Appended below is an e mail from the owner of
MazdaTrix about using the Rx-8 rotor in an RX-7 block. Interesting
reading, now if only the ceramic seals were not $3600 for a set for two rotors
I'd be ready {:>). Makes for interesting reading.
Here is an e-mail that Dave Lemon from Mazdatrix sent an RX-7 forum
member on the subject. Just thought you guys would find it
interesting:
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