Author Topic: aan High Egt Problem  (Read 14314 times)

Offline kriskis

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aan High Egt Problem
« on: October 18, 2010, 09:56:40 pm »
I have a problem with the egt is too high at speeds above 6400 rpm until the end of 7200 rpm or below 6400rpm is normal, I will link to the logs from vems maybe someone could help me
my logs
http://wrzucacz.pl/file/3371287155269/1287434651/96c26901b3bcd2a03b08248943a6f169?download

my tables
http://wgrajzdjecie.pl/zdjecia/778a07905f1939ec150c669d8a67edf7.jpg
http://wgrajzdjecie.pl/zdjecia/66ad72242c2091b6c6fe29d881cd73ae.jpg
(my car audi s4 c4 20v turbo 82.5 bore comp ratio 8:1, garrett t67 boost 2,3 bar injectors 1000cc at 4 bar )
« Last Edit: October 18, 2010, 09:59:56 pm by kriskis »

Offline mattias

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Re: aan High Egt Problem
« Reply #1 on: October 18, 2010, 10:48:16 pm »
You are running insanely rich at many load sites, and I think perhaps too much ignition advance even with your lowered c/r of 8:1.
On the other hand, running that rich is what saves the engine from the high ignition advance since it will not build much cylinder pressure with such a rich/slow burn.
Anything richer than lambda 0.80 on regular gasoline will loose a lot of torque/power and cause potential mis-fires, there are some spots in the log where the TPS signal is severly distorted because of radio-interference from mis-fires. This can cause trigger errors and  havoc with TPS-based acceleration enrichment.

I don't see a real problem with your exhaust temperature, there are too many errors in the tune to really see what's going on. The turbo seems to be way too large and slow (Garret T67 is a dinosaur, old tech) which means it really is only at full boost above 6000 rpm anyway, which will make the temperature increase there.   You could also have a problem with the wastegate, too little flow at low lifts will cause the spring to be badly matched to the boost level and the valve will leak exhaust pulses before it reaches full boost.  Ever done an intake pressure test?
« Last Edit: October 18, 2010, 10:49:57 pm by mattias »

Offline kriskis

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Re: aan High Egt Problem
« Reply #2 on: October 19, 2010, 07:20:15 am »


"Ever done an intake pressure test?"


 you're probably thinking of measuring the pressure at the exhaust? if so, I did not do such a test has turbo .63 ar hot side this may be the cause of high egt, what should be the maximum pressure in the exhaust manifold.
I have such a rich-fuel ratio so that the lower the temperature because it goes beyond 900 degrees at full speed third gear. I can send you the entire map and you look threw what could be wrong

Offline Erikk

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Re: aan High Egt Problem
« Reply #3 on: October 19, 2010, 11:26:12 am »


"Ever done an intake pressure test?"


 you're probably thinking of measuring the pressure at the exhaust? if so, I did not do such a test has turbo .63 ar hot side this may be the cause of high egt, what should be the maximum pressure in the exhaust manifold.
I have such a rich-fuel ratio so that the lower the temperature because it goes beyond 900 degrees at full speed third gear. I can send you the entire map and you look threw what could be wrong

No. He means putting pressure on the whole intake system, from turbo inlet to the intake valves.

Sweden - erik.englund@gmail.com

Offline mattias

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Re: aan High Egt Problem
« Reply #4 on: October 19, 2010, 01:59:41 pm »


"Ever done an intake pressure test?"


 you're probably thinking of measuring the pressure at the exhaust? if so, I did not do such a test has turbo .63 ar hot side this may be the cause of high egt, what should be the maximum pressure in the exhaust manifold.
I have such a rich-fuel ratio so that the lower the temperature because it goes beyond 900 degrees at full speed third gear. I can send you the entire map and you look threw what could be wrong

Like Erik said I meant an intake leak test, I made another post here about how to do that :
http://195.159.109.134/vemsuk/forum/index.php/topic,1451.msg15111.html#msg15111


While tuning you can monitor the exhaust manifold pressure right before the turbo to get an idea of how much load you are putting into the turbo. You must use some kind of mechanical filter to dampen the pulses. You only need to drill maybe 1.5 mm hole and use a brake line nipple to connect a pipe for the first part away from the hot exhaust, then use rubber line up to a mechanical gauge or appropriate MAP sensor (7 bar capable).
Once you start to have more exhaust back pressure than intake boost pressure you must be careful. Any intake leaks will stress the turbo a lot more and create higher exhaust back pressure.


The A/R of the hot side of the turbo is not important, 0.63 tells me absolutely nothing - the wheel is the real obstruction and you generally need to know the turbine wheel inducer/exducer measurement. Most likely this turbo is using old technology, sure it could be brand new - but still use old tech.  I have seen modern diesel turbo chargers that are larger than what you have spool a lot earlier, these are new/high tech with low pressure efficient turbines.


