Has anyone ever????

[autopat]

Has anyone ever run a DOHC engine with the SOHC ECM? I don't see why it wouldn't work, the ECM would make the necessary changes if it were running lean, rich, or whatever, they both have MPFI, I might have to swap injectors though, I don't remember if the injectors are different or not. If the sensors are the same, it should work, but I figured I'd ask the experts before jumping off. I have a 96 SC1, and a spare twincam engine to rebuild out of a 95 SL2, I figured this would be a good time to upgrade, I also figured if I used the original SC1 ECM, the trans wouldn't freak out. Open to all suggestions but 1, NO, I do not want to change it over to a stick, if I do the wife won't drive it (not that she can't, but she won't).

Pat

[rc1488]

Has anyone ever run a DOHC engine with the SOHC ECM? I don't see why it wouldn't work, the ECM would make the necessary changes if it were running lean, rich, or whatever, they both have MPFI, I might have to swap injectors though, I don't remember if the injectors are different or not. If the sensors are the same, it should work, but I figured I'd ask the experts before jumping off. I have a 96 SC1, and a spare twincam engine to rebuild out of a 95 SL2, I figured this would be a good time to upgrade, I also figured if I used the original SC1 ECM, the trans wouldn't freak out. Open to all suggestions but 1, NO, I do not want to change it over to a stick, if I do the wife won't drive it (not that she can't, but she won't).

Pat


I dont think it will work. Lowsaturn will give you a definite answer tho. I dont think it will work bc of the different power bands of the engine. Yes all the sensor are the same, however mixtures are determined by tables in the PCM. The tables are quite different im sure between the two models. I think youll find your gas milage very low.

[Low Saturn]

The engine will run, but not properly. Why do a DOHC swap and have it run worse that a badly running SOHC by using the wrong PCM. Either do it right or dont do it at all.

[autopat]

The whole point in asking about this swap was to avoid the cost of unnecassary parts, but I guess I will get the fuel, and timing tables and compare them, and if worse comes to worse, I'll leave it alone. As far as the "do it right...." I'm the poster child for doing it right, or not doing it at all, but I was hoping for a resounding "Yes, they are the same" but that does not seem to be the case, I will check out the programs, and make the mods accordingly.

Thanks, Pat

[Low Saturn]

I will check out the programs, and make the mods accordingly. Thanks, Pat


Mods to the programming?

Physcially the PCM's are the same, but the difference is in programming. If you want to mess around with fuel tables and have full adjustability, you'll need an aftermarket engine management system and ditch the stock PCM. Otherwise, just pick up a stock DOHC PCM for a 1996 SC2, SW2 or SL2. They're pretty cheap. I just picked up one for my 1996 SC2 that I'm doing an auto to manual tranny swap to.

[autopat]

I would, but I don't have a spare DOHC trans, and I kinda like the lower gear ratio of the SOHC auto, but if I found a good working DOHC auto that someone had just lying around as a spare.... I probably would just swap it in, and avoid the pitfalls of the PCM programming all together. I did talk to Westers about the program though, he said he can program the PCM to work with SOHC auto, but of course it costs...it always costs... But I do have LS1edit, I haven't tried it on the Satty yet but it worked fine for my '02 pickup, and my wifes '04 Rendezvous, albeit, I didn't make any changes, just for looking around though.

Pat

[autopat]

Oops! I was perusing the instructions for my edit software, and it does not support any of GM's 4 banger's. Poop, back to the drawing board!

Pat

[Low Saturn]

Yeah, theres no hand held programmers that can edit the Saturn PCM. Unless you want to invest a few thousand dollars in a TEC-II.

[autopat]

I'm thinking I might shelve the whole swap, I'm fairly happy with the performance/mileage as is, besides it's just the DD. I guess I'll just rebuilt the twincam for the next Saturn I pick up. Thanks for the good info though!

Pat

[SCDYNE]

I would, but I don't have a spare DOHC trans, and I kinda like the lower gear ratio of the SOHC auto, but if I found a good working DOHC auto that someone had just lying around as a spare.... I probably would just swap it in, and avoid the pitfalls of the PCM programming all together. I did talk to Westers about the program though, he said he can program the PCM to work with SOHC auto, but of course it costs...it always costs... But I do have LS1edit, I haven't tried it on the Satty yet but it worked fine for my '02 pickup, and my wifes '04 Rendezvous, albeit, I didn't make any changes, just for looking around though.

Pat

There is limited support for the 1991-1995 PCM from LS1 Edit and also limited support of the 1997-2003 ECU from LS2 Edit.(Probably what you have) If you wanted to get a hold of the bootloader for the 1997-2002 ECU Westers has it (so I hear) as does Vector Motorsports. Digital Horsepower Inc also had it, but they may or may not have gone out of business. You can get the cal from the ECU with a limited amount of effort, but getting it back in requires the bootloader. Not likely Vector would offer you anything other than a modified ECU, but if you wanted to upgrade to a 1997 ECU, harness and DOHC they would be the first place to go for options.

[tarsun]

i have done that.... i did "the swap" and when i was done i was given the wrong pcm and i had the soch pcm so i put it in and IT RAN. but not well.

i would NOT do it JUST to DO IT.......

but if you NEED to you can run on it for a LITTLE while

[92SL1Mann]

maybe just find the right PCM in the wreckers? cant be that much

[virnin]

maybe just find the right PCM in the wreckers? cant be that much

There is no "right" PCM for a DOHC with an MP6. That combination wasn't offered from the factory, only SOHC/MP6 or DOHC/MP7.

For the OP, I think you would need to use the injectors from the '96 because the '95 would have low impedance and the '96 would have high impedance.

[Dreamimage]

A SOHC PCM will work with a DOHC engine, but you really shouldn't drive it like that for very long.

I had my DOHC engine running with a SOHC PCM, I didn't drive it tho. But I let it run with the SOHC PCM, then shut the car off. I then installed the DOHC PCM, and turn on the car. Immediately, I could head a difference in the tone and response that the engine was receiving.

Also, keep in mind, that when you are swapping in a DOHC PCM to replace a SOHC PCM, you have to sand down the guide pins on the adapter plugs in order for plugs to fit in their rightful spot. The guide pins are reverse on a DOHC than on a SOHC (which happened to me, thankfully I had some sandpaper laying around).