High EGT

the blue thing · 08-20-2005, 04:28 AM

Guys:

I took the car to the highway today and I logged a peak EGT of 1660 F at 10.4:1 AFR

. Is this a little too high for the STI? Here is what I have in my car.

94 octane gas
Zeitronix WB o2 with boost sensor and EGT
Helix catless downpipe with thermo coat
Vibrant 3" exhaust
Wolfplayer's rescaled 91 Street Tuner stage 2 map

Can anyone please tell me what is going on with my car? My car has never reached that high of an EGT even when I had the stock downpipe. As far as I remembered, EGT was always around 1400 - 1500 F. I am sure it has nothing to do with Wolf's map as it is only a rescaled version of the original stage 2

daemon · 08-20-2005, 04:40 AM

What were the timing and boost like? Outside temps?

FWIW, I used to hit 1600-1625 with the Cobb AP Stage 2 map during a prolonged high gear pull. I'd be scared if it sat there all the time, but a brief hit now and then shouldn't hurt it.

the blue thing · 08-20-2005, 04:49 AM

boost was at 18.2 psi and outside temp was around 20. Isn't it true that this kind of an EGT indicates a lean running engine? I am confused because the stock ST map is supposed to be super rich

daemon · 08-20-2005, 05:21 AM

It was 18.2 psi at the time you were hitting 1660F? Stock turbo?

Leaning out AFR increases EGTs as does reducing timing. As most likely does running your turbo outside its efficiency range (hot air in == hot air out). That's why I'd say if you are hitting 18.2 psi at redline on the stock VF39, fix that.

I believe low humidity will also raise EGT over high humidity. Never tested, but seems right.

the blue thing · 08-20-2005, 05:34 AM

I didn't have the laptop hook up at that time, but I am pretty sure EGT was hitting 1660 when boost was 18.2. I have a stock turbo and 18.2 psi is around the efficiency limit. I will get up my laptop next time when I do the run

daemon · 08-20-2005, 05:39 AM

At what RPM?

the blue thing · 08-20-2005, 05:42 AM

i would say around 4500 - 5000 rpm

daemon · 08-20-2005, 05:55 AM

OK. A log would be good. The VF39 losses efficiency pretty quickly as flow increases. 18.2 is fine lower in the RPM band, but needs to tapper. I don't claim to know exactly what the efficiency band is for the VF39, but you might try dropping down to about 16 psi at 5000RPM to see if that helps. Your weather is a lot cooler than mine, so that certainly should be in your favor. If you lower boost a tad, you can possibly increase timing a tad. That would lower EGT.

the blue thing · 08-20-2005, 06:05 AM

thanks, I will try that...........but I was searching through NASIOC.com and somebody seemed to have the same problem and that was a faulty factory o2 sensor

daemon · 08-20-2005, 07:19 AM

Does your factory O2 sensor read (roughly) the same as your wide band during closed loop?

the blue thing · 08-20-2005, 07:37 AM

I never thought about that!!! I will check it tonight

the blue thing · 08-25-2005, 05:53 AM

Daemon,

I checked the datalog of the last couple of days and I think I know what caused the high EGT. The Zeitronix display showed a peak of 1720 F today

, and I found that it happens at WOT between the range of 4500 - 6000 rpm. Boost tapers like normal in that range (as a matter of fact, I changed my helix catless to an Ultimate Racing Catted downpipe this weekend just to get ride off the nasty boost creep and smell), but WB o2 shows 11.5 AFR. I will play around with the fuel tonight and hope that it will solve the problem. By the way, how accurate are the EGT sensor in general? I installed it on the #3 cylinder side just before it meets #1 cylinder. Did I do it right? should I install it somewhere else?

daemon · 08-25-2005, 06:04 AM

That's pretty darn hot. I'd be scared. If it only lasts for brief moments, it might be ok. But it would scare me for sure. I'd try to get it down.

BTW, a cat will increase back pressure and raise EGT. So if you tunned for cattless, you might need to take that into account.

