Thread: Long Term Fuel Trim

LTFT = long term fuel trim, adjustments to the base fuelling map to keep the readings to stoichometric according to the O2 sensors.

It probably means the gas needs a tune. It's the amount the fuel map has drifted from the petrol setting. The difference left to right at 3% is not large and many gas systems allow you to tune out a variation between banks. Injectors aren't super accurate and 3% is not much of a difference in flow rate. I've seen worse. Much worse. One el cheapo Chinese system I recently played with even had corrections available for each individual injector.

You could just be suffering a drop of regulator pressure, a slight crank up of the pressure adjuster screw may do enough so long as there aren't any other problems present. Mind you, even 17% LTFT isn't too much so long as its within the allowed variability in the petrol ECU, some ECU's will chuck up the check engine light for less, some not until its around 25%.