can running too rich cause high egt's?

[terminaltsi]

ok, i'm using 625 cc in jectors, 50 trim, all supporting mods. my safc right now on high is set at -7% at all rpms over 5000 and my egt is still getting close to 900 degrees C by 6500 rpm. boost is only at 16 psi. how is that possible? isn't a typical setting closer to -15-20% at the same settings? how can i still be lean?
i've logged the car and have no knock and full timing, but egt's get way too high over 6k.

any ideas?

 

[1LE]

Sounds like it's too rich.

 

[terminaltsi]

Sounds like it's too rich.

it seems that way, because there's no reason i should be where i am on the safc settings...but when i see those egt's skyrocket towards 900C i can only think lean....unless someone can actually tell me that really rich will also cause high egts.....

 

[OB1]

it seems that way, because there's no reason i should be where i am on the safc settings...but when i see those egt's skyrocket towards 900C i can only think lean....unless someone can actually tell me that really rich will also cause high egts.....

Yes really rich will cause high EGT's because the air/fuel mixture is still burning as the exhaust valave opens thereby sending fire through your manifold and superheating your EGT probe. Then the extra hot manifold send the heat back into the head which increases the chance of pre-ignition and/or detonation which will further increase EGT's.

 

[terminaltsi]

Yes really rich will cause high EGT's because the air/fuel mixture is still burning as the exhaust valave opens thereby sending fire through your manifold and superheating your EGT probe. Then the extra hot manifold send the heat back into the head which increases the chance of pre-ignition and/or detonation which will further increase EGT's.

ok, good info. however my logs show no knock. maybe because i'm not quite rich enough to cause that yet? maybe ii'll try to lean it out. i just got nervous when i saw the egt's climbing, so i added fuel.

 

[gixrman]

Running lean and high timming can also cause high EGT's.

 

[terminaltsi]

Running lean and high timming can also cause high EGT's.

well i know i'm not lean bcause i have no knock and my timing is 19-23 degrees at wot.

 

[OB1]

ok, good info. however my logs show no knock. maybe because i'm not quite rich enough to cause that yet? maybe ii'll try to lean it out. i just got nervous when i saw the egt's climbing, so i added fuel.

Pull your plugs to see if you really are running rich. If they come out drenched in fuel then I would start to lean your setting out.

Theoretically you should be at (450/625 - 1) or -28% or thereabouts. Unless you are running HRC 625 which I believe flow more like 580 so -22% or so.

BTW, EGT's up to 900 are not necessarily going to blow your motor. I would try to stay under 850 myslef.

Keep in mind, when you are adjust airflow reading for large injectors, your telling the ECU that there is less and less airflowing, so the ECU in turn advances timing. On a 50 trim, at 20psi or so, I like to keep my timing total advance around 16-17 degrees.

Don't be afraid to lean things out but do keep a close eye on your timing curve. ANy flat spots and more importantly any dips are definitley a red flag.

G/L!

 

[terminaltsi]

Pull your plugs to see if you really are running rich. If they come out drenched in fuel then I would start to lean your setting out.

Theoretically you should be at (450/625 - 1) or -28% or thereabouts. Unless you are running HRC 625 which I believe flow more like 580 so -22% or so.

BTW, EGT's up to 900 are not necessarily going to blow your motor. I would try to stay under 850 myslef.

Keep in mind, when you are adjust airflow reading for large injectors, your telling the ECU that there is less and less airflowing, so the ECU in turn advances timing. On a 50 trim, at 20psi or so, I like to keep my timing total advance around 16-17 degrees.

Don't be afraid to lean things out but do keep a close eye on your timing curve. ANy flat spots and more importantly any dips are definitley a red flag.

G/L!

i guesss i'll start leaning it out and logging and see what happens. i'll post with results.
thanks.

 

[terminaltsi]

ok, thisis really weird. i slowly took out fuel a couple % at a time while making runs and logging until i arrived at -38% on high and STILL no knock. EGT's still hitting 900C by 6300 rpm. wtf?

