Trying to find some general info regarding EGT temps. I recently installed a sensor on each bank within a couple of inches of the end of the truck header which works out about 4-5" from #1 and #2 exhaust ports.

I've been watching them for a couple of weeks in datalogs to have an idea of where they seem to run. For cruising I've messed with the timing to see what the effects are on coolant temps. I've been tuning traction control via cutting timing and I've seen the EGT's climb from 1500ish to 1800 in less than 1.5 seconds when the timing gets cut down to 3-5 degrees to stop the wheel spin. It seems for cruising they run in the 1150-1350 range. It would seem that for cruising the lower the EGT's the better, so I've been trying to tune for lower EGT readings when cruising.

My first real question is how hot is too hot and where should I be when trying to make maximum power? And can timing cuts for launching or traction control that increase the temps hurt for periods less than a 2 seconds without much engine load?


The car is a mostly street build Motown LS with an S480, meth injection, truck manifolds on a set of 317's. Only estimates on power - at 70%DC on a set 80lb Siemens at 62-64 lbs of fuel pressure and 15-16 lbs of boost just below 12:1 AFR. It still has a lot more in it, just creeping up on it. I've been warned to not get crazy chasing EGT numbers, so I've been using them as more of a guide to what's going on in different conditions/situations.

I posted this on another forum without alot of response other than to run some form of alcohol, which I'm not going to do anytime soon. Thanks in advance for any insight.

 

with egt there is a lot of "depends", really close to the head and they read the flame temp which most want, too far away gives a much cooler reading, what type of element its it an open couple give the fastest and accurate but life is short.

the only 2 definates in egt tuning is that when adjusting fuel the stoich mixture is the hottest and gets colder either richer or leaner than that and more timeing cools off as well.

so for tuning cruising fuel i would tune it till it is hottest. for your 12:1 afr at 15 lbs of boost, i would never do that on pump gas, if longevity takes precidence over a few horspower i would run high 10's low 11's to keep a safety margin.

depending on egt placement anything over 1700 while making power is danger zone to oe valves and pistons.

 

The sensors are 'closed' element type sensors. And what you're describing is making me feel better. The temps will only exceed low 1700's when the timing gets cut for traction control at full load.

In term of 12:1, I'm just under that presently between 11.6-11.8. I have to admut that the difference between 11 and high 11's is minor to say the least. At 10:1 AFR I can feel that it's too rich without looking at the gauge or datalog.

I intend to put some more meth to it in the very near future. I've been running a 625mi/min nozzle and I'm going to add another. How much of an effect on EGT's will there be with more meth? I'd assume there will be an effect, but will it be negligible?

And thanks for the response!

 

I took this advice and I appreciate some sensibility. You're 100% spot on. There is no need to push this into the mid to high 12's.

FWIW, I put on the drag radials and am still tuning, but they help a TON in terms of keeping the wheel spin and traction control timing retard to a minimum. I made a couple of pulls today for more than 4 seconds and the EGT's are in the 1600 range. Trying to stop all of the wheel spin with timing retard on an 800+HP car with a street tire is silly. Obviously negative timing is going to create a crap ton of heat in the exhaust manifold.

Thanks again ashford!

 

I have some experience with egt tuning, but on 2 strokes. Like Ashford posted, egt's can be all over the place, and definitely lead you in the wrong direction. Most tell you the plugs are the end all, (at least on the 2 strokes, but makes sense on 4 as well), and egt's work best for monitoring cyl to cyl tuning. I've personally lost cyl's at 1200*, and had great looking plugs, and fuel wash at 1450* both on race gas.