Background
Hello!
I got into the Evo scene in 2007, at that time (at least in Australia) the car scene was pretty divided between Nissan’s and Subaru’s; I was pretty young, had just landed a new job and was looking for a bit of a toy… I took a peanut STI for a test drive and was pretty impressed, AWD seemed to be amazing; but between the car sales man almost trying to kill us and it just seemed like every man and his dog had an STI I went off the idea.
I dont recall how I ended up in a Mitsu dealership, but it didn’t take much time before I had a black Evo9 in my driveway… After getting a tactrix cable for messing with the tune it didn’t take too long for me to really become interested in how the ECU worked… I think I was probably trying to hunt down a knock issue or something, but you can say the rest is history.
What is an ECU Mod?
In modern(lol) cars everything is controlled by the Engine Control Unit (ECU, but it goes by other names like ECM, PCM, etc). The ECU is just a computer (dumber than the device your reading this one, but smarter than most toasters)… And just like any other computer it requires software to run through the logic (process inputs, make decisions and control outputs).
When you “tune” your car (by modifying maps) you are actually updating the software that runs the car; Most of the time this is adding (or removing fuel), increasing boost, or advancing the timing… However you can also update the actual logic of the ECU to make it do “new” things.
One of my first mods was “KnockCEL”, this basically instructed the ECU to check for KnockSUM (a Mitsubishi ECU term that denotes how much Knock the engine is producing (or at least the ECU is detecting) and then makes the Check Engine Light flash to alert the driver to a possible problem.