 

[gixrman]

Did you reset your ECU? What was your timming curve like?

 

[OB1]

You went from -7% to -38% and still no pulled timing???


You are going to have to give us more information:

What injectors and fuel pump are you running?

What are your low AFC settings because they do impact your WOT tune. I am assuming you set your low settings accurately first then proceeded to do the high settings.

Also list your high settings.

 

[terminaltsi]

ok... walbro 255 hp, rewired, 625 cc injectors, unknown brand (they came from another car that my girl just bought and she doesn't need them yet)

lo settings are equivalent to the highs averageing -35%. yes the lo settings were set first and car ran well.....fuel trims around 110%. part throttle the car runs much better, egt's stay around 820c.

high settings -25 at everything below 4k, 5k goes to -30 and over 5k is -38%. sounds weird but it's the only way the car even begins to perform well.

 

[guitarXgeek]

Running lean and high timming can also cause high EGT's.

Just to clarify, too low timing will also increase EGTs. Therefore, retarding timing isn't always a good solution to control knock because you may end up melting your pistons if you retard timing too much Just thought I'd throw that in, even though it doesn't necessarily help your case right now it may help later on down the road

 

[OB1]

ok... walbro 255 hp, rewired, 625 cc injectors, unknown brand (they came from another car that my girl just bought and she doesn't need them yet)

lo settings are equivalent to the highs averageing -35%. yes the lo settings were set first and car ran well.....fuel trims around 110%. part throttle the car runs much better, egt's stay around 820c.

high settings -25 at everything below 4k, 5k goes to -30 and over 5k is -38%. sounds weird but it's the only way the car even begins to perform well.

-38% is way off the theoretically correct setting of -28%.

I would start by redoing your low and mid fuel trims to get them close to 100%. In your case it probably involves going 3-4% richer.

The fact that you are still not seeing knock, yet your EGT's are climing to 900 suggests you may infact be detonating but your knock sensor is not picking it up.

How old is the knock sensor? Have a quick look at to make sure the black tar like stuff hasn't melted off the back of it. If it is the original I would replace it.

 

[terminaltsi]

-38% is way off the theoretically correct setting of -28%.

I would start by redoing your low and mid fuel trims to get them close to 100%. In your case it probably involves going 3-4% richer.

The fact that you are still not seeing knock, yet your EGT's are climing to 900 suggests you may infact be detonating but your knock sensor is not picking it up.

How old is the knock sensor? Have a quick look at to make sure the black tar like stuff hasn't melted off the back of it. If it is the original I would replace it.

well, last night i reset the ecu, then reset my lo settings to get fuel trims at 100%. stft and ltft are now at 100% but mid is around 119%, still trying to get that right. moved my highs around in all directions, found that -38% is indeed too lean....car almost dies when i floor it. moved highs to around -20% but egts still skyrocketing.

note: knock is still nonexistent. found maybe 2 or 3 counts every now and then but nothing consistent. btw, the knock sensor is new, put that on last year when i put the head on. i did think of that though but remembered that it's new.

going to check my timing today and make sure it's correct.

 

[guitarXgeek]

yet your EGT's are climing to 900 suggests you may infact be detonating but your knock sensor is not picking it up.

I'm pretty sure that if this were the case, he would have major engine damage because of all the detonation before he saw a significant raise in EGT like this I highly doubt this is what's happening. The MAIN reason that detonation raises EGT is because of the knock sensor telling the ecu to retard ignition timing. The actual detonation event doesn't do all that much in regards to EGT. That's why I think he'd start blowing out seals and gaskets before he saw much of an increase in EGT if the knock sensor was dead.

 

[terminaltsi]

well i dont know why the knock sensor wasn't picking up knock at -38% and so on, but i do know that now i have the safc set at -2% on high and it runs like a champ. pulls hard, egts slightly above 800C.
obviously whatever injectors these are, they aren't 625's.... but at 1.2 bar boost it's running great. for more boost however, i am going to have to get some larger injectors!
thanks for everyone's help and input.