I have mine tapped at number 4, a few inches down. I'm not on stock headers, FWIW. I have no idea how consistent readings are between manufacturer's, etc. Mine is a Defi gauge.

the blue thing · 08-25-2005, 06:15 AM

yeah man I am scared!! I am lucky that the engine is still running fine! AFR is around 11.5 and I will make it < 11:1 tonight. I am shock to find that the stock stage 2's fuel map is that lean (maybe something's wrong with the #3 injector and I may send it out for cleaning, it would have been nice if ST supports 4 channels EGT and then I will see how each injector is running). By the way, should I do anything to the ignition??? I heard that ignition should be around 20 around that range

jays05 · 08-25-2005, 06:22 AM

Maybe you are running out of fuel? Post logs please... if you don't have an aftermarket intake on the car and your MAF is in order (try cleaning it with non-chlorinated brake cleaner), your AFR's should be pig rich with the base stage 2 fuel maps.

08-25-2005, 06:22 AM	#15
jays05 Spec C Club Fav Mod: when it's not blown up Location: Upstate NY Posts: 1,541 Join Date: Nov 2004 Trader Rating: (0)	Maybe you are running out of fuel? Post logs please... if you don't have an aftermarket intake on the car and your MAF is in order (try cleaning it with non-chlorinated brake cleaner), your AFR's should be pig rich with the base stage 2 fuel maps. This ad is not endorsed by this member. Please register or login to hide this ad.

08-20-2005, 04:28 AM	#1
the blue thing Amateur STI Driver Car: 04 Subaru WRX STi Fav Mod: Coming Soon Location: Canada Posts: 48 Join Date: Jul 2005 Trader Rating: (0)	High EGT Guys: I took the car to the highway today and I logged a peak EGT of 1660 F at 10.4:1 AFR . Is this a little too high for the STI? Here is what I have in my car. 94 octane gas Zeitronix WB o2 with boost sensor and EGT Helix catless downpipe with thermo coat Vibrant 3" exhaust Wolfplayer's rescaled 91 Street Tuner stage 2 map Can anyone please tell me what is going on with my car? My car has never reached that high of an EGT even when I had the stock downpipe. As far as I remembered, EGT was always around 1400 - 1500 F. I am sure it has nothing to do with Wolf's map as it is only a rescaled version of the original stage 2 This ad is not endorsed by this member. Please register or login to hide this ad.

08-20-2005, 04:40 AM	#2
daemon Professional STI Racer Car: 2004 STi Location: Florida Posts: 806 Join Date: Feb 2004 Trader Rating: (0)	What were the timing and boost like? Outside temps? FWIW, I used to hit 1600-1625 with the Cobb AP Stage 2 map during a prolonged high gear pull. I'd be scared if it sat there all the time, but a brief hit now and then shouldn't hurt it.

08-20-2005, 04:49 AM	#3
the blue thing Amateur STI Driver Car: 04 Subaru WRX STi Fav Mod: Coming Soon Location: Canada Posts: 48 Join Date: Jul 2005 Trader Rating: (0)	boost was at 18.2 psi and outside temp was around 20. Isn't it true that this kind of an EGT indicates a lean running engine? I am confused because the stock ST map is supposed to be super rich

08-20-2005, 05:21 AM	#4
daemon Professional STI Racer Car: 2004 STi Location: Florida Posts: 806 Join Date: Feb 2004 Trader Rating: (0)	It was 18.2 psi at the time you were hitting 1660F? Stock turbo? Leaning out AFR increases EGTs as does reducing timing. As most likely does running your turbo outside its efficiency range (hot air in == hot air out). That's why I'd say if you are hitting 18.2 psi at redline on the stock VF39, fix that. I believe low humidity will also raise EGT over high humidity. Never tested, but seems right.

08-20-2005, 05:34 AM	#5
the blue thing Amateur STI Driver Car: 04 Subaru WRX STi Fav Mod: Coming Soon Location: Canada Posts: 48 Join Date: Jul 2005 Trader Rating: (0)	I didn't have the laptop hook up at that time, but I am pretty sure EGT was hitting 1660 when boost was 18.2. I have a stock turbo and 18.2 psi is around the efficiency limit. I will get up my laptop next time when I do the run

08-20-2005, 05:39 AM	#6
daemon Professional STI Racer Car: 2004 STi Location: Florida Posts: 806 Join Date: Feb 2004 Trader Rating: (0)	At what RPM?

