I have recently had a question about the different styles of ECU's and tuning methods, so I thought I might post my answer for anyone else who may be curious with the same question.

These are my personal opinions, so some refinement may be necessary. Feedback welcome. Leah


Custom Flash Tune
Involves reading original tune from the ECU (computer) then modifying parts of the tune to correct the tune for aftermarket modifications and enhance the vehicle's driveability and performance. There is no physical modification to the ECU hardware, it's moreso like a software upgrade. The tuning process involves making incremental changes to the tune then flashing this back into the standard ECU and testing on a dyno (ideally). Once the tuner is satisfied that the optimal tune has been created, the final tune is flashed into the standard ECU. It is called Flash Tune as this is the method used to upload the tune into the ECU. As this offers full control over the factory ECU, areas like rev and speed limits, idle control, throttle control, torque clips, etc. can be modified for greater results in driveability.

Plug'n'Play
Is normally a term used for the style of installation of a piggy back ECU. It involves no permanent modification to the vehicle as part of the install, hence the product installation can easily be reversed.

Piggy back ECU
Also known as an Interceptor, is a system that works in tandem with the standard ECU (computer). It is normally installed on a vehicle that cannot be chipped or Flash Tuned, as the next best thing. It generates changes in fueling and ignition timing by changing the factory ECU’s load and crank reference input signals, to trick the ECU into behaving differently, to produce a tuned result. This system is limited in its control and normally cannot alter rev or speed limits, idle characteristics, etc.

Chip
Term used when an internal hardware modification is carried out on the the standard ECU to allow reprogramming of the factory ECU. More common in older cars. This is also still used as a general term for a modified ECU, even if it may more accurately be a Flash Tune or other.

Aftermarket ECU
Is a system to replace the original factory ECU, to control an EFI engine's sensors and allow a dyno tuner to refine the tune. This is normally applied to a vehicle that has extreme enhancements that max out the control available within the factory ECU and engine sensors, most commonly but not limited to the Air Flow Meter Sensor. Most vehicle's require an aftermarket ECU when the Air Flow Meter is deleted from the EFI system. It is best to stick to the use of the original standard ECU for as long as possible as aftermarket ECU's will not provide as much driveability and economy as the standard ECU.