Using Factory ECU for ignition only...
 

The ignition half of my MT LTX8 fried for an unknown reason a few days ago.

I am trying to get it fixed, but I am probably going to need to order a new circuit board from MT and in the mean time I want to be able to drive my daily driver.

The reason I need help is that I want to use my old stock ecu for ignition only and keep the mt for fuel management. I have an old NA ecu for an s4 and a hacked up harness for it.

I tried hooking up the tps, cas, a couple grounds and power wires and some stock coil packs, but cannot get spark. I was wondering if any of the stock or Rtek gurus could tell me which wires need to be connected in order to get the factory ignition half of the ecu to function. I am getting 12v and 5v on some ecu outputs, so it is at least partially powered on. I wont be running boost on this so as long as I get some advance with RPMs I will be happy. I would probably be happy just to see a spark! Any help would be greatly appreciated. BTW I have the factory wiring diagrams. I am just thinking I might be missing a needed sensor or ground or something.

Hmm.. Thats a pretty good question. Seems like it would work, but I am trying to figure out what you might have missed..

i think your missing a ground soemwere, i had that problem once when i had a carb and the grounds that goes in the engine block i forgot to conected and i didnt got any spark at all and i couldnt figure out until i tried them and got spark. i dont know if thats your problem but if your still dont work , get a first gen dizzy and use the trailing coils and wired them up and it will work.

Megasquirt guys run off the stock ECU for ignition a lot actually. Maybe you need to look in that forum.

Yep, go ask in the megasquirt forum. I know that they used to use the stock ecu for ignition before they got it running with the MS.

I might do that then. I will also look for more grounds that need to be connected. Thanks

I cant figure it out. Maybe it needs an AFM or something. Could I jumper the 5v ecu signal to the tps, boost sensor, afm and anything else to simulate a signal???? that would make testing a lot easier, and wouldnt the computer just interperet it as a maxed out sensor (full tps load, max boost, ect)?

the map sensor on my microtech lt-8s is reading 1psi off of what it should, i sent them an e-mail they said repairs would be free.
send tech an e-mail
http://microtechefi.com/

How does the Leading coil/ignitor pack work? It has the signal from the ecu, and a BW power wire going to it. Dont the ignitors need to ground out the other side of the coil somehow? So does the body need to be grounded or what?

im gonna make a sugestion, if your using it for ignition, just use a 1st gen distributor and use the 2 gen trailing coils. wiring is simple, you can still your microtech. if you need help install it let me knowill show you how. but if you search on the forum theres should be diagram of how to install a 1st gen dizzy on a 2 gen

The coil/ignitors have to have a ground and that ground is thru the base of the coil assy. It HAS to be bolted to the chassis and the chassis has to be grounded.

The stock ECU can do the ignition but the timing will be wrong in my opinion BECAUSE the afm on a stock car effects the timing advance along with the boost/pressure sensor also. No afm.....wrong timing. But the car/engine will run and be driveable imho til you fix your whatever.

For the record, all it takes is 3 CAS wires, power, gnd, and the ign signal wires. The car is running on the factory ECU for ignition and mt for fuel. I ordered new components for my MT and am going to fix it once they get here.

I could not use a dizzy because the MT needs a CAS signal to determine RPM.

The factory ecu does not need TPS or MAP or AFM to run, but I am sure everyone is correct in saying that these will affect advance. Right now I can tell you that it advances to a little over 15* BTDC when I rev it past 3k or so.

I am not planning to use this ecu for anything more than break-in. I may attatch a factory boost sensor and hook up the TPS to get more accurate timing.

In fact, my trailing plugs are not even firing right now. I have them hooked up but cannot figure out why they wont work. My egts are higher than before, possibly because of an incomplete fuel burn--who knows. They are not affected by advance/retard or adjusting the fuel mixture...which is weird.

Anyways I am going to most likely just run it as is until I fix the microtech....which has actually turned out to be rather easy. The replacement parts I need were available from a bunch of online electronics suppliers.

Thanks for all the help tho everyone!