A/F vs EGT.

[contraption22]

Yesterday at Cecil was a good learning experience. Actually my first time in trying to tune with a wideband.

Here is the trouble I had... A/F at WOT was always pretty rich... always richer than 10:1. In fact, my final run at 22psi I was showing 9.49:1 A/F thru the traps. Yet my EGT was hot... 1550+! Puzzled by this, I was reluctant to take out some fuel pressure to lean out the car, afraid of catasrophe with the new engine. My brother's 2.4 Neon was seeing simiar readings, with a rich A/F and a hot EGT. His last pass would have been a good one, but he lifted when he saw the EGT's crest 1600.

So when I got home last night, I started to do some research. Found this on Hahn's website. Incidentally, Bill Hahn's the one that developed the PortFueler system that Joe is using on his Neon.

http://www.hahnracecraft.com/auto/tech/info.htm

To paraphrase, he basically says that an overly rich condition could cause hotter EGT's, with fuel burining in the exhaust manifold.

Any input guys? Thanks in advance

[shadow88]

Your problem seems like you've already covered it here.

http://www.turbo-mopar.com/forums/showthread.php?t=8561

[Dave]

Fuel has a cooling effect on the combustion. If fuel is in the manifold it would cool the charge down, causing lower EGTs. As Frank put it in that thread, your base timing could be off. What's it set to?

[Frank]

Fuel has a cooling effect on the combustion. If fuel is in the manifold it would cool the charge down, causing lower EGTs. As Frank put it in that thread, your base timing could be off. What's it set to?

umm... yes and no. its all dependent on the setup. did you know that you can lean out a car so much that it actual starts runnign cool again?

base timing is out of question... i know mike. plus base timing wouldnt make that much of a difference. computer timing could.

Yesterday at Cecil was a good learning experience. Actually my first time in trying to tune with a wideband.

Here is the trouble I had... A/F at WOT was always pretty rich... always richer than 10:1. In fact, my final run at 22psi I was showing 9.49:1 A/F thru the traps. Yet my EGT was hot... 1550+! Puzzled by this, I was reluctant to take out some fuel pressure to lean out the car, afraid of catasrophe with the new engine. My brother's 2.4 Neon was seeing simiar readings, with a rich A/F and a hot EGT. His last pass would have been a good one, but he lifted when he saw the EGT's crest 1600.

So when I got home last night, I started to do some research. Found this on Hahn's website. Incidentally, Bill Hahn's the one that developed the PortFueler system that Joe is using on his Neon.

http://www.hahnracecraft.com/auto/tech/info.htm

To paraphrase, he basically says that an overly rich condition could cause hotter EGT's, with fuel burining in the exhaust manifold.

Any input guys? Thanks in advance

That is a great article. I dont know your brother's setup, however you are now in uncharted waters because of the cam. I know that making too rich can cause an afterburn effect, however it is also dependent on where the probe is at. That cam may require more timing. Who knows. I personally would definently back the fuel down to the 11.5:1 ratio and see what happens. Then mess with timing. You could be experiencing the result of both.


Personally I am dang impressed! Steve told me about your runs and if you were that rich, then wow, that thing is out of control with that new cam and Super50!!!!