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Building a solid rotary

General Engine Building Discussion

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Whats up everyone, this might be a long shot of a question, not sure how well versed in rotarys everyone here is.

Im building up a second gen rx8 and plan to turbo it. the goals for the car are 400-500 hp and reliable enough to hit some track days. pump gas and meth injection for fuel with an air-air intercooler

What im trying to figure out is the best combination of plates and housings is to make this possible. currently ive got the good running s2 renesis thats in the car. my plan was to get a rew and run the rx8 front cover so i can hopefully retain the factory ecu and electronics.

after doing a little research i thought it would be cool to reuse the renesis eccentric shaft and rotors since they are lighter and have a little more compression

so what im curious about is should i use rew housings and plates? does it matter what model rotary motor the parts are from if its going to be ported anyway?

the other thing ive looked at is building a semi pp renesis with side and peripherial exhaust ports but i feel like it could have a negative effect on spoolup due to the increased volume of the exhaust manifold. this could be the cheaper/easier way to go since i could either have my housings milled or just run a different set of rotor housings and keep the rest of the motor

thanks for any direction

Mark

Hi Mark, sounds like a fun project. Unfortunately while I've got a limited amount of knowledge around the older 13B-REW engines I'm not familiar at all with the Renesis engine. In particular I've got no idea on parts interchangeability between the REW and Renesis engines. The higher compression of the Renesis rotors might not be the best for a turbo combination too. While I know there are a few turbo kits floating around for the RX8 for the stock engine, this likely isn't the ideal scenario, particularly given the rotaries fragile nature when detonation occurs.

I'd also say that your concerns with a semi PP exhaust port are probably warranted and I think if you wanted to go that way you'd probably be best to eliminate the side ports altogether and just run a conventional peripheral exhaust port. At this point you're almost best to just fit a 13B-REW engine and be done with it though.

The side exhaust ports on a renesis are way less than ideal for turbocharging as they expose the side seals to far more/higher EGTs. Unless I were forced to I'd basically never turbo one. Were I you, I would be running REW plates and rotor housings (though s5 is just as good once you're going full aftermarket really, I don't really subscribe to the idea that the chrome plating is all that much better on REW housings), S4 (1987-88) turbo rotors that you can have lightened and balanced, and a GSL-SE eccentric shaft.

That would be the most bulletproof turbocharged mix, in my opinion. Large ports from plates you can get factory new (RE plates are arguably better if you're using its manifold) with minimal core shift, lowest compression rotors that end up being as light as REWs if done properly, and while the GSL-SE e shaft is heavy they also don't flex. Shoot me a DM if you're curious about any other rotary stuff, or just post here, I'm happy to help.

The REW or RE (COSMO) plates have more meat and are less likely to crack at the dowels. S4T rotors are strongest but any from there forward can hold big boost if they don't suffer pre-ignition.

There are mixed opinions on improving surface area in coolant jacket around the plug bosses (at high power the plug bosses swell and can lift apex seals over the plug area), even relieving around the leading plug hole slightly on the chrome side, likewise adding additional dowels or aftermarket bolts/studs, I bought the turblown 10mm studs myself.

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