Matt H

Anyone know what the EGt readings should look like? Was lucky enough to pick up a lightly used Greddy EGt gauge for when the car is back together. It reads in deg C and I started thinking, wonder what the EGT is supposed to look like on this car?
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Matt H

One more question if no one has an answer:

Where did you put the bung for your sensor?
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m42racer

The closer to the port the higher the reading will be, and more typical of the combustion chamber temps. I would expect to see numbers range somewhere between 1400 and 1800 F depending upon upper boost values. Remember, these EGT numbers need to be a reference number against some other intake related data, A/F or similar. EGT's without prior knowledge of intake fueling is very dangerous. Make sure you look at your plugs, have a Lambda or someother reference to back up the validity of the EGT numbers. Some engines may see 1400 F port temps and be just fine with a A/F of 12-13 to 1. You may see 1400F and be close to melt down.

rage2

I try not to go above 1550F on the 951 motor. Light peaks to a little over 1600F for about 500rpm, but settles down to 1550F to redline.

I've ran much higher before (1900F) to push another 50hp on pump gas and my exhaust valves weren't too happy.

Matt H

m42 and rage, where do you recommend it be plumbed? In one of the header pipes?
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rage2

Yes, the closer to the exhaust ports the better.

Mike S

I was scared to weld mine to the header so I installed it about 12" in front of the cat. I get temps from around 1200F to 1550F. If you're seeing above 1600F then you are probably have an air/fuel ratio issue.

TonyG

After burning an exhaust valve racing a bunch of 993TT's/996TT's, and new lambos, etc... I limit my EGT to 1550F - 1575F. No more than that.

At that range of EGT, I'm at about 11.0:1 - 11:3:1 a/f ratio.

TonyG

mochman

matt h placement is 1" from the exhaust port #4 cylinder. Tony G gave me the placement and the temps he won't steer you wrong.

Matt H

mochman, got a pic? Who did it for you and how? Just have an exhaust shop cut a hole and weld the bung?
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mochman

no pics got a digital though, I think I need a program though. I did mine when I had the header out and then I tig'd it in. As far as it being installed I heard of guys drilling it at slow speed with a vac. next to it, guys just drilling it, putting grease in the flutes of the bit to catch the metal, the important part is not getting metal through the exhaust to the turbo. Big pieces would be bad, little ones prolly won't bother it. Then weld it in.

rage2

Good to see we're at about the same numbers from trial and error .
I run a 12:1 a/f ratio, with timing in the 20 degree range under boost. I find running less boost, leaner A/F and a bit more timing you'll make pretty much the same power as more boost, richer a/f and less timing. The advantage is fuel economy at the track.

tazman

Would it be ok to weld a bung on a header that has gotten a jet hot type coating on it? Where do you weld it on, the side or top?

mochman

top is best imo, you're gonna destroy the coating around the weld area in and outside the pipe I don't think it would cause a prob. in just a small area, check with whoever did the coating.

Oddjob

I rode with a guy on the track that was running around 15-16 psi boost. He had been playing with his A/F mixture and told me to let him know if I saw his EGT gage go over 1500 deg F.

He had his sender/probe in the number 4 exhaust runner about 1 ½ to 2 inches down from the head port. The word is that the number 4 cylinder is the one that is prone to run the hottest; head gasket failures are more common around #4. Ive burned a #4 exhaust valve and have seen lifting of the #4 fire ring on 2 of the 3 head gaskets Ive had off my engines, so that backs up what I have been told and probably justifies monitoring the EGT on that cylinder.

The other option would be to use the fitting in the crossover pipe for the CO2 test tube. Its probably about 8-12 inches (pipe length) from the crossover/exh manifold flange. I don’t know how much the temps will drop in the distance from the port to that fitting, so it would require some testing, but at least it would not require drilling and welding on the exhaust manifold pipes. Anyone done this or advise against it? Too much variation in the temp drop to be accurate/useful?