I was doing some more work on my 85 RX7 over the weekend and spotted some significant oil leaks to go along with my coolant leaks too. So it looks like I'm going to slap the S5 NA 13B in there until I can get the 12A rebuilt.

Any tips I should take into consideration when doing this? I have the S5 engine, transmission, oil cooler, wiring, ECU, coils, etc. I want to run the S5 injection if possible.

I have heard swapping the front cover over so I can use the FB mounts, should I swap in the S5 transmission too?

I've completed a lot of swaps in the past (Mainly bigger Mazda engines into Fazdas (KLDE Ford Aspire, BP Ford Aspire, etc... 2.5L Turbo into a Dodge Shadow)) so it shouldn't be too bad, plus I have some fabrication equipment handy if needed.

I appreciate any help that will make this go smoother. I've been looking forward to running the FB more this summer.

 

You will need a GSL-SE front cover and oil pan. I used my FB transmission with a Turbo II engine and it worked well.

If you go through all this hassle, why would you rebuild the 12a that you cannot get parts for anymore? The 13b is such a better setup!

 

I've priced out the oil pan and the front mount bracket (Racing Beat) but if I use the 12a front cover will that plate work just fine?

How did you get the S5 OMP to work? Is there a good how to? I heard mention of making a rod to lift it at heavy throttle.

 

I think I'm going to just make some brackets to use the S5 mounting locations so I don't have to mess with the engine much.

 

You have to use a GSL-SE front cover and front mount if you do it that way. That also makes the cleanest and simplest swap. I found all of the needed items on here years ago.

As for the OMP... I always premixed.

 

The OMP will work if you get a GSL-SE front cover. The GSL-SE cover is different from the 12A front cover.

You can use the oem 12A bracket to mount the 13B. Just cut the holes to accept the longer engine.

 

A series 5 OMP will not fit a GSL-SE front cover. It's an electric type OMP.
A series 4 OMP on the other hand is a 4 port mechanical type OMP and it WILL fit the GSL-SE front cover. You can connect it to the throttle using a bicycle brake cable.

 

If he uses the S5 computer, doesn't the OMP need to be connected so it doesn't go into limp mode?

I know an S4 is an easier swap.

 

Yes that's correct. Very good point. However, I can't remember whether the EOMP needs to be operational or simply connected for the factory ECU. It does have a position sensor in it which feeds back to the ECU. The problem is that it's a different bolt pattern. The series 4, GSL-SE and 12A turbo all use the same style OMP.

Personally, I wouldn't bother with the factory ECU. There are a bunch of other inputs it probably wants too. I would go aftermarket and use that to control everything. You can extract more power out of it that way as well.

 

All of this makes me want to proceed with making brackets to use the FC mounting locations. I'd rather not mess much with the electronics, the factory setup is more than adequate for the FB's light weight chassis.

 

If you're going to go to all this work, you might consider a full front subframe swap. This gets you the big brakes, rack-and-pinion, engine mounts, etc.

 

The FC motor mount locations occupy the same space as the stock FB steering components - it would be difficult to make something work which is why everyone does the SE front cover and oil pan swap - makes a very simple install. If you're going to go through all the work of fabricating up motor mounts etc (which might not even work) you'd be better off doing the whole FC subframe as Kansas says above...

As for the S5's omp - it simply needs to be connected for the ECU to be happy, on one of my swaps I have it hidden up in the dash and so far no issues

 

That's what I am thinking, FC sub frame, rack and pinion, but I want to stay 4 lug if possible. Do you know if the 4 lug FC will clear the factory 13" alloys?

 

I haven't tried so I can't say for sure, but it might clear that rotor - however the FC 4 lug pattern (4x114.3mm) is not the same as the 12a FB lug pattern (4x110mm) so you would need adapters...

Another concern - the FC's track width is already wider than that of an FB, and the FB wheels have slightly less of an offset than an FC wheel, so even if the wheel would bolt right onto the FC hub, it will stick out noticeably more than stock. Add the needed adapter to change lug pattern in there and you're gonna be sticking way out...

I get the desire to keep the stock wheels and keep the car looking stock, but at that point it wouldn't really look right anymore, at least in my opinion Just my 2 cents...

 

if you go with FC 4-lug hubs, you can use the gls-se wheels as they are the same 4x114.3 bolt pattern which would give you a relative stock appearance, with the only issue being the factory wheel offset compared to FC offsets.

 

I am using the FC 4 lug hubs on my FC subframe conversion. I already have custom 3 piece 17 inch 114.3x4 wheels with perfect fitment.

To ensure offset and track remains the same, I am using FD brake rotors with a suitable spacer.

If you have the 13" 4x110mm wheels, this won't help you, but the offset and track is the least of your problems. You're going to need custom brakes anyway as even the smaller 4 lug FC brakes aren't going to fit under a 13" rim and the smaller FB brakes aren't going to fit on a FC strut with 4 lug hubs. May as well use turbo brakes with the 4 spot calipers (which will bolt on) and fit some 15" inch wheels. The dial tone wheels off a Mazda Cosmo/929 are 15" with 4x114.3mm bolt pattern and look fantastic on an FB when polished -!:



That way you can have Mazda OEM wheels with FC turbo brakes