RX-8 engine swap to MS3 engine-- Idea for a project

jeremy1210

Member
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No mazda right now
I tried searching (not really good at it), but I was wondering if anyone has ever thought
about doing and engine swap for the RX-8. Like changing it from the rotary that's in it to a MS3 engine. I'm not sure if its feasible, but the quick benefits I see are:
-Better reliability
-None of the flooded engine issues
-better mpg (not a big deal typically, but $4-5 does make you think)

Since it's a Mazda to Mazda, I don't for-see there being too many difficulties, but again, I've never done this or read about it. I know it will cost some money, that is a given, but it would be a project after all.

-need new motor mounts
-tranny and axels
-have to get the wire harness meshed

So my question is: Has this been discussed? If not, how does one go about researching the feasibility to do this swap?

Thanks
 
I know nothing of engine swaps but I'm sure it would be a beast of a project. As much as I love the rotary, I think a DISI powered RX-8 would rock!
 
it can be done, but here are a couple of recommendations that i have;
1. use the FS motor instead. yes, the DISI 2.3 turbo motor is awesome, but you will have engine management issues if you go with anything other than the stock harness and ecu. there are piggy-backs, but those are nothing compared to stand-alones. the FS motor would also be cheaper to build.
2. get some skills in fabrication, you will need it for the motor mounts. the easiest way to do them is going to be solid urethane mounts for the rx8 and brackets going from there to the motor.
3. use a miata trans from any miata that has a BP. they are stronger than the rx8 transmissions and they have a better aftermarket following. there are actually some third generation guys swapping for miata transmissions.


unfortunately, there isn't a lot of research material for motor swaps like this. this is kind of a "who ate the first lobster" situation. it can be done, but you have to consider every step in great depth. my final recommendation is probably completely beside your point here; do this with a second generation rx7. cheaper build, but it wouldn't be quite the same i know.
 
This would be a beast of a project, and the outcome would be great. However the reason it hasn't been done is once you are looking at a full engine swap there are a lot of better engines out there to start with. Most people who can do this would prefer the added potential of an LSX or some other V8 with lots of potential power. This would be neat since it would remain a Mazda through and through, but for most people the novelty will not justify the cost. Quick story: Autobarn Mazda was looking to build two custom cars this year (last year they build a Mazdaspeed5 for the One Lap of America). This year they were looking to make a speed2 and a 2011 RX-8 with a lot of boost. One of the vendors locally asked me for advice when they contacted him and I told them to put the speed motor in the RX8 chassis and slap the RX8 motor into the 2. They would have ended up with two unique cars. Autobarn didn't want anything to do with that advice. They are almost done with the speed2 project now, and I believe the RX8 project is dead. I suspected the RX8 project was a dead end since no one has successfully boosted a GenII 8 (correct me if I am wrong). They contacted Turblown who said they could do it, but their track record is not very consistent. They are pushing the limits, which is great, but i don't think many of their builds have a long life after boost (think weeks not even months).
 
I can see your point about using a V8 or something in that ballpark, but I think something unique is cool as well. I don't see this being any less expensive a task than a V8 swap.

I asked this question on another forum and they said that the car would then be a FWD. But if I use the miata tranny then I can have RWD. That is good to know.

Aside from making new mounts, meshing the wiring harness, and making a custom exhaust there shouldn't be any more difficulties right?? lol

I guess it depends on if I can find a wrecked MS3/MS6 and pull the engine with the complete harness. otherwise it would be more challenging. Since they are newer that might be more expensive. You are right that the FS is cheaper and there were more of them. I'm sure I could find one of those pretty easy (just which one??)

Which FS engine? I had the MSP a few years back and it didn't seem like an engine worth dumping money in to. I was thinking the DISI because its pretty good from the get go and has the newer turbo water cool technology vs oil cooled.

As far as the harness, I know a guy who has meshed a few harnesses in his day and can do it for relatively cheap as long as I have both stock harnesses.

Now I am somewhat familiar with FWD engine swaps (6gen celica to 3sgte) but how do the axels work for the RWD?

I just got home from work and this is what I can think of in the work fog... what else should I be checking in to for this?

Thanks
 
This would be a beast of a project, and the outcome would be great. However the reason it hasn't been done is once you are looking at a full engine swap there are a lot of better engines out there to start with. Most people who can do this would prefer the added potential of an LSX or some other V8 with lots of potential power. This would be neat since it would remain a Mazda through and through, but for most people the novelty will not justify the cost. Quick story: Autobarn Mazda was looking to build two custom cars this year (last year they build a Mazdaspeed5 for the One Lap of America). This year they were looking to make a speed2 and a 2011 RX-8 with a lot of boost. One of the vendors locally asked me for advice when they contacted him and I told them to put the speed motor in the RX8 chassis and slap the RX8 motor into the 2. They would have ended up with two unique cars. Autobarn didn't want anything to do with that advice. They are almost done with the speed2 project now, and I believe the RX8 project is dead. I suspected the RX8 project was a dead end since no one has successfully boosted a GenII 8 (correct me if I am wrong). They contacted Turblown who said they could do it, but their track record is not very consistent. They are pushing the limits, which is great, but i don't think many of their builds have a long life after boost (think weeks not even months).

there is one boosted genII in the houston area that i know of. none of the MSP rotaries don't respond nearly as well to turbo as they do to supercharging though.
 
