Hello all,
can anyone gimme a proper explanation about how a piggy back ecu work !?

basically, it goes between all the sensors and the ECU and intercepts/hijacks and modifies the signal
making the ECU think the things are going on different than they are and therefore using it to force
ECU to send out different values to other components.

it can go the other way too, piggyback ECU getting the car ECU's triggers for injection and ignition
and then generating a modified signal based on the original data, for instance to offset ignition
timing and/or increase fuel injection pulse duration etc.

one of the most commonly used piggyback ECU's is Dastek Unichip.

hope this helps?

Thanks Cybernck - But is it manageable.. like an e-manage . mean controlling the values with laptop..setting parameter etc. ?