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what a clusterfuck for mazda

sucks



btw, mike. let me know if you can get your hands on any "broken" renesis motors. i doubt it though

sorta like mazda took those crate s4 motors and just trashed em for the insurance money. money money money, they dont care about our engine swapping needs!!!!!

Il RX8 lI

Looks like new engine for me then, bought summer of '03.

j9fd3s

tad bit early to say, but if its running ok, then you probably wont get an engine

j9fd3s

but they are extending the powertrain warranty to 6 years 60,000miles

phinsup

isnt it 5 year 60 to begin with?

Judge Ito

I talked about how the renesis had durability issues, how my Rx8 went from 108psi on every rotor compression chamber to 95psi in a short time after serious racing abuse. Over on the Rx8 club, they said I was crazy. I took my engine apart and found worn flat corner seal springs and a gash on the side of the corner seal, from the sideseal pushing up against it(which is normal in a high milage engine) but my engine only had 14,000 miles when I took it apart. Mazda needs to do a little more research. no excuses for them. with all the money and engineers they have, this is unexceptable!

crispeed

I have to agree with Ito on this issue also. I have also found the same exact problems when using the RX-8 rotors in race applications. The side seals are destroying the corner seals due to excessive side seal clearance. The wear mark on the corner seal is not acceptable for such a short operation time.

From what I've seen the rx-8 rotors are assembled with excessive side to corner seal clearances to what have been the accepted norm form the beginning of the rotary motor. The reason for this might be that excessive clearance is needed due to the design of the motor placing the exhaust port on the side housing thus leading to excessive heat being transfered to the side seals etc. Without the extra clearance side seal growth due to thermal expansion would cause failure. Another reason might be with excessive clearances there is less chance of a side seal becomming stuck form excessive carbon deposits etc. also due to the side exhaust ports. The 'tapered wedge' design of the side seal also helps with that theory also.

The actual problem lies in what is the accepted operation temperature for the side seals to seal properly. If your driving habbits are such that cruising and idling around is the norm would that be sufficent for the seals to seal properly and to resist carbon build up. No one except Mazda could probably answer that question.

Now what I've seen from using the rx-8 rotors in a race application.

Right from the beginning Mazda claimed that the rx-8 rotors were casted using a new process. According to them this resulted in a rotor that was cheaper to manufacture, lighter in design and also due to the more uniform molecule grain in the molding process did not require balancing.

I've not been able to obtain a set that are within the balancing tolerances that the earlier rotors had. Now the rotors are obviously within the balance specs that Mazda considers the norm but in actuality the older rotors were never at the the limit of those tolerances but more important at least the earlier motors had front and rear rotors that were almost identical in weight. Also you cannot lighten rx-8 rotors to same level as an earlier rotor. There's not enough material to do so.

Next problem when using the rx-8 rotors in an earlier application always resulted in lower compression sealing. Compression figures were lower by 20 to 25 psi and got worse after a couple hours of operation. Off course that was due to excessive side seal clearance plus the fact in the beginning the side seals were only available in pre-cut lengths that were too short anyway to obtain proper sealing and compression. After request from racers all around the world Mazda decided to produced the seals in un-cut form. Now I thought that was the answer to the side seal problem but it was not quite that easy.

When Mazda designed the rx-8 rotor they also moved the side seal position more outward placing them closer to the edge of the rotor. That was due to the new port shape Mazda was using in the rx-8 motor. Basically the port timing was opened earlier so the side side seals were moved to avoid them falling into the port. That along with the 'taper wedge' design led to a side seal that could not mate with the corner seal like the earlier ones did. Basically instead of the tip of the side seal butting up against the corner seal, the side seal now would try and wrap around the corner seal placing the sealing edges more on the bottom forming a wedge shape also. You have to visualise that in person to understand it. Without the proper equipment or technique in cutting the side seal to desired length, the shape was not easily obtained if compression was to be perfect as can be. To make a long story short although the longer side seals resulted in greater compression it still could not compare with what was obtained with the earlier side seal design.

Compression with the earlier rotors were in the lower 120's with one piece or upper 120's psi with two piece apex seals. With the rx-8 rotors from the get go compression was around 110psi and after a couple of racing hours would drop below 100 psi and never seem to stabalise and just kept getting lower in the order of a couple hours at racing use would be as low as 80 psi. With the longer side seals compression was up from before in the 110 to 115psi range but the greatest difference was that compression was no longer going away as quickly or at least within a couple of hours of race use. I have not opened the motor with the longer side seals as of yet to determine how they are coping. Any how the major drawback since converting to rx-8 rotors has been the lost of power which in my opinion is due to lower compression from leaking side seals. There are some that also believe that the smaller compression pocket on the rx-8 rotors are also partially to blame for the lost in power but that's another topic that I'm not going to get into right now anyway.

Sorry for the long post but just wanted to state my experiences/opinions using the rx-rotors in a race application.application

Black8

Good info. I always wondered what the rotary would be like if Toyota made them. With their huge resources and awesome reputation for reliabilty, durability and efficency maybe the rotary wouldn't have such a bad rep. But maybe the rotary is inherently flawed and nothng can make it as idiot-proof as a proven piston motor. I love rotaries and belive they are durable and reliable, but only under perfect conditions. They are very intolerant to many things that wouldn't faze an everday piston engine.

1Revvin7

Interesting by all means keep posting...

I8U

I'm one of the ones having issues. My 8 has been suffering low idle with the occasional stall also, I have had powerloss in the upper rpm range but only in the late afternoon. My 8 runs smooth in the morning but the drive home sucks. Had it in the shop a couple of weeks ago for the same problem...I was told it was my coils, they were changed out, the idle got a little better but now it's back to doing the same thing again. I hope it gets fixed this next time I bring it in.