I've been researching what all is required to install megasquirt, and so far the only real advantage I see over tuning the GM ECM is the ability to easily set up distributorless ignition, using a ford EDIS ignition module. It is not coil-on-plug, but uses coil packs, 4 of them for an 8 cylinder engine. It uses the 'wasted spark' method, which means that 2 plugs fire at once. This method does not need a cam position sensor, only a crank position sensor. I know I could add a crank position sensor without too much trouble, but I'm wondering how hard it would be to make the factory ECM control the EDIS module. It has 2 data wires, one for the ECM tach input, and one for the ECM advance control. The tach signal is a +5V squarewave, and the advance from the ECM is a +12V squarewave. I'm not sure how a GM ECM tells the ignition module to advance timing, is this even close? Most of the EDIS info I have found here:
http://www.megamanual.com/ms2/EDIS.htm

If this isn't feasible, are there any aftermarket options for something like this? I found a little bit of info on modifying an optispark setup and using an LT1 ecm, with LS1 coils, but that sounds like more trouble than it's worth.

 

Have you looked into the megajolt setup?

http://www.autosportlabs.net/index.p..._Users_Welcome

It allows 3 diminsional timing programming and works with the EDIS. You would have to keep the opti in place to simply provide ref to the stock ECM.

You would have full tunability and it would work with the stock ECM.

 

I was thinking of a TPI ECM though, not LT1. I don't think I could put an opti on a gen I motor without significant mods, right?

 

Though I suppose it would be possible if you had your own machine shop and an unlimited budget. But, the Opti isn't worth the hassle.

A TPI ECM would work with the Megajolt just fine.