any methods to drop the compression on them

 

Why bother when you have the 8.5 c:r and 9:0 c:r rotors?

 

because its a lighter rotor

 

I believe there isn't much left to machine on a RENESIS rotor. It is true you can retrofit one into older 13B's, but I think there is a side seal issue.

 

yeaa, right now they are still loosing power with the renisis rotors.....I'll find the link

 

http://www.racingrotary.com/rx8rotors.htm

mazdatrix info, I trust mazdatrix

 

what year 13b has the lightest rotors and wats the compression on them?

 

You didn’t read the bottom update.

Update August 2 2004 -

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 ---

 

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 ---

Hmmm....

Different porting and "about the same HP", doesn't make any sense to me, maybe they were somewaht vague on the explanaiton.

 

basically its still shady....and not really worth it

 

very strange

 

interesting.....

 

Has anyone approached mazda about supplying over-length side seals?

 

And about the weight of the rotors, rx8 rotors are still heavier than race lightend S5 rotors.

 

I asked about using longer side seals to a member of the RX-8 Forum. Here's what he had to say:

It's strange how there is increased clearance for the side seals. This can quickly turn into a problem when porting the motor.

 

I have used RX-8 rotors for a PP N/A engine. It made 284 hp@8600 rpm compared to a similar 9:0 cr PP engine i built last year (it made 276 hp@8200) The real gain as i see it is in the midrange where the "RX-8 engine" picked up 10-15 hp. The hp on these engines is flywheel hp and the "RX-8" engine has since dyno'd in June been to a reputable rolling road where it made 303 hp converted to flywheel hp. All i can say is that RX-8 rotors works great for PP engines and the car an RX-7-83 rally car won it's first victory on a 1km long hill climb event 1.5s quicker than second car which was a Mitsubishi EVO 6 turbo rally car! On third place, 3 seconds behind the RX-7
was a N/A Escort with a 2.3l Pinto engine. I said go rotary!

 

I'm waiting on a certain supplier for reply if or not the RX-8 side selas can be dupplicated. Should have a reply in a week or so.

 

I hope that's an error! You meant 9.7:1 compression right?

 

No i really did use 9:0 cr rotors becausse cuctomer didn't have the money for new 9.7 cr rotors. How much increase in hp do you think is available with new side seals? Hopefully this winter i can build a 10:0 cr dragracr PP engine with big inlet holes, that should be intersting hp wise!

 

That would explain the power increase you experienced.
As for power increase with the new side seals there should be some significant difference. Even with the longest side seals available from Mazda presently for the rx-8 the clearance is way beyond the maximum amount normaly used on regular motors to operate efficently.

 

I hope very much that longer side seals can be available in the near future! Today i have the fortune to build another 13B PP rallycross engine for a customer in Sweden. Goal is to achieve at least 290 hp with a torque of 190 ft/lb at flywheel. I shall use a new Gene Berg carb but don't exactly know what size i shall go for? 52-56 mm i think should be good for hpand torque. I have seen vacuum drops for about 0.2 bar at 9000 rpm with aWeber 51 IDA. Any inputs carb gurus?

 

was at atkins the other day, a guy came in asking questions about the rx8... wanted to know how much lighter the rotors were... on a scale, the rx8 rotor atkins has weighs the exact same as a 3rd gen rotor...