Rx8 Rotor in FC Information From MazdaTrix
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Rotary Power Information
Joined: Aug 2003
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From: New Hampshire, Greenfield
Rx8 Rotor Information From MazdaTrix
hey all. I have heard lots of rumor and myths about using rx8 rotors in the 86-91 13b non turbo rx7 motor.. so here is an email i got back from mazdatrix a few hours ago.
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
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
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Thread Starter
Rotary Power Information
Joined: Aug 2003
Posts: 528
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From: New Hampshire, Greenfield
Title updated to better reflect post
there was one guy in aussie did put rx-8 rotor in a fc, but the way he did it is to grind down the seal grove and use FC seal
let me go look up what he had done real quick
let me go look up what he had done real quick
Justin
the aussie claim that they are making more power @ 8000 - 10000 rpm
um ... here it is :
http://ausrotary.dntinternet.com/for...3c37856116ab21
http://ausrotary.dntinternet.com/for...=renesis+rotor
um ... here it is :
http://ausrotary.dntinternet.com/for...3c37856116ab21
http://ausrotary.dntinternet.com/for...=renesis+rotor
Originally posted by ViperDude152
The rx8 side housings are cast iron which are stronger but yet sounds heavier.
The rx8 side housings are cast iron which are stronger but yet sounds heavier.
Thread Starter
Rotary Power Information
Joined: Aug 2003
Posts: 528
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From: New Hampshire, Greenfield
I thought they were aluminum which is why i also thought that is the reason for the Rx8 Corner seals destroying the side housings.... hmm. I definatly want to put a pair in my engine. but also want more power..not less then S5 rotors.
Justin
Justin
Joined: Apr 2002
Posts: 4,232
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From: Rotaryland, New Hampshire
There is a thread on nopistons where a buy built a pp motor for a customor and reports a 24hp gain over the 9.7:1 rotors. I belive he used the same setup with the exception of the rotors
he had the rotor groves milled out to accept pre-8 seals, and also didnt use the oil scraper seal
-Jacob
he had the rotor groves milled out to accept pre-8 seals, and also didnt use the oil scraper seal
-Jacob
SUPERnaturally Aspirated
Joined: Dec 2003
Posts: 337
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From: Long Island
there is a really good artical about rx8 hp figures in the december 03 sport compact car.
the ecu goes into dont overheat the cat mode and cuts power.
plus mazda does notoriously overrate engines
the ecu goes into dont overheat the cat mode and cuts power.
plus mazda does notoriously overrate engines
Thread Starter
Rotary Power Information
Joined: Aug 2003
Posts: 528
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From: New Hampshire, Greenfield
I think i saw on SR motor sports.com or ..another site...about the rx8 power. But ya they are more around 170-190hp. Alot of variation between each one. THe 250 I hope is an exageration at the crank because DAMN. thats alot of power missing from the driveline.
Justin
Justin
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