The problem with Lancer's is the ECU, they do not go into open loop of their own volition. This is a very big problem when you are trying to tune a vehicle with a dynamic ECU. The ECU will continuously learn and correct out your settings in many cases. There is absolutely no harm in doing the above. As Andrew said it is also quite reversible. SAFC is a "good" fuel computer yet cannot achieve the addition and subtraction necessary for tuning because of the ECU in Lancer's. Additionally this idea has already been tried and worked quite well.

So understand the overall concept and what kind of ECU you are dealing with and move past the basics "before you post"

 

And for the record I just browsed through the entire AEM EFI basics document, and will read the entire book/document by the end of today. But I can already tell you it doesn't address dealing with dynamic ECU's and running a fuel computer (which is what we are discussing here). It does a great job to explain how to size injectors and fuel pumps and fuel delivery systems. Which is wonderful, and great information. but keep in mind that the AEM EMSystem is a standalone, and is a far cry as far as issues and often function are concerned relative to a dynamic stock ECU.

 

I read the entirety of the AEM EFI basics V1.3 document. While a good read, it is by no means a basis for knowledge in tuning. Frankly if you didn't know pretty much everything in that documet already you don't have any business trying to run a piggyback let alone a standalone system on your own.

And for the record regarding the topic at hand. I am a mechanical engineer with an emphasis in mechatronics and control systems. In fact I am currently employed as an Electrical engineer maintaining and redesigning closed loop control systems. Every single day I work with control systems and electronics to deal with input and output and system performance. So I have just a tiny little idea as to how computer controlled systems work and what is good and bad to do with them.

Additionally if you really think that sending the system into open loop is a bad idea then explain to me why many car manufacturers (Mazda is one example) send their computer system into open loop at WOT?

Anyway... moving on...