Hope that gets some attention. ;D My dilema is this. We have been logging on my brothers LT1 6.0 liter truck which has a stock motor in it right now. Normally he has a built motor putting out 320 or so HP and has a two stage 350 hp shot of nitrous. But like any motor putting out that kind of HP it is being worked on. The last run on the motor had made some pretty impressive S's out of about 6 of the rods.
Anyway...
The computer was programmed by someone for the modifications done to the built motor. A Wide Band O2 sensor is in the truck that monitors Air Fuel Ratio.
After logging for a while with the stock motor we found that LTFT's are pretty positive around 15 or so. The Wide Band O2 sensor shows as being perfect Air Fuel Ratio with just very minor fluctuations which is completely normal.
Now my question is this, if the computer is able to make these compensations to the fuel trims and there is 0 knock and performance seems normal for the stock motor and the logging is normal other then the elevated LTFT then why is it so important to have your LTFT set to slightly negative? BTW: The IFR tables in the computer are the same as a stock 5.3 liter image we were using to compare with. So the guy who programmed the computer must be making the changes to other settings. He supposidly used to work for GM doing actual programming to the computers. He does not use HP Tuners nor LS1 Edit and he apparently uses a hex editor and some other method of applying the image. The good thing is the computer is not locked and we were able to read the image just fine.
So again I ask why is it so important to have slightly negative numbers for the LTFT? ???