Anyone know a company that makes them or modifies them?

I'm wondering if in my future (race only) N/A FC I can have 11:1 or 12:1 or so rotors put in it.

Worst case I was thinking (although I have no clue if this would work) of taking a rotor and welding on some extra material in the dimple, then grinding it away as necessary, leaving an equal face on all three faces, and raising compression.

 

RX-8 rotors

 

has anyone tried this yet? its still a 13b right? thats waht it says on the side of the rx8 motor..

 

RX8 rotors won't work.

I've thought about that...it was an idea I got from racing go carts...

We would pull apart our little 5.5hp briggs motors and run a bead of JB weld across the top of the pistons to up the power a bit...sometimes we'd weld a couple beads down or JB some pnnies to the top. The problem tends to be whenyour bead fails or when the JB racks or something. I've heard said that a 13b is a lot more of a PITA to tear down and rebuild than a briggs motor.

However, I have contemplated MANY times going to the local welding shop and having them run a bead in the dempls. A pro could weld a bead strong enough to fully bond...the problem you're going to encounter is keeping everything even. You might end up with a 9:1 compression on one face, 9.3:1 on another, and 8.9:1 on the third...see what I mean? You have no way of making it even.

 

Why will RX-8 rotors not work? did they change (cant think of the word.triachriatnvdkjdfhk) how the rotor spins on the eshaft?

News to me.

 

RX8 rotors have no effect in performance. I'm not well versed in it. Mark can explain it.

 

Um, they are higher compression.....so they are what he asked for.. i'm confused on why they don't work...


Mark?

 

They've been tested and yielded no gains. Sorry.

 

One of the big companies (Mazdatrix maybe?) tried them in an engine and they didn't net any real gains.

 

Also, the RX-8's 9.0:1 compression ration is no higher than the S5 N/A's 9.0:1 compression ratio.

 

I thought they were suppose to be 10:1 or 11:1...eh.. guess i was misinformed

 

The S5 NA is 9.7:1. There was a thread with a guy claiming to use 10.1:1 rotors, but I've never seen them for sell.

 

RX-8 uses 10:1 compression rotors.

 

intead of getting higher compression, just cram more air and fuel in there. same effect.

 

rx-8 rotors are 10:1
they worked and there was gain on it, try www.ausrotary.com
i thought about that idea, but thought into it more its not worth the work

 

Mazdatrix tried the RX-8 rotors in their race engine, and they said you had to reverse the front and rear rotors. The catch, they made just as much power with the stock s5 rotors. They say it's not worth the cost or the effort.

 

Nother thing about modifying your own rotors is the fact that they need to be balanced. So if you weld a bit of metal in the pit of the rotor, it will have to be perfectly centered and perfectly even to that of the next two faces.. I bet if it isn't, you'll get some eccentric shaft wearing and engine vibrations that you don't want.
It is the eccentric shaft that the rotors run on right

 

FWIW, the motor that mazdatrix built with Rx8 rotors was down on power. But they ahd to rebuild it and decided to use S5 na rotors. And they still were down on power, so their testing isn't done.

Quite a Few ppl in Aus. and NZ have used the RX8 rotors and got about 20hp from using these rotors. Also the RX8 rotors are 10:1 compression wise.

And lastly Barwick there was a discussion(sp) about his in the rotary performance section, no one ever tried it, but it was taken as a bad idea. You can call Downing Atlanta, Jim Downing would be one of the only ppl that would have experience with this. http://www.downingatlanta.com/

 

higher compression usually means more power so im confused that running 11:1 rotors would down power, however comparing rx8-series5 rx7 dynos, youll see they both make just about as much power as the other. id be fairly sure that increasing compression should yeild more power.. and higher octane requirements.

 

People other than mazdatrix have seen gains with the rx8 10:1 rotors. There is some controversy as to weather the rx-8 apex seals are up to the task of corssing PP exhausts, some pople mill them to the older depth. Mazdatrix had good results with ceramic rx-8 sized seals. you donw waht to up the compression much more thne 10:1, much higher then that and the trochoid of the housing starts splitting the air fuel charge into two seperate chambers and you get a crappy burn and less power.

 

The aussie who got gains with te RX-8 rotors in his peripheral port engne was comparing them to the 9.0:1 cmpressions rotors he was running previously. Of course he gt more power. Mazdatrix showed no gains from the RX-8 rotors vs the 9.7:1 n/a rotors despite being lighter as well.

The RX-8 rotors cost about half as much brand new. You need to use the Renesis seals on the sides. The corner seals must be previous seals though as the Renesis corner seals will absolutely destroy a 13B housing. You also have to mill out the rotors a little so that the older 13B apex seals can be used. The Renesis seals are not as tall. The stress of them over the peripheral exhaust port causes them to warp and ultimately break. You also do not use the cut off seals and as mentioned already, you run the rear rotor in front and vice versa. This is alot of work and in the nd probably isn't any cheaper than buying new 13B rotors.

The reason why the Renesis rotors don't make as much power comes down to the seal clearances. The Renesis uses side seal clearances that are 4 times the max allowable for the 13B. You get alot of leakage. this was done by Mazda since the side seals see the heat of the side exhaust ports. They account for seal expansion with larger than normal clearances. It is far easier to just use 9.7:1 rotors.

 

That wouldn't be too much of a problem to work out with the right tools and the right guy doing the work. Like I said, grind them down till they're equal.. To do that you could do any number of things... somehow determine volume of water on the rotor face, use clay molds, anything...

 

I would, but the racing officials would probably notice a big giant turbo hanging off the side of the engine.

 

Another thing someone mentioned is the shape of the dimple causes either better emissions or better power, or just generally changes the characteristics of the motor, depending on the shape. Anyone know about this, I heard there was an SAE article on it.

 

www.racingbeat.com

http://www.pineappleracing.com/

You asked if anyone makes or sells modified high-compression rotors, so here's two companies that make lightened rotors. Sorry, but you're going to live with a 9.7:1 CR.