http://www.sdsefi.com/techegt.htm
Most engines will make maximum power at an AFR of between 12.0 and 13.5 to 1 however, the EGT may vary from 1250F to 1800F and is dependent on many factors.
Uh, you might find that you can increase boost and hp quite a bit if you are willing to bring the timing back a little bit..
OK, here is ALL that egt is good for.
AF= rich, EGTs go down
AF= max hp, EGTs fairly high
AF=stoich (optimum burn), EGTs highest
AF= lean, EGTs go down again
Here is what you want to do:
NOTE: DO NOT CHANGE TIMING ANYWHERE DURING THIS PROCEDURE OR YOU WILL HAVE TO RESTART THE WHOLE TUNING SEQUENCE
Go to a dyno or a decent stretch of road
Set your starting AF to something around 12.5 or so, or as rich as possible while able to keep the car running.. 12 is about the most rich you can have a car and have it still run, but, the danger with 12:1 AF is that it can cause scoring on the cylinder bore by diluting the oil with excess fuel; you have been warned.
Note the EGT temp: REMEMBER, THIS IS YOUR EGT, FOR YOUR CAR, not for everyone elses: it may be HIGHER than joe blows, it may be LOWER, but its YOURS and thats all that matters.. The actual NUMBER is not the issue, its HOW THIS NUMBER CHANGES AS YOU TUNE THAT MATTERS!!!
lean the car out a bit, maybe half a point on the ratio, do a run, and make sure the EGT increases slightly; if it does, this is a verification that you are truly both on the rich side AND your 02 is reasonably accurate. If all is well, you should notice an increase in hp from the last adjustment. This is a good sign.
drive, and notice the response and activity of the motor and watch for low rpm knocking, bucking, etc
lean it another quarter ratio, watch the egt go up again
once again watch for any symptoms of problems
Anyway, you keep doing this until you reach an EGT that you feel is a little too hot or until you reach a point whereby your motor was running very good, but the last enleanment had it starting to act up or you feel the hp decrease. Once you are at that point, increase the fueling by around a quarter or half point AF and drive for a while there. That should end up being a decent and fairly safe tune.
If you are knocking and can't even get to around 12.5 without the car running badly, retard the timing and start the tuning sequence over.
Essentially, the EGT is going to tell you when you are at max. hp, which is slightly over stoich WITHOUT knock or scary EGT temps.
An EGT is VERY helpful if you are using a narrow band O2, since they aren't known for accuracy and the EGT is a good reality check.
An EGT is also a good reality check for WBO2s, since they have often shown to be innacurate as an absolute reference, but still good as far as telling you whats happening. The EGT gives you an idea of exactly WHAT the WBO2 is showing since the EGT will max out at EXACTLY stoich, whereas the wbo2 might read some crazy thing like 13.5 at true stoich, but there is no fooling the EGT temp curve.
At detonation, what will usually happen is your EGT will dive suddenly and your O2 sensor will read very lean.
IIRC if you are misfiring though, you will get the same thing. EGT goes down because of no burn, and all the unbonded oxygen will tell the 02 sensor that there wasn't enough gas during the burn to bond with the oxygen ie lean.