You are wrong to run super rich, you kill the efficiency of the combustion. The most effective way to lower the exhaust gas temperature is to use more ignition advance, up to the point where you become knock limited. If you get to that point you need to make mechanical changes to the engine to use that kind of boost pressure. I would sort out the engine and tune at a lower boost to begin with, so that you don't grenade the engine while testing these changes. It's a progressive process and takes time, but not so slow if you use good methods. Make sure the basics work first. KISS = Keep it simple stupid. :)

You should upgrade to 1.1.81 firmware and VemsTune, then go from there, it is much more capable.

Offline kriskis

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Re: aan High Egt Problem
« Reply #5 on: October 19, 2010, 09:30:53 pm »
My back pressure in the exhaust manifold at 2.3 bar boost is 2.8 bar when it comes to leaks in the intake manifold is completely sealed the valves are tight because they had just been made head, I have a 50 mm wastegate

Offline mattias

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Re: aan High Egt Problem
« Reply #6 on: October 19, 2010, 10:13:11 pm »
Great to see numbers on the exhaust back pressure.
Is the compressor inducer on your turbo 67 mm ?
If it is, it should be capable of flowing enough for at least 700 bhp.

If there are no leaks in the intake plumbing, and judging by your injector duty cycle (70-75%) and running super rich, the turbo could be at it's limit - question is if you have the torque to prove it.

What quality of gasoline do you run? It's quite difficult to run pump gas on an engine like this with so much boost.

About intake leak testing, I'm not talking about the intake valve seats being in good order and sealing properly. I'm talking about every part of your intake plumbing, from the compressor inlet upto the head.   Did you perform an intake leak test like the one I described? It takes very little time to do with simple equipment.

About exhaust temperature measurements, you have to realise it's very important to only compare numbers with others who use the same sensor and placement. Your sensor seems quite fast, and if measured in the exhaust port of a cylinder then 850C is expected at this power level and probably little you can do about lowering it. Different engines have different working temperatures, and the load is high on this one. There is really not much I can say to help you there.

Offline kriskis

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Re: aan High Egt Problem
« Reply #7 on: October 19, 2010, 10:39:15 pm »
my air intake system is all good and tight I am sure very sure, my turbo has a compresion wheel 67 mm and has a handle up to 800 hp. at the moment I have about 600hp. I have 3 egt two very close to the head ( 1 and 4 cyl) and one in front of the turbo from the readings in the log are the strange thing is that those close to the maximum head temperature reaches 800 degrees Celsjus and this is connected to vems is about 100 degrees with a load more because when I go on equal speed to compensate for the temperature!

The car was tuned on 98 oct fuel and I ride every day, 101 oct
« Last Edit: October 19, 2010, 10:42:36 pm by kriskis »

Offline GintsK

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Re: aan High Egt Problem
« Reply #8 on: October 20, 2010, 07:20:16 am »
If it is Audi 20VT, I usually starts to worry about EGTs when it hits 950degC. 950 for short periods also looks non harmful.
800..870deg - it is cold for this engine  ;D

Offline GintsK

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Re: aan High Egt Problem
« Reply #9 on: October 20, 2010, 08:31:35 am »
I heard from some Motronic tuner Audi RS4 EGT safety margin is even 980degC. Only above that ECU do something to protect engine.

Offline GintsK

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Re: aan High Egt Problem
« Reply #10 on: October 20, 2010, 08:38:45 am »
I do not knew how to reach low EGTs when exhaust pressures is so high. At so high pressures high EGTs is simply unavoidable. On n/a engines EGTs sometimes goes above 800deg. But if compress these gases 3 times what we can expect...

Offline kriskis

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Offline GintsK

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Re: aan High Egt Problem
« Reply #12 on: October 20, 2010, 09:21:59 pm »
Peak EGT 892degC! Do you want lower?!  :o

Offline kriskis

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Re: aan High Egt Problem
« Reply #13 on: October 20, 2010, 10:16:45 pm »
yes it's true peak maximum is 893 degrees but at 6400 rpm and at 7200 rpm that went beyond 900 degrees
good egt to be at maximum 890 degrees C at the maximum engine speed

on Friday the car will be tuned to improve fuel map so that the lambda is not going down below 0.80 (11.7 AFR)
« Last Edit: October 20, 2010, 10:22:10 pm by kriskis »

Offline mattias

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Re: aan High Egt Problem
« Reply #14 on: October 20, 2010, 11:07:49 pm »
Ok, be careful and let us know how that goes.

What wastegate do you use? and do you control boost electronically?