Piggyback Engine Management: This is an engine management option that works in conjunction with your stock ECU. Depending on the manufacturer, this solution works by the piggyback unit controlling some engine management functions and the stock ECU controlling others. This form of engine management is best suited for people who:
a. Will probably modify their vehicle frequently and require additional tuning
b. People with the ability to do their own tuning
c. People that live close to a tuner
d. People that want to get the maximum power and safety out of their car

It is important to mention that most piggyback units come with base maps. These base maps work very similar in function to a reflashed ECU whereas you can run the base map and be 100% fine, or when the day comes for someone to tune their own car or have it professionally tuned, they may do so.

Examples of Piggyback Engine Management are Unichip, Xede, UTEC, and others.

Stand Alone Engine Management: This is an engine management solution that totally replaces the stock ECU and controls 100% of the engine’s functions. This form of engine management is best suited for people who:
a. Will probably modify their vehicle frequently and require additional tuning
b. People with the ability to do their own tuning
c. People that live close to a tuner
d. People that want to get the maximum power and safety out of their car

This form of engine management is generally reserved for more advanced users and people going for really high levels of performance.

It is important to mention that most stand alone systems do come with base maps. Unlike the base maps that come on reflashed ECUs, these base maps are meant for your vehicle to run for a short period of time and are not meant to be used as a permanent solution as is the case with the other base maps as described above. Consider these base maps as merely as short term option until end user or a professional tuning.

Examples of stand alone engine management are MoTeC, Hydra, AEM, and others.