Wondering if there were ever any "true" dual exhaust applications on any 90s Magnum vehicles with OBDI or OBDII. I'm figuring there were not.

Has anyone heard of any PCM or aftermarket PCM that can handle true dual exhaust?

I'm figuring there would have to be two (or four depending on the year) seperate O2 sensor readings for it to work correctly. Reading from one side only would probably not give it accurate info.

I'd be looking at doing this in MA which is fairly strict on emissions inspections so it would have to be close to a stock type application, cats and all.

Off hand I'm guessing that what I'm looking for doesn't exist in any factory applications and might not even be available aftermarket unless I get into some kind of really fancy and expensive custom rewriting ofthe PCM.

Any ideas out there?

 

I don't think anyones actually had to have their PCM flashed because they ran dual exhaust. But I could be wrong.

 

I don't think that was ever done on the second gens as a stock application. As far as running 4O2 sensors, the California trucks do that, but I don't know if it would work for the specific application you're looking for.You will need 2 cats and 2 mufflers to keep it "stock" for emissions (I'm pretty sure Mass is one of the more picky states), but if you run anH pipe or Xpipe right before the cat, youmight get away with 1 pre-cat O2 sensor if you install it in the H or X. As far as post-cat, you could probablyrun in one side and not worry about the other, or run another H orX pipe on the post cat side as well andinstall the O2 sensor there.

 

Yes, MA is a pain in the neck when it comes to that stuff. I wanted to try and keep it emissions legal if possible or at least arrange something that could pass. Same type of thing on my planned 5spd swap. From what I understand it would fail if it had active codes from the PCM looking for the auto trans and they can't overrule the machine and say "those codes don't matter because it has a manual trans now"
I plan to use the 5.9 5spd Ram PCM for that swap but that's a whole different project.

On the true dual thing, my thought is: If I run the sensors on one side only and it's looking forthe normal mixture from a V8 then it's going to detect a (false) lean condition and try to throw too much fuel at it to make itself happy, and it will never find the readings it's looking for so it won't be happy.

The H pipe idea is a great one! Hadn't thought of that. That leaves the problem with the second sensor though.
Although, I think the second sensor is only on OBDII vehicles if I'm not mistaken, so it seems like the H pipe idea would be do-able on an OBDI vehicle but probably a lot harder to work out on an OBDII vehicle.

This could work out though since the project I had in mind was aimed at my 93 5.2 Grand Cherokee LTD. I've been seeing fuel injection manifolds and systems for big block motors from Edelbrock and F&B Performance Engineered Products (a Six-Pack manifold!) I'm guessing those are stand alone systems designed for pre-emissions inspection era cars but I'm thinking they might be able to tie into an existing EFI setup. I haven't studied up on them yet but it looks like they use most of the same type of inputs as a stock system with the possible exception of cam position sensors in the distributor, intake manifold temp sensors and maybe O2 sensors. They might even use those too. I'll have to look into that when I have more time.

B&G performance should be open today, I'll see if they've ever done anything along the lines of a dual exhaust "conversion" or rewrite on a PCM.
Maybe it would work if they rewrote it so the O2 sensors are only looking for half what they normally look for. I suppose if I had to use a single exhaust system to make it work it would still be worthwhile, it would just have to be some BIG pipes! Might be better sticking with a single pipe anyway as there is almost no room in the 4WD ZJs for dual exhaust and I don't think I'd want to convert to 2WD just to do this swap. (it's not an offroad build though)

Now, as far as whether the big block will fit in the ZJ, that's a whole 'nother matter. I've seen at least one company that makes motor mounts for big block Daks/Rams.That's a start. It would be extremely tight for sure and it would probably be a lot easier to use a B motor as opposed to an RB motor since the RBs are about 1 1/2" wider IIRC.
My 93 has 207K miles on it and it is in "less than mint" condition so I wouldn't be afraid to do a bit of cutting if I had to.

So, that leaves reading up on the Edelbrock and F&B systems and maybe talking to B&G Performance about their flashes and re-writes. I'll post back when I get some info - John