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.

The "response" I gave you was a copy of one I did a few months ago (which he posted on a "few forums").

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 ---

Originally posted by xero
I e-mailed Mazdatrix and he sent me a couple responses he made a couple months back, he said someone had posted them on a couple sites, but I couldn't find them searching, so this [may] be a repeat.





Not having ever worked on a rotary, I couldn't correctly speculate, but from what I can tell, they're atleast the same as S5 rotors in a performance sense, but they are significantly cheaper, except upgraded seals are a must

Originally posted by Lasse wankel
I am using the RX-8 rotors in a PP motor i built for rally. It peaked about 8 hp more and gain 10-15 more hp in the midrange. Milled the apex groove to fit 2 mm Hurley race apex and also side clearnced the rotor land though the step was at some points to small. I also found when i balanced the rotors that one side of the rotors was 10gram to heavy so we "zeroed" the rotors (FC-FD rotors is normally only 1-2 grams off "zero" Also intersting to see was that the rotors had no balancing holes on the rotorland compared to all other rotors i have seen. Also measured the Rotorbearing clearence and found them to be at 0.07-0.08 mm just as the race bearings, but the RX-8 rotors had no deep groove so i made that mod to them.