Gah I can't believe I forgot about compression ratio in the other thread!

These guys are right. For a turbo car you want low comp rotors, usually. I say usually because if you hit up the FC or Canadian sections and look up threads by Aaron Cake, you'll see a crazy build that involves a high-compression N/A FC engine being used for a high-comp turbo setup.

For N/A, you want higher compression rotors.

So that begs the question : What is the best N/A 13b rotating assembly aside from the Rx8.

The Rx8 takes the cake because of its 10:1 comp rotors and ultra-light e-shaft, but assuming that RENESIS internals aren't the easiest or cheapest thing in the world to come by, what would be next?

I think Cosmo 13bs were turbo'd, FDs were, any TIIs were.. so it'd be S5 N/A rotating assembly, then just finding some 4-port housings and irons.

So S5 N/A rotating assembly with S5 TII housings would make a good N/A combination, barring the availability of RENESIS internals?

This is all theory in this thread, I don't think anybody but Jeff actually has an engine build on the books in the near future, just discussion on different franken-engines.

Jon

 

My engine build is definitely in the works as long as i can find a decent job, lol

 

its not a theory on the renesis internals. My buddy got one and Im planning to go that route also

 

my ? is why do you want high compression rotors with a turbo? They would call that a hard tune. High compression motors boosted motors just plain suck to tune. Your gunna have to run rich to make sure theirs no predet, but then your idle you spit out alota extra stuff u dont want out the exhaust. Lower comp ratios and boosted is the best for the tuning. And to make a great street car it will have to be tuned very well. Im not a big fan of Sport Compact Car magazine but their second issue this year of the ultimate street car championship talks about tuning and i suggest you pick it up before you start building. Could be helpful.

 

If you're referring to me, Im going N/A as usual

 

TII parts aren't easily available to everyone. Many have said one can't turbo an NA engine, have it hold together and make big numbers, Aaron has been proving them wrong, big time. It can be done and tuning is even more critical than with low comp rotors. What most fail to realise at first glance is boost psi can be run lower to make the same hp that low comp rotors do. Same stress on the engine, less on the turbo.

Fwiw, high hp low comp engines generally run AFRs in the 11.5-12.0 range at full boost to prevent detonation.

 

^^ i love the high comp rotors. makes for a very snappy motor. tuning isnt really an issue since im running standalone and anyone wanting more than 20hp over a stock s5 t2 motor should serioulsy concider it. stock injectors will give you lean spots and upgraded injectors is wasted fuel and staging issues. again detonation can be avoided by retarding the timing and a decent hi grade fuel.

also.. stock ports are meh on the na motor. so if you want to build a 4 or 6 port na motor then at least get the t2 intermediate iron. the ports are somewhere 20% bigger than the na ones and no porting is needed.