I was digging around taking inventory on my parts and stumbled upon an idea. Maybe a crazy idea...

What if you were to port match and re-drill a 13b LIM (Seems pretty easy) and install the s4 UIM, dynamic chamber, TB, elbow, intake etc on the 12a motor... Then use the 650cc GSL-SE injectors and ECU to run it all.

Would it work?

I have most of these parts laying around. The 13b does not have that much more displacement than a 12a so it should work right? Has anyone tried it before?

 

That actually seems doable. The GSL-SE computer only handles fuel so spark would still be controlled by your dizzy.

 

Just rebuild a 12a with 13b se plates. Then get the lim mani modified so the 5th and 6th ports are functions. lastly, add the se computer.

 

I actually had this idea a while back too.

In theory, the RB sidedraft LIM for the 12A should allow you to bolt the GSL-SE upper onto the 12A.
I would agree that using the -SE center iron for the injectors is a good idea as well.

As for a 6-port 12A with 13B manifold, thats not gonna happen...

 

Do you think the engine would run well with just the secondary injectors wired as primaries on the s4 UIM? The GSL-SE injectors are in the same location as the s4+ primaries correct? It may react differently being that the injectors would be in a different location.

And to the post regarding the 13b center irons... I don't think that would help because the 13b LIM is still ported differently. You would have to swap the front and rear irons as well.

 

Interesting Idea guys, also just to dig up old memories and such floating around on the other rotaries forum a long while back was some one with a similar idea, I think the user was "Jeff20b" he was doing something a little different but I suggest you look up his ideas, because you will find that Mazda did have a 6 port 12a that was a JDM engine, now it was carb'd but I think you might be able to use the part of the intake manifold to assist you in what you are doing. It is a near absolute fact though that you are going to have to rebuild the engine using the center housing from a 6 port GSL-SE engine so you get the injector ports

Good luck

DAVE

 

Regardless of the 4 port or 6 ports irons on a 12A, the 13B intake is wider so you will have to use an adapter anyway. I think the best route would be to use the RB lower intake, and use the S4 upper with the GSL-SE injectors. If you think about it, using a side draft pulls the fuel in at the top of the intake. So having the injectors higher up the intake stream isn't really going to matter that much. Just look at the TweakIt throttle bodies.

 

The problem with using an RB lower manifold is that it isn't straight. What I mean by that is that if you were to bolt on an upper manifold, the manifold would actually point backwards towards the firewall a little bit. It's quite annoying looking but would probably physically work. You will need to fab up a location for the fuel injectors though as the GSL-SE only has 2 and they are on the intermediate housing.

You'll have to find a way to regulate fuel flow. You really need to be able to tune it somehow. As was pointed out already, ignition isn't an issue with a distributer. However since port timing is so different between 12A engines and 6 port 13B's, even just accounting for airflow differences with smaller injectors isn't going to work very well. In the end it'll be alot of trouble and probably won't make the power it does stock. If you just want to use the GSL-SE manifold I'd recommend using some form of standalone. If on a budget try a Megasquirt. They just aren't hard to use. The problem with them is that too many people but them without learning anything about efi systems. If you're going to change manifolds anyways, use a 2nd gen one so at least you have fuel injector locations to use.

 

I have a spare 2nd gen LIM. If you bore out the lower center mounting holes it will mate up. There is just one problem area on the front of the engine where there is about 4-5mm of intake leak, lol. I was thinking about port matching everywhere that it is slightly off. Then I planned on making a thin adapter plate to fix the overhang problem on the front. THEN I would re-drill the rest of the bolt holes on the manifold. I know it would mate up fine after that.

I would just think the problem you'd run into would be running rich and a lengthier fuel travel time.