----- Original Message -----
Sent: Wednesday, April 13, 2005 2:38
AM
Subject: [FlyRotary] Re: Rx-8 Rotors in
Rx-7 Block
It would seem to me that they are saying they run
the rotors backwards - that would put the recess in the rotor face
backwards.
The deeper side is to the side of rotation I'm
sure that would cause some power loss - then again I'm not the
expert!
The ceramic apex seals are the seals of choice, I
didn't know they were that expensive!
George (down under)
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