Tuning with EGT

[adam g]

Does knowing the exhaust gas temp really help with engine mapping or give any warning signs of something wrong. There seem to be so many factors that can alter it that i dont see how i could use it effectively. Also there isnt really a target to aim for from what i have read. Would be interested in the experiences from this forum.

[AndyP]

Depends where your sensor is mounted, I've been told that 900°C pre turbo or 800°C post turbo is safe. Mine goes to about 765°C in 6th, uphill, that's with the sensor mounted in the very top of the downpipe.

[quattro-nick]

if your AFR or ignition is not properly adjusted than you get high egt values

[GazzaG60]

Egt I feel helps. I remember a Subaru being saved due to us noticing high egt, it burned through the ported header luckily and didn't melt

[adam g]

So basically, it should be used to ensure you dont go over a certain threshold that is typical for your engine (800 post turbo in my case) to prevent melting something.

What can cause EGT to increase? From what I've read too much timing advance or too much timing retard (so doesn't help to tune timing much). I imagine increasing boost pressure sends it up too? Does ambient temp have a significant effect or is this negligible against the temp created by the burn.

[GazzaG60]

Low timing is a key to high egt as is lean run
Tune for af for stoich. Timng also adds in my experience more hp than boost ie 1deg v 1psi

[quattro84]

Tuning 101 guys, don't mean to be rude but read a book.
In short: Increase timing ->MFB moves to TDC, PFP rises, so does chance of uncontrolled ignition. More timing does not always equal more power. That's where reading the book comes in.
Reducing timing -> MFB moves from TDC and with other factors that dictate engine flow (valve timing/overlap/vol eff./backpressure) and enthalpy (fueling) gives higher EGT readings.

Key is to find MFB for your/our setup and tune it to run it there for best efficiency in power delivery, and compensate to marginate against limitations.
I don't understand why one would like to run with permanent displayment of EGT temps when your ECU is not capable of compensating, once mapping is done and you'd notice it most likely it's too late to respond anyway.

[AndyP]

And for those who don't know what MFB is ( I had to look it up ) here's a little light reading for you

http://ilot.edu.pl/KONES/2002/02/str193.pdf

[Tonybolony]

And for those who don't know what MFB is ( I had to look it up ) here's a little light reading for you

http://ilot.edu.pl/KONES/2002/02/str193.pdf

Light reading??

Might be an idea to forward that to the Fast Ford forum- I'm sure there are plenty of 17 year old ST drivers that understand it all, as well as I did

[quattro84]

MFB is the parameter to watch while calibrating an engine. Since you (neither do i, but i do work with it) don't run with indicating systems nor in cylinder pressure sensors this is hard to achieve.
PFP is your in cylinder peak pressure which will limit your hardware. Piston & pin will budge, conrods buckle and finally the head gasket blows.

What i am trying to say is that there is no general number to tune for when using EGT. You need to add robustness to compensate for inlet air temp (IC efficiency) altitude (oxygen starvation) and finally hardware deterioration so when your tunable ECU is setup at sea level at 15 deg ambient temp and you tune for max 900deg at the turbine inlet this can read 200deg higher with same ECU calibration in a hot summer climbing on altitude few years after mapping. (if your ECU has no form of compensation, that is)

I cannot give a clear answer what your max temp should be for your setup. Since you aren't running lean burn you will most likely be safe with current hardware to run 950 deg in, i'd say aim lower and if you have a chance on a dyno see what you gain in performance if you would try to maximize it temperature-wise.

Perhaps PRJ (Dimitri) wants to share what he reckons to be a safe operating temperature for the S2 head/valve/mani/turbi. AFAIK later RS models run lean burn upto 975deg from where enrichment starts to control turbine in temperature.

[JariP]

What do you mean by lean burn? What kind of AFR's?

[prj]

What do you mean by lean burn? What kind of AFR's?

Lambda 1 until **** hits the fan and fuel is emergency dumped. 750c pre-control and 975c hard limit.
That's why all the RS4 heads are cracked.

RS6 runs lambda 0.95 and has no pre-control, only the hard shutdown. That's why manifolds crack.

Everything for fuel efficiency… Anyway 850C post-turbo and 1000c pre-turbo are the limits to watch for in I5. As for how EGT is affected, it's already been said - read a book, the forum is not the correct place to learn about such things.

[quattro84]

Thanks for your post Dimitri, much appreciated.
Do have a question perhaps you know the answer. I've read that the RS4 EGT modules can only monitor a small operating window from 800ish -1000ish degrees since that's the area for the controller to react, while the RS6 modules read full range from -40 to 1100 degrees. Can you confirm? Do you know why they coded it this way?

For the later RS models the need to run lean is mostly due to emissions, VW FSI on Euro4 spec run up to 4 different operating modes in order to reach the desired NOx level set by legislation. Page 13: http://www.volkspage.net/technik/ssp/ssp/SSP_322.pdf

Stuff is only getting worse with EGAS. Your feedback will be translated and dictated by ECU, so abrupt throttling will be filtered to give a smoother fueling to keep emissions and temperature deviations low. Engine response is no longer mechanically limited but mapped by the ECU.
Pro: One can calibrate the EGAS pos in idle to make antilag https://www.youtube.com/watch?v=u3sxtQwUMkE

[quattro84]

What do you mean by lean burn? What kind of AFR's?

Lambda =1 / AFR 14.7 (non alcohol blends) or more if the engine can manage. For DI engines like Toyota with stratisfied injection combined with port injection they manage Lambda 1.4 (AFR=20) on part loads...

[prj]

Thanks for your post Dimitri, much appreciated.
Do have a question perhaps you know the answer. I've read that the RS4 EGT modules can only monitor a small operating window from 800ish -1000ish degrees since that's the area for the controller to react

950C+

while the RS6 modules read full range from -40 to 1100 degrees. Can you confirm? Do you know why they coded it this way?

Because RS6 is newer.