I was wondering if it would be possible to swap out the rotors (and) maybe the e-shaft to the lower compression turbo rotors/e-shaft in order to turbo an n/a. What is the possibility? because I saw that the compression ratio of a turbo II is ~8.5:1 and an n/a is like 10.x:1.

 

Yes you can swap out the rotors, and eshaft if you want. and if your chancing series ( example S5 NA 9.7 to S4 turbo ) you will need the counterweights also.

) eshaft is the same, but I usually try and keep the eshaft and rotors together if possible, ( and still have good bearings, and everything is within spec )

 

keep the high compression rotors!
well, assuming you are using standalone, it'll result in a much quicker spooling turbo, better low end, and overall better gas mileage.

if tuned well, its the hell of a setup

 

But wont this lead to an earlier failure and at the cost of not being able to run as much boost down the road?

 

or your the same guy that wants to make a custom widebody carbon fiber body kit using gaudy body panels from super cars and high end italian euro trash...

nevermind, i'll research on my own.

Anyone else need some salt?

 

S4 NA rotors are 9.4:1 S5 NA are 9.7:1 & Rx8 rotors are 10.0:1
S4 Turbo rotors are 8.5:1 S5 Turbo rotors are 9.0:1 & FD rotors are 9.0:1


Now with that said, yes you can use lower comp rotors in an NA block, but the question I have is why? Obviously doing this requires a full tear down and rebuild of your NA block so why not just get a rebuilt TII block with the rotors you want? Think about it, if you do this to "turbo an NA" your not really doing that if your using the turbo rotors. Your building a Frankenstein engine by using NA Irons & maybe NA housings with turbo internals. I'm not saying frankenstein engines are a bad thing, hell my next engine is a Frankensteiner(S5 Turbo block with modified S4 TII rotors), and you can port the NA irons to combine the 5-6 ports with the secondary ports to create a Huge port. But unless your going to use the NA irons to make a huge port I don't really see the point in tearing down an NA engine to use turbo rotors when you can do a turbo swap instead.