FMIC/EGT's question

[starr]

i got a decent sized fmic on my eclipse. a 14b turbo, about 15psi, stock injectors, 3" ls1 maf, maft, all hard pipes dejon tool. i'm tuned fine when i race. my o2's are around .94 all thru my WOT runs. my egts climb to 1550/1600 around the very end of my 1/4 mile. i run third gear ALL the way out to around 7krpm. i trap around 103-105 mph. my question is, last week i took a trip to oklahoma and back, and in fifth gear cruising around 90-100mph rpms around 3500-4000, and my egts stayed around 1550-1600. that seems really hot for such low cruising rpms. my thought was maybe my fmic is TOO effecient, and even at a 95mph cruise at 35k rpms, under no boost, the natrually aspariated air is being cooled down too much by the intercooler, with my stock 450cc injectors. any thoughts? at the same rpms, in a lower gear, at a lower speed, still not under boost, my egts are usually around 1300.

 

[CanadianTSi]

My EGT's get up to 800 celcious when i'm cruising around 90mph

 

[starr]

well thats 1472 celcius. anybody else? that cant be normal. how am i supposed to go faster if it gets that hot, or how do i cool myself down?

 

[yo2001]

not enough timing will incease your EGT. You really can't do much unless you get a 1G CAS and add timing.

 

[Bastard1g]

are you logging your runs? are you using narrowband 02's for tuning? Ok, there are many ways to cool down cylinders. You can richen the a/f ratio but that will cause a decrease in performance and increased emmisions, lower the static compression ratio which will lead to reduced performance and fuel efficiency or you can recycle your exhaust gasses
(egr valve) Egr valves work great for closed loop cruising. I dont have time to get into it now but it is alot more efficient than the first 2 options. Of course there can be other ways to solve this problem but I am talking about closed loop crusing. Also there is vct but not for our cars. Anyway, check your egr valve and log your runs and last but not least, check a wideband for accurate 02's. Also, list your mod list so we could see what you are working with.

 

[Bastard1g]

not enough timing will incease your EGT. You really can't do much unless you get a 1G CAS and add timing.

Im sorry but I dont see how retarded timing will increase cylinder temps? are you sure you dont have it the other way around? Modern automotive engines use ignition timing advance to suite the design of the motor and to help reduce combustion lag. I dont see how combustion lag would increase cylinder temps. If you know what you are talking about, I would love to hear how.

 

[yo2001]

Why? I think it's bacause the fuel doesn't have time to combust fully when it's go close to TCD or ATDC. SAme reason anti lag causes high EGT. I didn't same cylinder temp. Try put the timing after TDC and see what happends to EGT.

I'm logging WBO2, EGT, Knock, timing, Injector D/C and RPM. Thanks to Zeitronix and Datalogger.

 

[Bastard1g]

Why? I think it's bacause the fuel doesn't have time to combust fully when it's go close to TCD or ATDC. SAme reason anti lag causes high EGT. I didn't same cylinder temp. Try put the timing after TDC and see what happends to EGT.

I'm logging WBO2, EGT, Knock, timing, Injector D/C and RPM. Thanks to Zeitronix and Datalogger.

Rule number 3. No Guesses - if you don't know, don't reply - don't spread misinformation (no "I think" or "I guess" or "I've heard").


I am not even going to dignify that statement with a response. Please do not spread misinformation over the net.

 

[coltboostin]

yo2001 is correct in his theory. What do you think happens durring an anti-lag launch?.....

 

[yo2001]

I was being nice.

 

[Bastard1g]

yo2001 is correct in his theory. What do you think happens durring an anti-lag launch?.....

I dont know, you tell me. I am not trying to be mean about it but I would really like to know your theory.

 

[pneumo]

Retarded timing won't increase cylinder temps, but it will increase temps in the exhaust manifold where EGT's are read. That's because if timing is retarded far enough the fuel will still be burning when the exhaust valve opens, shooting flames onto the EGT probe. Since knock retards timing, high EGT's are a sign of excessive knock, which could be happening to Starrs car during cruising. I recomend adding a few percent more fuel at low throtte, 3500-4000 rpm range.

Your EGT's are just about perfect for a 1/4 mile run.

Your EGT's while cruising have nothing to do with the FMIC.

 

[Bastard1g]

Yes, Thank you. Really good explanation. Running rich can cause knock. My point is that if he is running such low timing that he is not burning fuel, then there is something wrong anyway. These are not the good ole days with vaccum advanced timing. His timing isnt the issue here. His a/f ratio needs to be corrected since cruising at 90 mph puts him in open loop mode. this is why if people say things, they need to explain why they said what they said. Like I said, no offense, I just can not understand slang terms and vague theory's. I try to avoid it cause it leads to confusion. With that said, personal experience leads me to believe that his a/f ratio is lean and he needs to richen things up a lil. Allthough in theory , denser air could be leaning him out slightly enough but I doubt it. I have a full 6 bolt swap in my 98 gst with a 1g cas and I wouldn't add timing if I am getting high egt's. Thats why you cant really trust egt's.