Wiring stock NA ecu to run as transmission controller only

[MuffinMan06]

I have a plan to use the stock ECU as a transmission controller and an MSP ecu to control everything else. I will get the NA ecu all of the inputs it needs to command the transmission and run the gauge cluster since it is a sportshift.

I will splice the inputs to the MSP ecu as well and attach all of the outputs (except transmission) to it.

do you think the stock ecu can command the transmission and gauge cluster if it has all of the inputs? I'm worried that it will freak out and stop working as a TCU.


don't worry about transmission durability. I am getting a valvebody from level10 and adding performance clutches per their instruction.

 

[jadycr]

i tried this, i never got the chance to attempt it but i put a lot of thought/work into it, i ended up manual swapping before i could start it but i think it would work

 

[MuffinMan06]

i tried this, i never got the chance to attempt it but i put a lot of thought/work into it, i ended up manual swapping before i could start it but i think it would work

I think even if the stock ecu is stuck in limp mode it will still run the transmission as normal. afaik the TCU is a separate module within the sportshift ECU

 

[MuffinMan06]

i tried this, i never got the chance to attempt it but i put a lot of thought/work into it, i ended up manual swapping before i could start it but i think it would work

do you have a diagram written down by any chance?

 

[jadycr]

i never made a diagram but i have it all in my head you’d need to share tps crank and cam coolant and of course all the transmission sensors and solenoids. also vss. the manual ecu wont need vss but it will need crank can tps coolant knock and o2. obdII would be a decision of which ecu you want to be showing codes. you could maybe use the transmission controller ecu as the emmisions as well and be able to let it control fuel purge, read o2, egr and the egr boost sensor. you would pretty much have the msp ecu get power crank cam tps coolant knock iac ground iat and o2 and it should run the engine just fine. the other ecu would see all of those inputs as well and just control the other half of things like transmission and emmisions. it would output injector pws and spark but you’d cut them and let the msp ecu control them. sorry for such a long unorganized and repetitive response im just waking up but thats about the jist of it

 

[jadycr]

I think even if the stock ecu is stuck in limp mode it will still run the transmission as normal. afaik the TCU is a separate module within the sportshift ECU

it will not run the transmission normally, i auto swapped a p5 from a manual and it gets stuck in 3rd if it doesn’t have enough inputs. my issue was speed sensor /some wiring goblins i tracked down. it was because we swapped an abs harness into a non abs car. you won’t have that issue

 

[jadycr]

in fact my friend who dailies it might still be having some issues with it shifting, i think he has to shift it into 2-1 then back to drive to get it to drive normal. i know you have the tiptronic so its definitely different but if you just don’t touch outputs on the stock ecu other than injectors spark and iac and keep everything else hooked up it wont know its not controlling anything. unless the o2 reads leaner or richer than its commanding it’ll maybe throw a code but it won’t stick the trans in 3rd.

 

[BenjiHoggi]

This is crazy but really cool. Not something I'd attempt, but as an engineer, it's very intriguing to me. I'll certainly be following to see how it goes!

My brother has an 03 tiptronic, it's definitely soft and spongy compared to my 03 5speed. Curious how it goes with a turbo