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any well-built FS with a full stand-alone set-up would be a good way to go. with DISI, the engine management options are limited right now. the cost would also be doubled, if not more.

the driveshaft is the only thing that you will have to worry about in this case, not axles. a good trans shop should be able to cut you a driveshaft for under a couple hundred bucks.

the main thing that changes about the water cooling on the ms3/6 turbo is that a water pump keeps flowing on the turbo after you turn the car off. you can do the same with either an electric water pump or a turbo timer.

one problem that you may or may not have is hood clearance. the rotary engine is short and fat. that makes for a wide and deep engine bay that will definitely swap a v8 without a whole lot of lost space, but this is an in-line motor you are talking about here. there may be issues with clearance on the front edge of the valve cover. there also may be radiator clearance issues, but you can buy a radiator to more or less fit the build and just make some brackets for it. there will always be issues with a completely custom swap such as this one, but it is definitely to be expected.
 
Just to be clear: The FS engine is the one our of the MSP, correct?

How would one measure hood clearance?

Since the FS is cheaper and easier to come by(especially with a standalone EMS), is it common knowledge/ been done before, that the miata tranny will bolt up to the FS engine?

I see your point on the TT. I had one in my MSP and it worked fine. I forgot about that.

I appreciate your help Lil Red!
 
there is one boosted genII in the houston area that i know of. none of the MSP rotaries don't respond nearly as well to turbo
Understatement of the year!! It can be done, but you are really throwing the dice. IIRC the one in Huoston was done by Turblown, I didn't know they ever finished that project. Good to know.
as they do to supercharging though.
I think this is mostly due to the superchargers running a lower peak boost, the boost being a lot easier to control and the smoother transition from off to on boost. This option is also a lot more expensive, and will not net as much power per dollar spent. The peak numbers tha tare achievable are lower than with a properly installed and maintained turbo system.
 
I see your point on the TT. I had one in my MSP and it worked fine. I forgot about that.

If you could find a way to retain the twin oil coolers that RX8's come with that would go a long way toward keeping the temps in check, but a TT would be good to have as well.
 
Just to be clear: The FS engine is the one our of the MSP, correct?

How would one measure hood clearance?

Since the FS is cheaper and easier to come by(especially with a standalone EMS), is it common knowledge/ been done before, that the miata tranny will bolt up to the FS engine?

I see your point on the TT. I had one in my MSP and it worked fine. I forgot about that.

I appreciate your help Lil Red!

yes, the FS is the motor in the msp. it also came in all third generation protege's. the FS and BP motors had the same bolt pattern on the transmission side, so it shouldn't be any problem. a couple of issues to address immediately will be trans mounts and engine mounts. there may be issues with shifter location, but I really don't foresee any issues.

for hood clearance, you just need to mock up the fitment. do that before you build a motor.
 
I do have one question that someone brought up to me: is it possible to take the FS since its transverse and make it longitundinal? Or would it just make more sense to get the BP since it was made for RWD

I'm not sure if there would be enough room in the bay to make a transverse engine fit...
 
I do have one question that someone brought up to me: is it possible to take the FS since its transverse and make it longitundinal? Or would it just make more sense to get the BP since it was made for RWD

I'm not sure if there would be enough room in the bay to make a transverse engine fit...

Space would be a problem. The inline engine is much taller than the rotary, so it might cause stock hood clearance issues. Second, you can mount the fs longitudinally. However, there are going to be drawbacks. On my fs, the thermostat housing is on the right side of the engine block. The right side would be the rear if you mounted it longitudinally(since it is where the flywheel is). This would make it where your thermostat would be hard to access, and you would have to have a several foot long radiator hose to reach the back of the engine. I'm sure it could be done, but it would be awkward. This picture might explain it abit better.
40558580.jpg


As you can see the coil packs thermostat and other components are on the right side of the block, and by being put in the rear might drastically complicate your swap.
 
Or you could swap the front subframe for the MX5 subframe and turbo the hell out of a MX5 2.0! Maybe stroke it out to 2.3 then turbo it. I believe the 2.3 and 2.0 MZ motors share the same block but the bore/stroke is what makes it a 2.3 vs 2.0. I know there are people swapping the RX-8 front subframe/motor assemblies into MX-5's, so if the MX-5 motor fits, it should swap into a RX-8.
 
NC miata and RX8 are pretty much the same exact thing, other then engine

the newer RX8s i think 08+ even has the miata trans in it. The diffs are interchangeable as well.
 
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