extremely high egt's

[ktmryan53]

ok i did search but didnt find anyone with actual temps for the term "extremely hot". my egt gauge is going to 1400+ degrees when traveling one city block, 3-4 /10th of a mile. i did get it to max out the autometer gauge at 1600 just to see it. im idleing 1k-1100 degrees. this condition occured after my 6 bolt swap.i have a tubular manifold so yes it gets hot but should dissapate quicker. the coolant temp is staying completely normal and there is the proper amount of fluid. i understand its running rich so i did a boost leak test with only one small leak that i fixed. the car was nowhere near these temps before the swap and i know they should glow after a long amount of hard driving.
relevant mods
50trim 22psi,680cc, walbro,safc2, fmic,typical stuff.

 

[eclipsegsx1736]

wow, that IS hot. Can you post a log or something? Unless your sensor is hosed, your timing could be way off or could be very low, from a horrible case of phantom knock or something. Still, I don't see how it can be that high at idle, unless this is after a very hard run.

 

[PSI NRG]

Where do you have the probe tapped? IF you have it tapped in the manifold it could very well reach those temps. I would be more conered if it was in o2 housing or down pipe. Think about it when you run a turbo car hard you can easily get it to glow and thats pretty freakin hot. My manifold glows but my a/f ratio sits right at 11.3 and does not move. I would be more worried about what the a/f gauge is reading then the egt.

 

[Echo5Zulu]

Where do you have the probe tapped? IF you have it tapped in the manifold it could very well reach those temps. I would be more conered if it was in o2 housing or down pipe. Think about it when you run a turbo car hard you can easily get it to glow and thats pretty freakin hot. My manifold glows but my a/f ratio sits right at 11.3 and does not move. I would be more worried about what the a/f gauge is reading then the egt.

Correct, those arent too far off of mine and Im mounted like 2 inches off in the manifold. Make sure your a/f ratios are correct. Keep in mind lean=hot, and adding fuel will cool things down but too much fuel will also kill power. Its all about balance and getting the correct a/f ratios. 1900f would be bad.

 

[andymoraitis]

Too rich can also create high EGT's. I've seen instances where the excess fuel was combusting inside the exhaust manifold and causing EGT numbers to rise dramatically. The fact of the matter is that high EGT doesn't always clue you in exactly to what's wrong, only that something is. A wideband would be perfect in determining which way you need to go.

 

[wishihadatalon]

Correct, those arent too far off of mine and Im mounted like 2 inches off in the manifold. Make sure your a/f ratios are correct. Keep in mind lean=hot, and adding fuel will cool things down but too much fuel will also kill power. Its all about balance and getting the correct a/f ratios. 1900f would be bad.

Correct afrs and correct timing. Thankfully the stock ecu has a really good timing map that allows you to just use afrs. As Andy stated you can run to rich and have high egts. I would be concerened with anything over 1600f as being to hot but I guess that is just me.

 

[Kevin Jewer]

I'm guessing the knock sensor was installed too loose, too tight, or just plain shit the bed at the time it was moved to the 6 bolt block. AFR being off isn't going to cause temps that high on these motors, but low timing will.

 

[SleeperG]

Even your idle egt is way off.

i idle between 750 and 900 on average. depending on what i was doing prior to the idle.
I have a sbr manifold tapped in the #1


something is definatly a miss

 

[siceclipse]

andy is correct with the too much fuel causeing high EGT's

In another thread of mine i talked about comming home (Connecticut) from Vermont and noticing my EGT's were 14-1450 on cruise and climbing steadily with light acceleration.

After calling a couple places, Aaron, at Victor Research told me to lean it out a little and see what happens.

I took 5-7% more fuel out and now i cruise at 1300 and idle at 900-950.

 

[andymoraitis]

Kevin's point about timing is more accurate though. I think most of the problems people have are related to both, but low timing will have a much larger effect on high EGT than running rich will. It's not a bad idea to look at both areas though.

 

[PSI NRG]

Kevin's point about timing is more accurate though. I think most of the problems people have are related to both, but low timing will have a much larger effect on high EGT than running rich will. It's not a bad idea to look at both areas though.

