Some "strange" conversion questions..

[Paul_VR6]

As you may know I'm new around here, and new to the LS1 world as well. I've been reading old posts on the forums trying to learn as much as I can, but there's still a few things that I can't make sense of and I'm hoping you guys can help. It seems that you all know your stuff and hopefully my simple questions are worth your time answering!

Anyway, I'm looking to do a LQ4/4L80E conversion to my 88 1500 Pickup. What I need is info on how the stock harness and management are configured on the donor vehicle.

I don't know much about the GM trucks (learning&#33 but I need to know if the computer and harness that controls the auto is one and the same as the one that does engine management. The reason I ask is that I'm planning to do standalone fuel/spark management on the engine, and just want to retain the stock computer on the trans.

I know there are standalone trans harness and programmable computer combos, but those are WAY out of the ballpark once I plunk down the money on the motor/trans. So I need to know what I'll need to keep to run the stock trans computer without the engine computer. That is, if that's at all possible.

Also, are there any signals shared by both computers (there are two right??) like TPS, or MAF signals?

Thanks in advance for the help!!

[97 SS 383]

The computer that controls the engine also controls the transmission. It does this in the same harness, and it does this using signals such as throttle position, vehicle speed, and I am sure a few others.
You would probably be better of just using the engine computer to run the engine and tranny, and save some headache. Why spend the money on a seperate ECM?

[Paul_VR6]

Thanks for the input! Any idea if there's anything that needs to be done to the ECM to make it happy NOT running the motor functions and removing those items from the harness?

Again thanks for the help!!

[97 SS 383]

I have no idea. That is not anything I have ever known anyone to do, and I wouldn't guarantee anything without testing it myself first.
I would guess if the ECM gets all of the powers and grounds, as well as the VSS signal and TPS... it might work.
What's wrong with having the actual LS1 computer running the engine?

[Paul_VR6]

Why bother using the LS1 computer when you have standalone ready to go on it anyway? Probably easier and cheaper then getting custom programming done for whatever I may do to the thing.

[97 SS 383]

Yes... easier... it deffinately looks like it should be easier... If the transmission works.
By the way.. what stand alone ECM are you planning on using? I didn't know anyone other than GM made something compatible to the LS1 engine.

[Paul_VR6]

I'm planning on using Megasquirt. I've built four of them now, and installed two on buddy's cars. Got a 454'd 87 Silverado running on it now, and lets just say it runs way better then the carb'd 350 ever did, and better mileage too.

I don't see how it wouldn't be adaptable to the LS1 though.. all I need to do is make a crank trigger, and use the stock TPS, coolant and air temp sensors then find out where to grab a vacuum signal. Not too hard to do.

[97 SS 383]

And what will you do about making all 8 coils fire correctly?
You do realize there are 8 coils and no distributor right?
and from looking at the "Megasquirt" website, they don't seem to address using this system with a SFI multi-coil system. The newst GM sample vehicle looks like a 91 Caprice.

[Paul_VR6]

Unless UltraMegasquirt comes out, I'll be using a Ford 36-1 trigger wheel and EDIS ignition module with the MS ECU. The EDIS is compatible with coil on plug just like the LS1, as long as the coil impedance is high enough (which it probably is). I know, Ford parts on a Chevy, but at least I know it'll work

I'm installing another MS on my VW soon setup in the same way, so I'll know for sure if it's worth hassling with or not.