dpcompt

We are experiencing a pretty nasty heatwave in my hometown, Lodi,CA. I know this isn't normal for most Audi owners, but I drive my car in manual all the time. Today my car wouldn't shift into 6th in town. Would the 108deg heat have an effect on the shifting on my car.

mashani9

I never experienced that, only the reluctance to use 1st gear if not in dynamic/sport or manually shifting with the paddle. Which is a TCU tune way of saving gas I assume, but it is a good bit of the "lag" in comfort mode.

The ZF8 does have a "high temperature operation mode" where it raises the shift points and fully locks as much as possible instead of allowing slip until it cools off, but that requires the trans fluid to get close to 250 degrees F (like 120C) I believe. I don't know if it enforces those higher shift points in manual mode or not. Were your shifts a bit more "jerky / firm"? That would likely be a side effect of its desire to stay fully locked as much as possible in that case.

Otherwise, I don't know why you would not be able to upshift, unless your RPMs were not high enough.

Miss my R8

Hot conditions + AC on and car will not shift up "early", holds revs to just under 2000.
To me this would tend to generate more heat but that's how they programmed it!

dpcompt

I didn't notice any jerkiness, but it wouldn't allow me to shift into sixth. This morning before it heats up I will drive the car and see what happens. Everything else is running fine and the oil temp stayed below 210 degrees. I put the transmission in auto and it did seem to upshift later than normal. Hopefully it's just normal operation for the condition yesterday..

dpcompt

I drove the car this morning and the transmission is working as normal. I guess the car's computer is programmed under certain extremely high temperatures to keep the engine above a certain rpm level higher than normal. Who knew?

m444

Well it is not good to lug the engine too much at low RPM.

mashani9

Yeah, that would be the ZF8 TCU doing the high temperature mode thing. It requires less torque to produce a given number of watts (IE horsepower) at higher rpms, so it's actually less load on the transmission when it can keep the revs up, at least not at the extremes.

TheTurbanator

I recall some drama last summer with some tuned cars (though allegedly also affecting stock vehicles) about cylinder 6 misfires causing significant engine damage or even catastrophic failure that seemed to be tied generally to very high ambient temperatures and low-RPM lugging? Perhaps Audi has caught wind of this and decided to tweak the TCU to be a bit less willing to upshift under these conditions, that or it could be a coincidence.

m444

Article....How To Prevent Serious Damage On A Direct-Injected, Turbocharged Audi Engine: https://www.audiworld.com/articles/h...d-audi-engine/

mashani9

FWIW, one of the theories of the specific tune that was blowing up the engines is that they may have been overriding the timing changes that the base map uses to help mitigate what is described in that article. At some point the tuner put up a video trying to blame the issue on the base map by showing those timing changes, but they were just ignoring that the base map was doing exactly what it should do in that scenario, by reducing timing to prevent the knock/pre-ignition.

I don't think the issue the OP ran into was related to the LSPI ECU map timing changes at all anyway, it's a ZF thing the ZF was doing to keep itself happy, and just happened to also prevent lugging due to its behavior.

In any case, another way to help mitigate LSPI would simply to drive in S or always manually downshift before trying to pull/pass on the highway. Lugging the engine is generally bad, the only thing it is "good" for is saving a little bit of gas, but why buy an S car if you goal is to save gas?