How much could timing be off if hes not running cam gears or something for it to reach those temps? Couldnt he also have a bad cam angle sensor? If timing is way off?

 

[andymoraitis]

I'm talking about ignition timing not valve timing. I suppose the CAS could be a problem, but I can't be sure without him testing it. Knock that pulls timing will also cause high EGT's (among other things). I'd be more suspicious of that since he's tuning 680's on an AFC. Of course an idea of the correction factors used and a log would be the most helpful.

 

[ktmryan53]

the probe is on the #1 cylinder halfway between the head and turbo. i already tried switching the cas. i previously had the 800-900 idle temp numbers and never higher then 1400 even if i was really putting alot of load on it. my correction factor on the safc 2 is-4.0%. from idle to about 3800rpm(i believe) it stays at 0.0% and then above it in the 4k range it increases to positive numbers. i also think that a good possiblity is the timing being off. so you guys are saying the knock sensor could be bad? i know the knock count on the safc says at 0% no matter how i drive it and im sure that is INcorrect.

 

[silvah_gsx]

Your correction factor is -4% with 680cc injectors? WTF -4 is where you'd be on the stock 450cc injectors. You're running WAY too rich. You want to be down below -30% as a baseline with 680 injectors.

Also 2g ECUs don't show knock for some reason, so your AFC will read 0 on knock. That's something for later though, once you get that correction factor sorted out

 

[Rice Over Wheat]

Yeah on my 450s tune and stock smic, I was -5%. I'm about to toss in 650s using that -30% baseline. If you are going positive for correction at 4k+ rpm, that seems just wrong. You should be starting from your baseline and increasingly negative from there. I'm surprised your car even runs.

As for your temps, my egt is tapped #1 runner. I idle at 900F, cruise at 1100, and only hit 1300 ~ 1400 on the highway at 85+ mph or WOT.

 

[4g63swap]

bet he has a gm mas and a maf-t.

 

[ktmryan53]

well i didnt tune or really add any parts to the car. it does run undoubtly rich but did pass emissions. dsmlink will be in shortly. im not sure but it does have a chip for the injector size, ect. i have a gm mas and maft but not on this car. in fact on my other car i just went aem ems.

 

[awddsm95]

I think that it is important to mention this. The highest EGT's will be had at a 14.7:1 AFR for a given amount of Ignition timing. Leaner or richer will actually result in a decrease of exhaust gas temperature at that given ignition timing. If you thinking about it, with stoichometric being what it is, (idealy all the fuel and all the air will be used) would yeild the highest EGT's. Richer puts more fuel to absorb heat, and leaner is like lighting a fire in a desert. Either way there is either an extremely dense mixture such as a dense forest or not enough to burn such as a desert. Think about it.

Everything else mentioned about too much fuel (igniting in the manifold) is correct.

Kyle Deiwert
Mechanical Engineer

 

[Kevin Jewer]

That's an interesting theory about AFR on either side of stoich resulting in a lower EGT. In fact I might agree with it after I think about it some more, despite a very strange analogy. But the fact remains that being too rich (not sure what the definition of "too rich" is in this context, perhaps 9:1 and down? I didn't have a WB when doing these tests with the EGT) causes higher EGTs due to some fuel still burning as it passes the probe. I have seen being too lean cause low EGTs as well. Once by accident I ended up about 30% leaner than I should have been. EGTs were very low, and there wasn't enough combustion energy to support acceleration.

 

[awddsm95]

Like I mentioned before, I agree that it is possible to be so rich (a mixture that after combustion still has such a high content of fuel and enough air to ignite) that combustion is talking place in the exhaust manifold, after the actual combustion event in the cylinder has finished.

If this is the case though, the high EGT's are not being caused by high cylinder temperatures (the reason we look at EGT's!!) but combustion in the manifold itself.

So the question remains (mind you I may not agree with this based on the purpose of this discussion), is this entirely bad on a turbo car, where heat induces flow through the turbo, which can lead to better spool up characteristics (as long as we are not melting components)?

