initial D is REAL!

Hey guys. Im just checking to see if anyone has done the rx8 rotors and/or E shaft in the 6 port engines. Im really wondering how the lighter internals with higher comp is.

lax-rotor

iTrader: (1)

There's really no benefit to doing this on a street car unless you upgrade the cluster as well and other components along the way. A majority of the extra reported HP comes from the Renisis' VDI. Going from an S5 to an 8 you don't get 40+ hp at the flywheel from .3 increase of the compression ratio.

Beyond that the internals are lighter so the redline increases upwards of 9k. However I can't remember the max HP in the RPM range, so minimal increase would be seen on a basically stock beyond the rotors and E-Shaft. You'd have to run a stand alone or some other form of engine management to get the full benefit (avoiding fuel cut, increase rpm range, etc).

arghx

iTrader: (3)

I think Racing Beat did a comparison and found little hp gain from the Rx-8 rotors alone. I want to say the stationary gears are stronger though.

lax-rotor

iTrader: (1)

You will get a gain, however comparing an S5 to an RX8 you won't get that much besides response and increase of RPM limit comparably speaking.

The S5 Compression ratio is 9.7:1 (assuming N/A, can't be comparing apples to oranges now)
The RX8 Compression ratio is 10:1
If you're going to do this to an S4 it might be worth while... but I doubt it: 9.4:1

You will net a small amount of HP from switching to the higher compression rotors but you will not net the extra 40HP from just switching rotors, I'd be weary of any reported gains that would significantly warrant the tear down and rebuild just for the Rotors and E-Shaft (that is not to say there's nothing to be gained from doing it if you're already rebuilding the engine).

Of consequence look at the the HP increase from the S4 to the S5 N/A's. You'll notice that the increase is anywhere from 10-20HP (I can't recall the numbers right from my head), but a majority of that increase comes from the VDI.

The stationary gears are harder, and many places offer swapping out the current rotors stationary gears and replacing them with the RX8's. That seems much more common. (I can't recall either if swapping the Stationary gears if you need to swap the E-Shaft as well... I think you can run an FD E-Shaft and be okay.)

Shainiac

iTrader: (7)

The stat gears are not only stronger, but they have multi-window bearings for better lubrication of the e-shaft. IIRC, they also have more clearance for higher RPM opperation.

Realistically, Buying the entire rotating assembly for a street car would be a bit of a waste - especially on a stock port motor. On a heavily ported motor where power would peak much higher, it would be a descent mod for reliability and safety. Also, remember that if you get the rotors, you also need the front and auto counterweights to have everything balanced.

Black91n/a

I read a report that someone actually got lower compression test numbers from RX-8 rotors compared to S5 NA rotors, so you may in fact loose power.

lax-rotor

iTrader: (1)

I think we're going to need links to all these references for future reference.