Log results, now what?

[ALK]

07 A6 C6, Drove 22 miles at constant 50-55 mph, 2000 rpm in 4th gear (auto), after a few cleanout punches, no retard. LTFT's 3.91 and 2.34. What do I have, rich, lean? What do I need to do? Come in Mike, Monte.

[ALK]

Forgot to mention car has Honker CAI and Magnaflow Maganapak exhaust.

[mikel]

If those are positive LTFTs, then go ahead and try a -3 setting on the injector slope, and try again.

Thanks

[ALK]

They are positive LTFTs. Do they mean I'am rich or lean at present?

[jsk06c6]

neither, the vehicle is staying at 14.7 AFR. But it is adding gas, so you want to zero that out (actually around -1 to -2 is suppose to be best) and let the STFT to keep it at 14.7.

[ALK]

If its having to add gas, doesn't this mean the engine is running lean at present? By zeroing out, aren't I adding more fuel? This is confusing!

[mikel]

No, it is adding fuel to get you to a constant 14.7: AF at cruise.
You want to get it to where it is not adding fuel to achieve the desired A/F ratio.

Thanks

[ALK]

Alright, if the ecm is having to add fuel to get 14.7 AF at cruise and I take this ability away. Want it be running lean? Whats going to adjust fuel then? Still CONFUSED!

[CANUCKPREDATOR]

Just trust these guys, they know what they are talking about. Don't try to over think it, just trust them.

[jsk06c6]

The LTFT's are a ballpark value for the computer to get you at 14.7 AFR in closed loop mode. The computer though will correct that via the STFT's based upon feedback from the sensors (O2 etc). The LTFT's apparently can slightly modify fuel at WOT, but only if the LTFT's were positive, hence why you want them slightly negative.

Your not really changing the LTFT's though in this adjustment, your changing the pulse width of the injectors, by adjusting the slope, basically your modifying how much fuel the injectors deliver, so that the value the LTFT's were adjusting is now done by the injector pulse instead.

BTW, 14.7 AFR is lean, its made for fuel economy. There are some vehicles that go all the way to 16.2 AFR in a special economy mode. It's not bad in closed loop, but either would blow up a motor at WOT.