I blew my coolant seals like a bozo, and I'll be rebuilding pretty soon. I know a guy who got an RX8 crazy cheap, won't run, too low on compression. He's thinking about putting some sort of piston engine in it, and if he does he told me I could have the renesis.
Will the eshaft, or anything else, save for the high comp rotors (premium gas not always available here, so I'd like to stick to regular) from that Renesis let my s4 NA rev higher, or make more power? I'd certainly like to have a 9000rpm streetported s4... but I might be dreaming.

I heard the eshaft would need balancing to work at all with my s4 rotors and 'any good machine shop can do it' - how good is good enough? I know a bunch of guys at my university who do a lot of machining and would happily help me out for cheap or free.

In case you haven't already figured it out, I don't have a huge budget. Enough for a streetported, rebuilt S4, but not way too much more than that. If people have tried this before and it turns out really expensive please tell me. Though I haven't heard anything like that from the research I did.
I would much rather look dumb on a forum and later have a running streetported s4, than look dumb when I spend a bunch of money on a s4-renesis hybrid just for it not to work out.

 

My wifes rx8 runs great on 87 octane, thats all she runs in it.

 

You want the S5 N/A stuff. The Renesis engine is very different due to the exhaust ports on side housings, not the rotor housings. The rotors are different and use different seals. Also, the intake manifold and induction system runs of electronic throttle.

 

I was not aware. Many RX8 guys I know tell me that even if you don't drive it hard, you'll get knock and break an apex on 87. Good to know that's not the case.

S5 stuff is crazy expensive around here-and that's when you can find it. Somehow it costs almost as much as REW parts. I know the

I was thinking I might be able to use the RX-8 eshaft, with the irons, rotors, side housings, etc etc. all from the S4 engine, in hopes that I could safely run it till 9000 RPM. Whether the s4 intake, exhaust, etc etc can flow enough air to make power at 9k, that's a whole other question, but it would be way easier to get a better intake and headers than to swap a 15 year old engine into a 35 year old car, lol.

 

I did some research on this, plus I have some info I got when I emailed Pineapple Racing on the topic.

You can run the Rx-8 e-shaft in an S4 engine as is. Apparently balancing the rotating assembly is optional, but I'd definitely do it if you want 9000rpm. You can also run the front and rear stationary gears from the Rx-8, they are hardened and come with multi-window bearings. The Rx8 e-shaft is .6 lbs lighter than S4.

The Renesis rotors are lighter which helps with the high redline, so if you're not concerned about cost then having the S4 rotors lightened and balanced might be a good idea. Otherwise I'd imagine periodic high rpm use should be okay.

There is one mod required for the stat gears. The rear gear doesn't have the o-ring groove required to seal in the S4 rear iron. You can either have this groove machined in by a shop, or apparently just use a skim of RTV.

 

WondrousBread provided 99% of what i would say.

there really is no major advantage to scavenging your friend's dead Renesis in your case. the stationary gears are worth getting, but they are not going to add anything except insurance when you achieve what you want (and it sounds like you want 9000 RPM). more often than not, the bearings are affected when these MSPs go, so even if you got them it's likely you would have to spring for new bearings (and they cost more). if you have to get bearings for your engine now, then it's no real big deal, but if your bearings are fine, then it's an extra cost. i mean, it's worth checking out because you may get lucky, but i wouldn't hold my breath.

the shaft can be used as is, but it adds nothing by itself either. the rotors are lighter, but they also have the shorter apex seals. they apparently don't like peripheral exhaust ports much, so you would probably be advised to modify the rotors for use with the taller seals. again, extra cost.

the Renesis was designed for the things it can do, so it's not a matter of magic parts. the lighter parts help, but it's more the accumulation of everything - the ports (the old 6-port [even when streetported] cannot compare to the MSP stock), the lighter parts, the intake design, the zero overlap, the ECU, etc.

just build the best version of your engine that you can afford. do some oil mods and make it as reliable as you can. maybe do a flywheel somewhere down the line.

 

Depending on how much your friends are willing to machine parts for you, the rx8 rotors can be made to use rx7 seals and lightened even more.

 

Everyone else has pretty much covered your questions about the Renesis parts. A few things I would add. If you get in your engine and your rotor housings aren't usable then buy TII rotor housings. If yours are usable or you get a good deal on usable N/A ones then replace the stock exhaust sleeves that have the diffusers in them with these EXHAUST SLEEVE, TITANIUM 13B | Mazdatrix TII housings don't have diffusers. Can't really streetport the exhaust with the diffusers in there. I think to run at 9000rpm continuously there is some clearancing on the sides of the rotors that needs to be done. For the occasional blast to 9000 they say you should be fine. You are going to have to have something other than the stock ECM to ever get to 9000rpm. Rtek used to be an option for making the stock ECU programable but they aren't around anymore so beyond a used one of them a standalone ECU is your only option.