Rx8's are everywhere, for $1-2k usually low mileage and nice. I want to put a MX3 engine in one. K8ZE
It won't be fast any other reason not to? Oh right any other modern 4cy has more power.
Ok, what readily available and cheap 4cy is best for this swap. Saab Ecotec?
I'm just here to enable.
If you're having fun with it, I say the more unusual the engine choice, the better. 
I think the plentiful and cheap 2.5L Ford/ Mazda is very compelling. Leverage NC miata chassis commonality. Unfortunately not bolt in, I think that requires modifying the firewall, and maybe affects things like wipers and hvac.
The presence of the Busso V6 and its amazing sound is my main counter-argument.
In reply to akylekoz :
You're in Grand Rapids right?
This is just a bit North of you.
For $400 you'd get everything you need for the swap. Engine, transmission, clutch, and computers. I can't convince the rest of the team to jam it into the Volvo, so I'm sharing it with you:
Found this last night
In reply to Indy - Guy :
Geez, I'd love one of those for my NB track car. That's a great price.
In reply to brandonsmash :
Right ! ? !
I've T-5 transmissions alone sell for that much (well, at least advertised for that much)
In reply to Colin Wood :
Inline 5 turbo volvo :)
For me the reason not would be that don't those have quite a bit less power?
I don't see the point of doing a custom swap into a car for it to be LESS powerful. The whole reason I did an OBD-I S52 swap into my '88 325is is because with the other mods I added about 100whp over the M20. I wouldn't have swapped in an ETA motor for example.
Did somebody say Rx8 swap?
The big issue is gearing. If you use the stock rx8 gearbox and rear-end, you will be turning like 5k rpm at 75 mph. That might be a slight exaggeration, but not by much.
So, you either need to use a gearbox that is geared pretty tall, find an engine that is happy spinning 9k, or change the rear diff ratio. The only ratios that can be put in the stock rx8 diff case are 4.44 (stock for S1), 4.77 (stock for S2), 4.1 (stock for FD manual rx7s), or 3.9 (stock for FD autos).
I chose to use the 4th gen camaro t5 as it uses a torque arm stock in the f body. I adapted the mazda power plant frame to attach to the T5. It also has like a .63 overdrive for 5th gear.
With the 60 degree bell housing pattern, you are stuck with the following engines:
1)LS4
2) Northstar
3) 60 degree v6 (I chose the 3900 lz9)
4) the 3300 or 3800 90 degree v6
5) shortstar
6) some old jeep engines
7) some of the gm 4 cylinders
8) some izusu engine (3.6 v6 iirc).
That is unless you want to figure out a trans to engine adapter.
Let me know when you figure out the drivetrain and I can help with the Mazda electronics side of things.
Edit to add... the ecotec engines share the dowel pin locations of the 60 degree pattern, but the bolt holes are all a bit off. This could probably be remedied as some of them are just slightly off.
Can you use a VW/Audi 1.8t? The b5 and b6 platforms used a longitudinal engine configuration, and if you get an AWD transmission, you can convert it to RWD (or you can have a Quattro RX8).
confuZion3 said:Can you use a VW/Audi 1.8t? The b5 and b6 platforms used a longitudinal engine configuration, and if you get an AWD transmission, you can convert it to RWD (or you can have a Quattro RX8).
With that trans and the stock rear-end it would turn just under 4k rpm at 80mph. Gear limited to a top speed of 125mph (assuming a 6k redline) 7k redline gets you a respectable 145mph gear limited top speed.
Edit for clarification: Assuming an O2 trans with .83 overdrive.
The NC Miata rear (and front) subframes bolt into the RX8, which should generally mean differential (and transmission) too. And if you want taller gearing yet, there is a direct fit 3.73 R&P. So that should resolve the gearing issue. Then it is 'just' the matter of an engine swap solution (MZR, turbo MZR, or K24/V6 'kit') in an RX8 engine bay.
In my head it goes something like this... Since you need the NC stuff anyways, might as well buy a whole nice running NC to go with the nice running RX8. In the process you can end up with the novelty of an RX8 powered Miata that could help fund the piston powered RX8. It's that simple, right? 
Driven5 said:The NC Miata rear (and front) subframes bolt into the RX8, which should mean transmission and differential too. And if you want taller gearing yet, there is a direct fit 3.73 R&P. So that should resolve the gearing issue. Then it is 'just' the matter of an NC engine swap solution (MZR, turbo MZR, or K24/V6 'kit') in an RX8 engine bay.
In my head it goes something like this... Since you need the NC stuff anyways, might as well buy a whole nice running NC to go with the nice running RX8. In the process you can end up with the novelty of an RX8 powered Miata that could help fund the piston powered RX8. It's that simple, right?
The NC does have a smaller diff. The axles are different and I believe the hubs and uprights. It does all bolt into the rx8 though. (Actually, not entirely sure the floorpans are the same in that area. Might need to do some percussive maintenance near the nose of the diff.)
I'm not aware of any issues that might crop up by mixing and matching.
Not sure which shocks to use as they are different.
