5.2 to 5.9 magnum swap PCM/ECU compatibility

[clapped2gAZ]

Hello all, since you guys helped me out so much last time thought I'd bounce a question off ya. Apologies if this is the wrong thread, if it is ill go ahead and delete it

Long story short, I had a cammed and dyno tuned 5.2 magnum I built recently.
She spun the #7 rod bearing (clearance too tight, first motor build learned the hard way). Bought and am in the process of rebuilding a 5.9 magnum, using same cam, heads, ported kegger, ported throttle body and shorty headers, stock injectors.

Will the PCM adapt itself after the O2 sensors warm up and switch into closed loop? Tuner said it *should* be fine but im running Hypereutectic pistons and im terrified of detonation and lean conditions ruining a fresh motor.

I will be running a AEM 30-0334 wideband to monitor the AFR ratio, so I will have more reliable info to share once I get her running.

Sorry if that's a stupid question, very new to the tuning world, thanks!

 

[MadScientistMat]

Should start and run, won't be ideal. Were you tuning the PCM itself, and if so, with what tools?

 

[TT5.9mag]

If you have a tuner, and it can be tuned, it won’t matter what pcm you use. Any jtec will run it. Who’s tuning it and what software are they using?

 

[clapped2gAZ]

Learning the basics with HP tuners right now

 

[clapped2gAZ]

If you have a tuner, and it can be tuned, it won’t matter what pcm you use. Any jtec will run it. Who’s tuning it and what software are they using?

Original went with XACT dyno in tempe AZ but it made under stock horsepower. Dunno if he's just not great with dodge or i screwed up the motor in the build process. Going to try VooDoo performance in chandler next. I believe they will be using HP

 

[67Dart273]

The thing is you don't have a stock anything anymore. There is no reason EITHER computer will run the engine without tuning. I'd say One shot, the other shot, you have an equal shot with either

 

[TT5.9mag]

Original went with XACT dyno in tempe AZ but it made under stock horsepower. Dunno if he's just not great with dodge or i screwed up the motor in the build process. Going to try VooDoo performance in chandler next. I believe they will be using HP

If you’re not happy with either of those two, contact Ryan at Flyin' Ryan Performance | Tomball TX
He’ll definitely get you squared away and he does email tunes. Super nice guy.

 

[TT5.9mag]

Learning the basics with HP tuners right now

That’s funny. The two words “basics” and “HP Tuners” have never been in the same sentence before together. Ever.

I’ve tuned with hp tuners for 15 years now on my own junk and still only know 10% of what’s going on.

 

[TT5.9mag]

The thing is you don't have a stock anything anymore. There is no reason EITHER computer will run the engine without tuning. I'd say One shot, the other shot, you have an equal shot with either

a stock jtec ecu will adapt slightly to some improvements. Ported heads and a small cam and it’ll be fine with a stock ecu. At least enough to drive around. Tuning it is definitely recommended.

 

[MadScientistMat]

That's a tuner name I recognize... Let's just say I don't think you made a mistake building the motor.

 

[TT5.9mag]

That's a tuner name I recognize... Let's just say I don't think you made a mistake building the motor.

Can you elaborate please.

 

[autopar3000]

Like others have said, the stock 5.2 PCM will run the 5.9, but it won't be ideal. As long as the cam isn't too rowdy, the stock PCM will figure out the fueling needs and make sure it stays stoichiometric. The issue will be with the ignition timing. The stock 5.9 is obviously 42 cid bigger and it has a smaller cam than the 5.2 (probably). It can make small adjustments but it wouldn't know how to properly deal with the extra inches and smaller cam, so you'll be leaving power on the table.

Since your PCM is tuned already, it's hard to be sure exactly how it will run. But as for tuning it, +1 on Flyin' Ryan. I have never used his services, but I haven't ever heard anyone complain about the tune he provides. His understanding of the EFI Magnum is so dialed in you can tell him you setup and ship him your PCM. He'll tune it accordingly and send it back to you. But since you have an HP you can go with the email tune.

 

[MadScientistMat]

I've had to straighten out far too many avoidable tubing issues that have happened in that particular shop. If a car left there not making the sort of power it should, the first thing I would suspect is an improperly tuned timing map instead of a mechanical problem.

 

[TT5.9mag]

I've had to straighten out far too many avoidable tubing issues that have happened in that particular shop. If a car left there not making the sort of power it should, the first thing I would suspect is an improperly tuned timing map instead of a mechanical problem.

Yea I figured something like that but there are three different facilities mentioned and no one has a clue which one you’re saying to avoid.

 

[MadScientistMat]

Sorry. The one I recommend avoiding is Xact.

 

[TT5.9mag]

Sorry. The one I recommend avoiding is Xact.

Appreciate that.