Running dohc on a sohc pcm?

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Dodge This One
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Running dohc on a sohc pcm?

Post by Dodge This One » Sun Apr 07, 2019 7:51 am

Hi all, no experience with this, so I figure I'll ask. I know a sohc can be ran fine off a dohc pcm. How about in reverse? I have a mostly built up dohc motor (stock cams) that was running fine on it's stock pcm, I just swapped from atx to mtx so I had it programmed into a psyched but failed smog. I'm trying to be cheap and not get a new cat right yet. I found a stock manual pcm but it is for sohc. Any issues to be foreseen? This will be a temporary thing. Or does someone have a 97-99 mtx ecu for dohc cheap?
Owned 3 1/2 neons to date, back down to the first one I started with.
99 ATX white coupe with dohc and lots o mods and a handful of trophies, more show than go.
97 purple plymouth ACR - sold, heard it is TORE up
03 SRT-4 front clip, cut into pieces, put into the trash can :)
95 coupe - given up on project, currently being parted out to my white neon or to ebay, coming to a recycling center near me soon.

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Re: Running dohc on a sohc pcm?

Post by NickKo » Mon Apr 15, 2019 1:33 pm

It won't be 'optimal', but it should run the engine.

- Nick
-1998 2-dr SOHC MTX= 52mm TB; Maddog STS
-1999 4-dr DOHC ATX= went to car heaven (junkyard)
-2000 Ply.LX with MTX = Maddog STS; CAI; R/T muffler + Header
-2001 Ddg.ES ATX = UDP, Magnum Header; + Syked PCM 'pending'

-1971 Ply.Scamp SL6cyl. ('Horse Traded' away)
-1968 Chry.300 w/440 V8 (sold)
"MoPar or No Car"

occasional demons
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Re: Running dohc on a sohc pcm?

Post by occasional demons » Tue Apr 16, 2019 10:35 am

Be sure you have a good o2 sensor, because the fuel trims at near/WOT are going to rely on that more than the programmed fuel curve.

I doubt it will run lean, as most '97 to '99 DOHC come with 21lb injectors vs 19 lb that the SOHC have. So the injectors are going to be compensating for a anything the SOHC does not put out. It is programmed around the 19 lb injectors. The o2 will probably be leaning it slightly from the program under most normal driving conditions.

If you run SOHC injectors, then there could be a slight chance of going slightly lean, if they couldn't deliver, but I doubt it, considering magnum heads with a hotter cam have been successfully run on 1gn 2.0's.

Like I've said before, putting a fresh o2 on my '01 with a 60mm TB made more throttle response than the UDP ever did. It was the best "mod" I ever did. :grin: That bigger opening will lean it out momentarily, until a tired o2 sensor catches up. The same principle would go for a better flowing DOHC head.
- Bill

desmodromic wrote:You have to remember what's important here, while they make New humans everyday, they'll never make another Neon.
Skellibert wrote: Fri Oct 13, 2017 3:42 amThis is a daily by the way, not a track car or fun buggy.

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