Originally Posted by intenseblu
its not a piggy back thats how ... a auxillary injector controller functions fully apart from the main computer ... thats the secret ... the stock computer operates its stock function unknowing that the auxillary unit is peeping at the TPS values and firing another injector.
been there done that ... built a 8 injector system for a 2.0 DOHC i built a system based around a T3 super 60 ... all custom hand work in my spare time from sourcing the exhaust manifold from a mexican production vehicle (no emissions laws meant they had beastly engines when we were getting crap in the late 90s) to build the auxillary controller, 8 injector manifold, blah blah blah ....
and just like back then all you have to do if the stock ECU wiggs out when it sees boost is clamp the signal the MAF/MAP sees ... so you wire up a probe to the signal wires to check voltage and rip on the car when it is NA ... record the max voltages it sees then use a potentiometer (POT/variable resistor) to "clamp" the signal.
it works like a charm and the car drives like stock out of boost.
I understand your ideas, and the theroy, but I have sneaking suspicion the motronic ecu is smarter than we think. otherwise why haven't other latemodel Benz tuners tried this. Maybe it's not that difficult to modify the fuel/timing with a 7th injector, I know Woody posted on his site the Mega Squirt running his car at idle, but that's all Ive seen so far.
If the ecu is seeing more fuel in the exhaust stream for a givien mapp cell, what is it going to do when this occurs? Will the computer open the throttle more to compensate, and thus causing you to accelerate more? or is the TBWire a separate function all together.?
When will you put together a system to prove your theory? we would all love to see a running system that is safe and reliable.
I do like the idea of being able to use the srt6 ecu myself, it seems like a better option and there are already mapps available for the srt6.
either way it's going to happen soon or later its just a matter of time.