Some rally cars not only retard their timing for anti lag, but also induce a state of rich mixture to the manifold via intake injectors or an entirly seperate injector in the exhaust manifold.

Think about it.

 

[delta448]

I'm talking about ignition timing not valve timing. I suppose the CAS could be a problem, but I can't be sure without him testing it. Knock that pulls timing will also cause high EGT's (among other things). I'd be more suspicious of that since he's tuning 680's on an AFC. Of course an idea of the correction factors used and a log would be the most helpful.

+1

My first thought was: 680's and SAFC!!? So, my question is, would the AFC affect timing enough to cause knock the ecu can't deal with because of the injector size? Or, would the injectors be enough that the low correction factor causes fuel to be burned in the mani? If so for either of these, wouldn't that be your answer?

 

[Kevin Jewer]

Please stop saying "think about it," it's beginning to bother me. I think about many things, whether with your permission, or without.

If this is the case though, the high EGT's are not being caused by high cylinder temperatures (the reason we look at EGT's!!) but combustion in the manifold itself.

This statement loses me. EGTs are hardly related at all to cylinder temperatures on our cars, because of ignition retard, as discussed above. Your previous post makes the disclaimer "for a given amount of Ignition timing," but I think we just went back 10 steps.

 

[awddsm95]

Sorry about the "think about it", it really was not directed towards anyone in particular, I just think that it is important for people in general to come to their own conclusions and not just accept words from another, and for anyone reading this, I dont want them to just take my word for it, I want them to use their mind and decide for themselves.

If you look at the 4 stroke combution cycle, ignition firing occurs on the compression stroke before the pistions reaches TDC. The number of degrees your spark plug fires before it reaches TDC is known as ignition advance. If you look at the trends of ignition advance, as load goes up [boost or manifold pressure (although our cars load is not calculated based on speed density)] advance goes down due closer proximety of the molecules in the combution chamber. It takes the flame less time to propogate across the cylinder with a more dense mixture. So if a cylinder is running rich enough to not detonate (although fuel quantity is only one factor that can lead to detonation) it will always have ignition advance (spark BTDC). Retard can mean two things. Either pulling timing (less advance than before) or spark after TDC. Spark ATDC produces hardly any torque, but is what people do for "antilag" when shifting/launching. A spark enough after TDC would cause the mixture to be burning even when the exhaust valve opens and would dramaticly increase EGT's. But like I said, you will, for the purposes of this conversation, never have a spark ATDC in your car.

I guess i dont know what loses you about the statement I made. EGT's are completly related to cylinder temperatures in all cars. Ignition advance can cause dramatic changes in EGT. For the situation being discussed above, we are assuming enough advance, (lets say a conservative 15degrees) to produce good torque, and a extremely rich AFR. The High EGT's could be caused by the extremely rich mixture igniting in the manifold.

 

[Kevin Jewer]

I get a little cranky after my 14 hour night shifts, it's likely that I should be the one apologizing. I certainly appreciate the discussion. That being said...

Ignition advance in our cars is never set to the ideal value (max torque at that particular load/rpm) due the the need to suppress detonation due to higher cylinder pressure/heat. The amount of timing everyone runs is different (people are constantly sending me logs or having me tune thier cars, so I have a pretty good idea of the range of timing alues people have to run on various setups, fuels, locations, etc). This has a huge affect on EGT.

In a non-turbo car ignition timing is much more standard, there isn't a ton of tuning that goes on there. It also does not change, since knock retard is generally not used (it s on some modern high compression motors, but shouldn't kick in oten at all). NT tuners can actually advance timing far enough to reduce torque at the current load/rpm cell before knocking. This makes EGT a MUCH better indicator of AFR.

In our case the ECU is always assing around with timing. Even just normal knock "noise" causes up to 1-2 degrees of knock retard, which in my experience has a significant effect on EGT, and renders EGT as a measure of AFR completely useless.

This is based on my experience running an EGT guage on a turbo DSM, YMMV, and if we have to agree to disagree I'm ok with that. It's a good discussion either way.