Just read through a bunch of info and the NC diff looks like it is good to about 300hp or so... if I had known that, I might have gone a different direction with my swap! However, it would have made it more expensive. Still probably could have done it within challenge budget after selling the stock diff.
sevenracer said:I think the plentiful and cheap 2.5L Ford/ Mazda is very compelling. Leverage NC miata chassis commonality. Unfortunately not bolt in, I think that requires modifying the firewall, and maybe affects things like wipers and hvac.
This is what I'd do, but everything I read says the firewall in the RX-8 is closer to the front wheel center line than in the NC. Otherwise, it would be a nice 250HP GT with the swap. An LS swap is nothing new, and the 2.5 ford can't be much longer, so I'm not sure what's best.
The part of the firewall that needs removed is just the wiper cowling. I do not believe it requires interference with the wipers or HVAC.
Besides, if you are gonna swap and fabricate some mounts, just move the engine slightly forward if needed.
In reply to Indy - Guy :
That sure sounds like the answer to the question. What are the objections? That drivetrain probably makes more power than the 302 V8.
Indy - Guy said:In reply to akylekoz :
You're in Grand Rapids right?
This is just a bit North of you.
For $400 you'd get everything you need for the swap. Engine, transmission, clutch, and computers. I can't convince the rest of the team to jam it into the Volvo, so I'm sharing it with you:
Found this last night
I have no idea why that isn't sitting beside the Volvo yet. 205 hp stock. Plus they make headers, cams, superchargers, etc for that thing.
wvumtnbkr said:Did somebody say Rx8 swap?
The big issue is gearing. If you use the stock rx8 gearbox and rear-end, you will be turning like 5k rpm at 75 mph. That might be a slight exaggeration, but not by much.
So, you either need to use a gearbox that is geared pretty tall, find an engine that is happy spinning 9k, or change the rear diff ratio. The only ratios that can be put in the stock rx8 diff case are 4.44 (stock for S1), 4.77 (stock for S2), 4.1 (stock for FD manual rx7s), or 3.9 (stock for FD autos).
I chose to use the 4th gen camaro t5 as it uses a torque arm stock in the f body. I adapted the mazda power plant frame to attach to the T5. It also has like a .63 overdrive for 5th gear.
With the 60 degree bell housing pattern, you are stuck with the following engines:
1)LS4
2) Northstar
3) 60 degree v6 (I chose the 3900 lz9)
4) the 3300 or 3800 90 degree v6
5) shortstar
6) some old jeep engines
7) some of the gm 4 cylinders
8) some izusu engine (3.6 v6 iirc).
That is unless you want to figure out a trans to engine adapter.
Let me know when you figure out the drivetrain and I can help with the Mazda electronics side of things.
Edit to add... the ecotec engines share the dowel pin locations of the 60 degree pattern, but the bolt holes are all a bit off. This could probably be remedied as some of them are just slightly off.
Little known fact but the Saab B/H engines bolt onto a T5 from 98-99 Isuzu Rodeo 2wd.
wvumtnbkr said:Indy - Guy said:In reply to akylekoz :
You're in Grand Rapids right?
This is just a bit North of you.
For $400 you'd get everything you need for the swap. Engine, transmission, clutch, and computers. I can't convince the rest of the team to jam it into the Volvo, so I'm sharing it with you:
Found this last night
I have no idea why that isn't sitting beside the Volvo yet. 205 hp stock. Plus they make headers, cams, superchargers, etc for that thing.
well, it is 5 hours north of here.
But yeah, that's a lot of engine swap value sitting in one place. Also, we seem to have a different route to extra horsepower every other day.
Indy - Guy said:wvumtnbkr said:Indy - Guy said:In reply to akylekoz :
You're in Grand Rapids right?
This is just a bit North of you.
For $400 you'd get everything you need for the swap. Engine, transmission, clutch, and computers. I can't convince the rest of the team to jam it into the Volvo, so I'm sharing it with you:
Found this last night
I have no idea why that isn't sitting beside the Volvo yet. 205 hp stock. Plus they make headers, cams, superchargers, etc for that thing.
well, it is 5 hours north of here.
But yeah, that's a lot of engine swap value sitting in one place. Also, we seem to have a different route to extra horsepower every other day.
I assume that you are on the way back with it at this point. It was over 5 hours ago when you posted.
Lolz.
Golly, that 3.8 combo is 2.5 hours north of me and the right price. I would buy that just for fun and old jeep shenanigans.
I'm rapidly closing in on the time of life that I will have a bit more time for a project car. Not retired just grown up kids.
An RX8 project just seems right, back seat for grand kids, cheap to buy. An MZR 2.5 is probably the best choice and just let it scream or regear it. I'm a machinist with a water jet and all the steel I could ever want so an adapter is not out of the question.
Now what about a 2zz for the rpm factor? Almost the same HP and gearing should line right up.
Now shopping for Corolla XRS, Vibe GT, Celica GTS, Matrix.
Today I can get a running leaking Vibe GT and a nice RX8 for $2500 all in for both. This is the plan...someday.
I thought the big thing with RX8s was swapping in an LS V8. I mean, if you're going through all the trouble of a swap it may as well be for ridiculous horsepower. 
Isn't the 2ZZ like ~30hp down from factory and less torque than the Renesis?
Not saying it's a bad idea though!
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