We are using RX-8 rotors in one of our SCCA E/Production "street port" 86-91 13B non-turbo engines.

We do no mods to the rotors (except installing the racing rotor bearing). We are using RX-8 racing ceramic apex seals (the OEM RX-8 steel seals warped too much having to cross the exhaust port). (There IS enough metal to cut the apex seal groove for either 86-91 2mm seals or earlier 3mm seals -- we are looking into making that service available, but are not ready yet) The rotors are run "backwards" (front in rear, rear in front) so the angle cut on the side of the rotor gives more intake opening timing (RX-8 uses the cuts for the side exhaust ports). Do not use the "oil scraper ring" outside the second oil control ring. DO NOT use RX-8 corner seals -- they DESTROY 86-91 side housings !!!! (use 86-91 corner seals, TRUST ME).

They ARE lighter than 89-91 non-turbo rotors, have higher compression, and are less expensive.

With all of the above said: We have YET to attain even the SAME horsepower on the dyno as we are getting from our race engine(s) using the 89-91 non-turbo rotors !!!

Potentials: With the RX-8 rotor having the side seal further outboard, we were able to increase the (ported) intake opening timing versus the earlier rotors -- it may be too much ??? (does not seem likely)

Running the rotors with the angle cut for intake opening may also be in the above category.

We always set pre-92 side seal clearance at about .0015 (1 1/2 thou). The SMALLEST clearance we could get, using the LONGEST of the available "pre-sized" RX-8 side seals was about .010 (10 thou), with the worst on this set of rotors of about .016 (16 thou). This gives a much lower "sealing" than we like.

Other than the above, at this time we are not at all sure why the power is less than when using the earlier rotors.

No, we have not done the REAL test -- run the SAME engine on the dyno, and only swap the rotors (backwards, then normal). That equals three builds, and three full dyno on-and-offs + dyno sessions.

Dave Lemon,
Owner of Mazdatrix,
The dyno operator and driver of the E/P car

I have an "update" since that original response ----- We took the "RX8 Rotor" engine apart (having MASSIVELY over-revved it when the trans broke in practice -- probably hit 14-15k at least, AND did it 3 times. Broke a few tension bolts, cracked gears, spun a bearing, etc.but still ran the whole Thunderhill Double National weekend!!). We ran it on the Dyno (dyno had been up-graded to full computerized) before taking it apart (did not know how much damage had been done). Rebuilt it, AND changed the porting some, AND used 89-91 rotors, ---- AND got about the "same" low power !!! REALLY puts a question mark back on/about the RX8 rotors. So --- WE still have not seen any MORE power from them, but WE are seeing (WITH the porting we had been using) "about" the same power ??????

Obviously, more testing needs to be done.

Dave Lemon ---

TurboIIGuy - 13b rotors are 13b rotors for the most part. Yes the RX8 rotors can be used with a few short upgrades.

badfish229 - Why would you think that? The 8 is only 10:1 compression barely 1 point over the 89 to 91 NA motors.

Yes if you keep going up then higher octane is needed but if this was the case here do you think RX-8s need to run on C1 race gas or something? It has been engineered from Mazdaa that 10:1 is the highest compression the current rotary design can see before a loss of HP is starting to be obtained due to the elongated combustion chamber.