[rotorB]

Не прошло и 2х лет нашелся ответ.))

The fuel trim is the amount of fuel that your car is adding or subtracting to the fuel mixture in order to achieve the desired air fuel ratio. It does this by increasing or decreasing the injector pulse width. Our cars have 4 Fuel Trim values: Short Term, Long Term (idle), Long Term (cruise), Long Term (high). Fuel trim calculated during "closed loop" driving, when the car is using your O2 sensor to lock-in a AFR of exactly 14.7. However, it is applied during open loop driving, when the car is using your fuel tables, load, scaling, etc. to calculate the proper fueling based on your tune. For this reason, it's extremely important to have your fuel trims accurate, or your AFRs will be off by a significant margin when driving in open loop which will damage your motor. A properly tuned and running vehicle will show all of the long term values close as close zero as possible and certainly not more than +-5.