Scooter

what if u disconnect the battery and reset the fuel mappings just prior to racing to where the ECU has no prior driving style??? will the settings b automatically configured for max performance from the start and then work down from there??? or u think it's the opposite??

Nashua_Night_Hawk

The best... have 3 1/4 miles runs at WOT and you got the best fuel/timings maps, period!

The best for CLS is back-to-back 1/4 mile runs.... I saw a drop of at least 0.35 sec!

spiroh

I went to the track one time, and did a couple of runs. Then I reset the ECU, and my MPH and 1/4 times were not as good as before. After a couple more runs though they did get back to normal.

spiro

scalbert

It really depends on how the car is running and does it need to adjust the trim values.

Say if for some reason you are running rich and the short and long FT values have corrected this, by resetting the ECU you would be back at the rich running which could hurt your times. On the other side there could be the opposite effect.

However, the car should be running fine to begin with and resetting the ECU would do nothing. If the trim values are at 0% to begin with, resetting the ECU would do nothing other than keep them at 0%.

One other thing to keep in mind, the STFT will adjust within minutes with the LTFT following shortly. So if you are staging and at idle for about 5 minutes or longer the trim values will have gone back to their previous state.

Scooter

wait...u're losing me on the acronyms

FT means...
STFT means...
LTFT means...

sorry, im just stupid like that

fbazakos

No, you're just not an engineer

FT = Fuel Trim
STFT = Short Term FT
LTFT = Long Term FT

fbazakos

Here this will help:

http://www.rs4.org/quattro/technical...agnostics.html

scalbert

heheh, too many acronyms...

Just to add a bit, the STFT is what immediately reacts to the current A/F ratio. If at idle or part throttle the PCM detects rich or lean conditions, it will start adjusting the STFT until the AF ratio gets back to normal. If does this in percentages points which equates to adjustments in injector pulse widths.

Once the STFT gets the AF ratio back to normal the PCM starts adjusting the LTFT and shifting the STFT in accordance.

So if something occurs to change the AF ratio at idle or part throttle the PCM first gets the STFT moving immediately and then adjusts the LTFT to bring the STFT to near zero. But cumulatively the combined ratios offset the injector pulse width.

This all happens immediately and can be watched with a scan tool.