tici

iTrader: (1)

I normally disable COT, but what about PE vs temperature?
I noticed that with the normal settings it starts to dump in fues starting from 212F. During a WOT the coolant temperature can rise above that, especially now, in summer.

Ist that normal to set the PE vs temp at zero?

Thanks - Stefano

SSpdDmon

iTrader: (10)

I try to leave as much enabled as possible. That way you tune closest to the vehicle's normal operating conditions. I turn off COT, closed-loop/STFT's (since I use a wideband), LTFT's, MAF/MAF MILS (for VE tuning - otherwise leave MAF on and make changes to MAF table), copy high spark to low (again for VE tuning), set open-loop fueling to 14.63 and PE to what I want. I filter out DFCO and low throttle (<5% throttle) driving as this is the last thing I tune. As long as you have recorded Commanded AFR and Wideband AFR, you can figure out what changes need to be made to fueling.

tici

iTrader: (1)

Yep, agree.
I run stock fan settings and dependint on when I tune WOR (night or day) the PE vs temp is adding fuel or not. I prefer to disable it, set an AFR and then reactivate it.
Well, this is something I'll try today, I'll then post the result.
A couple of times I saw really strange AFR: sometimes exactly same as the commanded value, sometimes higher. Maybe it's because of the temperature modifier...

SSpdDmon

iTrader: (10)

Weather most likely is the culprit. Humidity, barometric pressure and air temps can alter WOT results from one day to the next. That's why I don't like to set a car up at 13.0:1 AFR the day I tune it. If a high pressure front moves in the next day with different temps/humidity, the car could see a leaner AFR and it wouldn't have even been 24 hours since it was tuned. My advice is to tune the car with a good number in the leaner of the two banks (driver's side on most cars). That way, day to day variations won't put you someplace you don't want to be. That's my $0.02 at least...

tici

iTrader: (1)

When the SC is disabled I set it at 12.5 (safety first).
I try to have LTFT's around zero: in this way if it becames leaner and LTFT get positive that will adjust WOT too.
I don't like the common idea to be always negative to get cell #22 = 0 at WOT. I don't bother if it goes positive: that means it need it!

With the supercharger I also stay around 12.5, but I also inject alcohol on top of that, what brings the AFR to 11.8 - 12.0

I did my WOT tune: disabling PE vs temp really helped! Usually the AFR became higher at high RPM and I guess it was because the temp enrichment

SSpdDmon

iTrader: (10)

The thing is, when the computer adds fuel to WOT through LTFT's....it's guessing. It doesn't know it needs it. It could need it and LTFT's could still be 0. That's why it's called open loop - because it's a linear process. Here's the fuel you need....run it. There's no feedback from the exhaust to the PCM for it to make corrections, which is what effectively "closes the loop" before the whole process starts over. Here's the fuel you need....run it....make corrections....here's the fuel you need +/- corrections...run it....etc.

Mat

If I shut off my LTFT's will that effectively zero them @ WOT for a few dyno passes? I've got a wideband and my car is being stupid with + trims at WOT once in while depending on weather. I'll get the tune closer later, but I've got a dyno booked tonight.

Sorry for the mild hijack here, this is just close in relation to what is being talked about!

SSpdDmon

iTrader: (10)

Yes, turning off LTFT's will mean they're off all the time. The STFT's will still try to make up for any inaccurate AFR during cruise though - unless you force open loop.

tici

iTrader: (1)

Well, when the PCM is adding fuel (especially at high MAP) it means that the environment has changed in such a way that the engine needs more fuel.
So why it shouldn't need more fuel at WOT too?

SSpdDmon

iTrader: (10)

If everything were tuned equally from the factory, than this wouldn't be a problem. It's a problem because you've modded your car and the factory tune is no longer accurate. You could be rich at the MAP threshold just before PE kicks in and lean when you go WOT. My point was, a good tuner will eliminate the variables that keeps your tune from being consistent. Having positive fuel trims at WOT is one of those variables.

tici

iTrader: (1)

My WOT has been tuned on a day when the load LTFT were all very close to zero and cell 22 was = 0%. So I guess when the PCM is adding fuel allover the place (included cell 22) it's not too wrong. It's safe.
If the PCM is removing fuel allover the place WOT will be richer than necessary (than planned) but that will be safe too.

Differences are mostly depending on wheater, do you think a tuner can set up your car to be wheater-safe?