11.5 and 13. Exhaust gas temperature will be considerably cooler at these mixtures. Retarding timing without making other changes will raise EGT. If AF ratios of greater than 15:1 are reached EGT will begin to drop. So it is VERY important to know which side of peak EGT you are on. It is safe to say that peak power will occur at an EGT somewhat colder than peak EGT. On piston engines EGT readings of 1300-1500 are common at the max power mixture.
On the twin turbocharged shop car, maximum EGT readings of 1400 -1410 are typically seen during a 1/4 mile pass. On the same tune, wideband O2 sensor measurements have shown AF ratios of about 11:1 at WOT. This is on the rich side, even for a turbocharged motor. Some tuning work with the fuel maps using the TwEECer tuning module is going to happen soon to see if a bit more power can be made. Comparing notes with several other turbo v8 cars has shown that EGTs above 1550 are cause for concern. At the very least, wideband monitoring should be performed on a dyno to see if the engine is at a desirable AF ratio. I like to tune for max power on the dyno, then richen the mixture a little bit to make sure I am on the rich side for safety.
Are EGT gauges better than AFR meters? Conventional narrow band oxygen sensors and digital LED meters are not the best devices to measure AFR in the richer ranges but they certainly warn of a too lean condition immediately and obviously, without translation by the driver and they are affordable. Meters combined with wide band sensors are laboratory quality usually, highly accurate and useful but very expensive and sometimes bulky. EGT gauges have the limitations above and are generally priced reasonably. I would suggest that the two types are complimentary. EGT gauges have the advantage of working long term with leaded fuel, which will clog oxygen sensors. EGT gauges are widely used to set mixture on engines used for steady state high power applications where operation has been carefully documented such as in aircraft. The choice would depend on the application. Both are better if you can afford them.
-more info about using EGT to tune can be found at:
http://www.sdsefi.com/techegt.htm