www.InstallUniversity.com - LS1 Edit Tuning

First Stop - Tuning Long Term Fuel Trims (LTFT)

After the "no brainer" functions have been programmed using LS1 Edit (i.e. trouble code deletions, fan temperatures, torque management, etc.) you will want to do a lot of logging to see where your Long Term Fuel Trims (LTFT) are. The common thought on LTFT at the present time (7.122002) says to have them from -1 to -8 range. Go about logging them by taking a 15 minute cruise where you do NOT make any wide-open-throttle (WOT) runs. Don't drive mono tone but don't try to qualify for any Top Fuel Eliminators either. Let the car come up to normal operating temperature and why not cruise around for a few minutes before logging.

A few questions come up at this time:

What do I use to log? - A scan tool of some kind, (Auto Tap or EFILiveV5) that will allow you to save the data and export it to MS Excel or equivalent program (Star Office for Linux users). I personally use both of the above (Auto Tap and EFILiveV5) because they use the same cable and have advantages to having both programs.
What parameters do I log? - This is only a recommendation but I log many parameters such as:

TP %, RPM, ADV, KNOCK, Speed mph, LTFT1, LTFT2, O211 mV, O221 mV, BPW1 ms, BPW2 ms, BLMCell, MAF gm/s, MAF, MAP kPa, ECT F, FSAB, IAT F

The LTFT need to be negative in order to have a consistent results with your tuning. When the LTFT's are positive at part throttle right before you go wide-open-throttle (WOT) the computer will dump extra fuel thinking your car is lean. Positive LTFT's mean the computer is adding fuel because it believes the car is lean and a negative LTFT means the car is rich and the PCM does not add the extra fuel during a WOT run. It is very apparent that you want to get them negative so you can take one more variable out of the tuning process. At this point there are several ways to tune your LTFT so they are negative at part throttle.

Scaling the Entire MAF Table by a Percentage

This is probably the most common method used by do-it-yourselfers using LS1Edit. You will just scale the entire MAF table by a percentage (i.e. 3%, 5%, 10%, etc.) until you bring your LTFT between negative (-2) and negative eight (-8).

This is fine for a lot of applications but why not go the extra mile and do a better job. I like having my LTFT around the same number and in the range of negative two (-2). Scaling the entire MAF table by a percentage will most likely not accomplish that goal.