I was just looking at the mazdatrix website when I decided to look in the RX-8 section. I noticed that the renesis rotors are cheaper that the 84-85 13b rotors. Will the renesis rotors work in a 84-85 13b engine. If so, are they lighter than the stock ones and do they have a higher compression? Just a possibility of gaining horsepower while saving money.

 

my guess is your treading on new ground, I think i heard of mantis having the engines but I dont think anyone has tried parts swapping as of yet.

 

if i'm not mistakin, isn't the renesis just a 13b with side exhaust ports instead of periphreal ports? the renesis is still a 13b. my bet is that mazda is making the engine, thas why they are cheaper. where as our 13b's are almost 20 years old and are "inferior" and so they arn't made is such a high supply. so i'm assuming supply/demand is at workas far as the prices go. but i would think the rotors are the same dimentions.

 

Well, i'm thinking the renesis rotors are higher compression then the others, therefore giving more power, but I could be wrong.

 

Yea, IIRC the compression is 10.0:1 whereas the -SE and 12A ones are 9.4:1. I'm not sure if they would be swapable without a bunch of other goodies; counterweights, stationary gears, bearings, etc. My guess, is that you'd practically have to build a renesis to use them.

My guess is that most of the extra power the renesis engine makes comes from the increased exhaust port area, as well as the varible length intake system that they have.

 

i cant be sure about this but if the compression is higher wouldnt they have to make the rotors wider to keep the same displacement?

 

The rotor width is dictated by the width of the housing and seeing as the Renisis uses 13B size housings the rotor will be the same width. The compression is changed by altering the shape/size of the the recess in the rotor face.

 

What he said. ^^^ The renesis' rotors are much lighter so different counter weights would be needed as a minimum.

 

https://www.rx7club.com/forum/showth...hreadid=209015

 

Remember that displacement is the largest volume when the intake is closed minus the smallest volume when the rotor is at TDC. there is less volume at TDC due to higher compression, but the largest volume is smaller by the same amount. 1 - 1 = 0 therefore no change in displacement.

 

i thought displacement was just volume at BDC? why should the TDC volume affect displacement?

 

Thanks for the info again. I'm just trying to learn as much about the rotary engine as possible. This helps a lot.

 

if you want to learn lots make sure that you check otu the search button and the archives. lots of GREAT info around

 

I was just reading in Car & Driver about the Renesis engine, and how the side exhaust ports increase the power. They said that the reason Mazda didn't use side exhaust ports before now is that they would carbon up to quickly with the oil injection. With the Renesis engine, they control the oil injection at a rate of a quart per 10,000 miles.
So if you wanted to use this engine, you would definitely need to swap in the entire engine management system, intake and exhaust manifolds, or you'ld probably end up with that nasty carbon buildup problem.

 

Premix, atf, mmo, there are many ways around carbon buildup.

 

im still confused about the displacement thing. anyone care to enlighten me?

 

TDC volume does not effect dicplacement, it affects compressiom ratio

 

yea thats what i thought