08-20-2005, 05:42 AM	#7
the blue thing Amateur STI Driver Car: 04 Subaru WRX STi Fav Mod: Coming Soon Location: Canada Posts: 48 Join Date: Jul 2005 Trader Rating: (0)	i would say around 4500 - 5000 rpm

08-20-2005, 05:55 AM	#8
daemon Professional STI Racer Car: 2004 STi Location: Florida Posts: 806 Join Date: Feb 2004 Trader Rating: (0)	OK. A log would be good. The VF39 losses efficiency pretty quickly as flow increases. 18.2 is fine lower in the RPM band, but needs to tapper. I don't claim to know exactly what the efficiency band is for the VF39, but you might try dropping down to about 16 psi at 5000RPM to see if that helps. Your weather is a lot cooler than mine, so that certainly should be in your favor. If you lower boost a tad, you can possibly increase timing a tad. That would lower EGT.

08-20-2005, 06:05 AM	#9
the blue thing Amateur STI Driver Car: 04 Subaru WRX STi Fav Mod: Coming Soon Location: Canada Posts: 48 Join Date: Jul 2005 Trader Rating: (0)	thanks, I will try that...........but I was searching through NASIOC.com and somebody seemed to have the same problem and that was a faulty factory o2 sensor

08-20-2005, 07:19 AM	#10
daemon Professional STI Racer Car: 2004 STi Location: Florida Posts: 806 Join Date: Feb 2004 Trader Rating: (0)	Does your factory O2 sensor read (roughly) the same as your wide band during closed loop?

08-20-2005, 07:37 AM	#11
the blue thing Amateur STI Driver Car: 04 Subaru WRX STi Fav Mod: Coming Soon Location: Canada Posts: 48 Join Date: Jul 2005 Trader Rating: (0)	I never thought about that!!! I will check it tonight

08-25-2005, 05:53 AM	#12
the blue thing Amateur STI Driver Car: 04 Subaru WRX STi Fav Mod: Coming Soon Location: Canada Posts: 48 Join Date: Jul 2005 Trader Rating: (0)	Daemon, I checked the datalog of the last couple of days and I think I know what caused the high EGT. The Zeitronix display showed a peak of 1720 F today , and I found that it happens at WOT between the range of 4500 - 6000 rpm. Boost tapers like normal in that range (as a matter of fact, I changed my helix catless to an Ultimate Racing Catted downpipe this weekend just to get ride off the nasty boost creep and smell), but WB o2 shows 11.5 AFR. I will play around with the fuel tonight and hope that it will solve the problem. By the way, how accurate are the EGT sensor in general? I installed it on the #3 cylinder side just before it meets #1 cylinder. Did I do it right? should I install it somewhere else?

08-25-2005, 06:04 AM	#13
daemon Professional STI Racer Car: 2004 STi Location: Florida Posts: 806 Join Date: Feb 2004 Trader Rating: (0)	That's pretty darn hot. I'd be scared. If it only lasts for brief moments, it might be ok. But it would scare me for sure. I'd try to get it down. BTW, a cat will increase back pressure and raise EGT. So if you tunned for cattless, you might need to take that into account. I have mine tapped at number 4, a few inches down. I'm not on stock headers, FWIW. I have no idea how consistent readings are between manufacturer's, etc. Mine is a Defi gauge.

08-25-2005, 06:15 AM	#14
the blue thing Amateur STI Driver Car: 04 Subaru WRX STi Fav Mod: Coming Soon Location: Canada Posts: 48 Join Date: Jul 2005 Trader Rating: (0)	yeah man I am scared!! I am lucky that the engine is still running fine! AFR is around 11.5 and I will make it < 11:1 tonight. I am shock to find that the stock stage 2's fuel map is that lean (maybe something's wrong with the #3 injector and I may send it out for cleaning, it would have been nice if ST supports 4 channels EGT and then I will see how each injector is running). By the way, should I do anything to the ignition??? I heard that ignition should be around 20 around that range