What is ECU tuning? Does it really work? An ECU tuning or an engine control unit tuning is also called remapping. It is done in order to adjust the settings of the car in order to bring out the best in terms of the performance of the car. This is done by overwriting the already existing settings that the car comes with so that the owner can readjust or re-program the car according to his or her needs. You may wonder how this remapping is done. It simply refers to the changing of the manufacturer's default settings of the car and adjusting it to the needs of the owner but within what is legally permitted. However, the effects of tuning can only be measured on the basis of how the owner uses the tuned car.