RX7Racer46

K, so the S4 has 9.4:1 Rotors on the NA and 8.5:1 Rotors on the Turbo II. I was wondering if anyone has ran the 9.4:1 rotors on their turboed engines and does this help or hurt the overall power of the vehicle under high boost, like 15-25lbs.

And I believe the S5 has 9.7:1 Rotors on the NA and 9.0:1 Rotors on the Turbo II. Why the increase?

Thanks,

Steve

Spectator

iTrader: (1)

Theres a huge difference between 15 and 25 PSI. Which one are you looking for?

RX7Racer46

True, Ill be running 20PSI on my next motor.

Mankdrake 2661

iTrader: (8)

Higher compression = more HP Boosted or not.

Now that being said, the higher compression with a turbo will most likely not last as long.

RotaryResurrection

iTrader: (8)

I would not run hicomp rotors in a turbo engine that will see more than about 10-12psi MAX.

Stock for stock, the hicomp rotors will always make more power, and at stock boost levels they are not a liability. They help slightly with low end, mpg, and spool. SLIGHTLY, as in the average person would not be able to test drive the car and know that it had high comp rotors.

However, at higher boost levels they become more of a liability and they limit your power because you cannot continue to safely raise boost.

It's more than most people can do to keep a low compression turbo rotary in one piece at low to meduim boost, much less making it more challenging by raising CR and boost.

initial D is REAL!

A turbo will lag the same amount either if you boost 7psi or 20psi. Higher compression helps spoolup a little, but you wont be able to boost as much. I was jsut watching a show interviewing the owner of Bank's Engineering,a nd he said every pound of pressure is a 7% increase of power. I dont know how true that is, but wouild u rather have a 9.5:1 boosting 7lbs or a 8.5:1 compression boosting 12-15lbs. Not that those are real boost #'s.

I gues you have a running engine right now and just want tobolt a turbo setup to it? If your building it, low compression is the way to go

RX7Racer46

Right now I have a Street Ported 13BT with a T04 turbo. (Check out my VB Garage) She runs great. No problems at all. Running stock boost. Soon to be building a bridge ported 13bt and dropping that in with a whole buncha goodies (too many to list). Doin engine swap because I have a hair line crack on my rear rotor housing and slightly leaking oil.

RotaryResurrection

iTrader: (8)

Sounds like you cracked the rear iron's dowel casting due to some hard pings. I have never seen a cracked rotor housing leak oil.

http://www.rotaryresurrection.com/2n...ron_break.html

So if you couldn't keep this engine from dying while "Running stock boost" then why make life more challenging by raising CR AND boost at the same time?

TitosToy

it's kinda funny how we call the 9.4:1 high-comp rotors and iirc, isnt the s6 rotors 9.3:1? and those guys boost them up as 25psi (maybe more). does that .1 make a difference?

RotaryResurrection

iTrader: (8)

<sigh>

http://www.rotaryresurrection.com/2n...nter_info.html

TitosToy

whoops...my bad - you can delete my post if you want

RotaryResurrection

iTrader: (8)

Also, while 0.4 or 0.7:1 CR increases do not sound like a big deal, remember that just as in displacement, boost, fuel and hp calculations, there is a "rotary conversion factor" involved. By the same token that 1.3L of rotary displacement makes the power of a piston engine twice it's size, and small amounts of boost produce more power than they generally would in a piston engine, so too does compression ratio become amplified in importance. This is why tuners and the aftermarket are having difficulty making power with the renesis, due to it's (for a rotary) high compression 10:1 rotors.

TitosToy

good point.

RX7Racer46

I actually slid the car into a curb, bent my passenger rear lateral link and, apparently my motor mount moved a little cracking my rotor housing. Happened second day I owned the car. Had it for little over a year now. Still runs great, but oil mess is annoying. Had nothing too do with over boosting.

RotaryResurrection

iTrader: (8)

The only way I can see this happening is if the motor mount/subframe crushed in a great distance and actually broke one of the "legs" on the bottom of the rotorhousing. OIl does not circulate anywhere inside the rotorhousings except at the top drivers corner where it says "mazda" and of course underneath at the oilpan.