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Note: this is about N/A applications.



I believe the combustion chamber is such a bad shape that it may be detrimental to performance when using the rotors in an earlier engine. Sure they work well in the RENESIS engine but that doesn't mean they will work well in other applications, the RENESIS has a lot of different characteristics including 2 psi of manifold pressure due to the intake design. This in itself could make up for the poor combustion chamber shape. The RENESIS was designed for, among other things, emissions and fuel economy. Higher compression ratios help with these points but doesn't necessarily mean higher hp (in this case anyway I think).



Points to consider:

1. Squish is improved.

2. Flame speed may be reduced due to shallower combustion chamber.

3. Engines ability to draw in intake charge is reduced due to smaller chamber volume.



Please correct me if I am wrong, this is how we learn.



I know of a person who lost 30 odd hp when they changed from S5 n/a rotors (9.7:1) to RENESIS rotors. They are also running methanol which ofcourse is a slower burning fuel and I believe would be more succeptable to poor combustion chamber shape.



I have not found anyone who can honestly say they are making more power with RENESIS rotors than with earlier types, most seem to be making less hp. S5 rotors definately work well and are widely used so why don't the RENESIS rotors with only .3 difference in compression??



Ideas anyone or someone know someone making more hp?

crispeed

We are going to try one more time with the rx-8 rotors being that un-cut side seals are now available from Mazda. Side seal leakage was the main drawback in our experience.

RONIN FC

I agree, I think the bump in compression was done more to help emissions. But the Ren rotors are lighter and cheaper and thats a big motivation for some to work with it. (and maby the novelty)

j9fd3s

well they are like 1/2 the price of s5 na rotors, then its lighter, and higher compression on top of that, it seems like a good thing! if they just dropped straight in, life would be grand

ColinRX7

If the RX8 rotors were that detrimental to intake charge from the smaller chamber volume, why isn't everyone running TII rotors for big overlapping N/A applications? Perhaps then the N/A rotors are too high as well if something is to be gained for intake charge?





Not trying to be facetious, just thought the smaller chamber volume of the RX8 rotor affecting intake charge was a bit like splitting hairs.. Is it really that bad?

Nospig

Using rx8 rotors in 13pp (factory housing) altronic ecu 55 mm TB couldnt make more than 290 FHP. Tried different exhaust set ups etc. Rebuilt using hi compression s5 rotor all else the same and tuned extra 85 FHP.

Nospig

Not sure but rx8 rotor housings may have plug spacing different from s5 NA engine, as s5 turbo housings are different . And factory pp housings have the same plug lay out as s5 Na. And it dose make a difference!

RONIN FC

Maybe... No one can claim any gains as of yet. And add this to the equasion, the Ren rotors are higher compression with bevels in the rotor. The "tub" must be greatly compramised.

crispeed

We basicaly experience the same problem but most of the lost was due to side seal leakage. Compression with the Rx-8 rotors could never come up to what was the norm with the high compression s5 rotor.

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What octane fuel were you using? Did you try low octane?