EGT Temps

[chevota]

I'm curious what the max safe EGT is on an M278, reading from the oem PID.
In my tinkering my EGT at full load is usually ~1050-1250F, mostly because I can't lean on it for very long. There was a couple times it exceeded 1300 while floored for >5 seconds. It makes me worry that if it had been a 1/4 mile run or worse, if it would continue to climb. So what temp is too much?

I looked at some runs that others posted, which is slim pickins, plus most people don't add EGT, but an M156 hit 1660 stock, then 1780 tuned, but all the M278 engines were ~1250-1320.
Is the EGT sensor before the turbo? Seems like it must be, but I have no clue where it is.

[Schnell]

EGT is read from the wideband sensors.

[chevota]

Thanks. I wondered if that was the case since I can't see a TC anywhere. Seems odd considering how far away it is from where it needs to be, but I guess that was the economical factory decision.
I managed to do my first ever 0-100 run yesterday and it hit a max of 1182F. Possibly because it wasn't so frikkin hot out, with ambient of 73F.

Not sure why it broke 1300 before, but maybe because ambient temps were >100? So I feel pretty good about that temp, compared to other peoples runs.

[Schnell]

I've seen 1400+. If your lambda looks good and there's no KR, probably the only concern would be the catalyst material.

[chevota]

My Lambda is often all over the place because it switches fuel maps back n forth. Even when it stays on one map the Lambda doesn't exactly follow that map. Like Spark, where I ask for xx spark but it probably won't do it. So generally I'm just pushing spark and fuel in the direction I want, then see what happens.
In the 0-100 run I posted, the fuel Command spent almost all the time ~.890 or leaner. The O2's were reading all over the place but avg ~.870? I'm running 50% Ethanol so it's not really too lean (in my mind).
Since it takes a looong time for the temp to climb, it's basically impossible for me to really check it. So maybe when it says 1200 it's really 1600, but takes soooo long to read I'll never know? Unsure if that time delay is because of the distance between the cyl and sensor, or the sensor is slow, or both.

In the end, considering the other M278 runs I saw, I feel like I'm ok, but then there's the whole thing about M278 cooking Ex valve guides... So then I'm back to nervous, but also wonder about VVT. The Ex valve timing on the M278 is very advanced under load and it makes no sense to me. Does MB feel like it needs to be like that for power, or is it emissions? Maybe it's the cause of the valve issue, or maybe an attempt to fix the issue? I retarded the timing 10deg to see what would happen, but all it did was sound different, so my guess is emissions.

If there's any KR it's just one random cyl, for a moment, in the whole run, and not repeatable run to run.

While on the topic of Lambda, here's a question (for anyone) that has been buggin me forever: How does a wideband read richer than Lambda? Lambda means the use of all O2, so no O2 left to read. A Lambda of .9, .8, .7 would also be zero O2.... I'm sure there's some trace O2 left over but I'm sure that amount would be random.