mikjel

I will be installing a guru chip, map-kit, 55 injectors ++ in my car this week.

Because of that (and for the fun) I have installed a plx wideband O2 and a autometer boostgauge and -pyrometer (cyl. 4, about 3" from the cylinderhead).


Yesterday I was out testing the readings on my stock 88 951S (only modification: no cat).

Air Fuel Ratio:
WOT, rpm steady (brakeboosting)

2000=12,6 (3 psi)
2500=12,6 (9 psi)
3000=12,6 (12 psi)
3500=12,2 (12 psi)
4000=12,0 (12 psi)
4500=11,3 (12 psi)
5000=11,3 (11 psi)
5500=12,2 (11 psi)
6000=12,5 (10 psi)
6300=12,8 (10 psi)

I guess this is ok, but the leaning out at high rpm is maybe not very ideal?


But I was surprised to see the high egt-numbers:

Steady 4000 rpm (no boost) = 1480F
Steady 4000 rpm WOT = 1480F
Steady 5000 rpm (no boost) = 1580F
Steady 5000 rpm WOT = 1530F
Steady 5500 rpm (no boost) = over 1600F
WOT over 5500 = over 1600F

These tests was done in 3. and 4. gear. Outside temerature 0 celsius (freezingpoint)

I thought we were supposed to keep the egt under 1550F on our cars, but I don't understand how that is possible on a tuned car when my stock car have these high numbers on a very cold day.
Or is my new pyrometer wrong?

jimbo1111

I would trust the EGT over the WB. Unless you varify the WB with a dyno's WB.

turbo944

If you are sitting still and brake boosting, you are probably going to see higher temps, IMHO......if you can't do datalogging, get a rider on board to watch and see. With no airflow blasting through the engine compartment, you will end up with higher temps as little of the normally natural cooling is going on. If you are driving and stabbing the brakes while you boost, you're putting additional load on the engine then as well and holding it, which would also tend to make it work harder than it would normally.

I would think those AFR readings are pretty good if the sensor is good and the unit is as well. 12.8 is just above the 12.5 that is supposed to give about the best ratio for power and a bit of extra fuel for cooling. If you started getting up into the 13s, then I would start to be concerned. The 11s you saw are actually probably too rich and robbing you of a bit of midrange power.

adrial

Where is your EGT sensor located? Where is your wideband O2 sensor located?

MySwiss

Mikjel. I have concluded the same thing with my new car, which came equiped with an Autometer EGT gauge. It easily reaches 1600 degrees or more at WOT and crusing at 3500rpm to 4000rpm will generate 1400 degrees or so.

If you have a way of adjusting your fuel, keep it a little more rich above 5500rpm. You won't see a difference in power (I have dyno sheets to prove it) and you will bring down your EGT some what. If you can also add a bit of timing on the top end ( if your using some decent octane), that will also help.

Last but not least, an Aquamist system will really help bring down those EGT's.

Bengt Sweden

Hi Mikjel,
1600F or below 900C shouldn't be a problem.
With Guru chip you will get better A/F = leaner below 3500rpm.
You will probably also get lower EGT since ignition is more advanced. You can run an aggressive setting if you use premium fuel.

Unfortunately water injection will actually raise EGT due to slower combustion.

Cruising should not give temperatures as high as 1400F.

Sorry for the mixed answers you get.

Bengt

Gary Gaukler

Just one more data point, for what it's worth:

My car also shows EGT 1450 when cruising at 3000-4000rpm. O2 shows stoichiometric mixture (i.e., sweeping). Location of EGT is same as mikjel's, 3" from head on #4 runner.

If I floor it in 5th and boost builds to 12psi, EGT stays at 1450 (until 4000-4200rpm, haven't gone higher on public roads).

Gary.

adrial

Slight hijack, but could any of you that have EGT sensors mounted in the manifold send me a picture? I need to place my bungs for the EGT sensors...

Thanks!

akboost951@hotmail.com

Chas

Can you place an EGT sensor IN the stock o2 location (In the crossover)? I have a WBO2 sensor in my downpipe, and as soon as I use that to feed the computer a signal, I'm taking out my old o2 sensor and hopefully put in an EGT sensor...good idea?

toddk911

I also have an EGT getting ready to be installed abd would like to see pic of mounting.

MySwiss

Guys. Egt sensor should be in the Exhaust manifold. you will need to tap in it and thread your sensor in it. It is best to do this when the headers are out, so shavings don't get in the turbo. #4 is an easy fit. I don't have my camera (repair), so I can't supply any pics, but it's pretty straight foward.

NZ951

egauges a good supplier for an EGT?

Gary Gaukler

I'd love to, but you can't see the EGT probe at all in my install. It's sort of pointed downwards on #4, and all you really see is the sensor wire going over to the firewall...

Gary Gaukler

No, that's not a good idea. The EGT sensor should be as close to the combustion chamber as possible. After all, that's what you are interested in - chamber temp. Placing it in the downpipe or other places far away would get you pretty meaningless numbers.

Gary.

NZ951

Ok, so I am getting one of these, is 3 gauges and a shift light in a pillar too much? Have a boost/vac and link a/f gauge currently... Where to put my knock gauge then? Damn, I need one of those replacement dash kits...