"Why are  you thinking of running the RX8 rotors  for?
The compression?
The  bevel?

The reason for considering  the RX-8 rotors was to increase the compression
ratio to 10:1 and the RX-8  rotors are lighter.  I have a set of 9.7:1
rotors that I was  considering using because they were cheap, but I want to
confirm what I  have before putting them in.  Unfortunately, I lost the info
that I  used to have to told how to tell all the various rotors  apart.

Don


Here are some old messages Don.
Paul  Lamar

Old  messages:
==================================================================
Hi  Paul,
I'm enjoying following along with your current threads!!
Hope you  don't mind me chiming in here again to ask another  newbie
question:

I've been slowly acquiring S5 NT (9.7 : 1) rotors  for my 20B NA
project
(much cheaper that RX8 rotors).  I had 2, and  just received the
3rd one
today.  I've been trying to be careful to  make sure I get rotors with
matching weight code stamps, but the one I got  today is
different.  Can
you help here?  I hope you don't mind  me including pictures!!  I
tried
to make the files small.  The  first 2 pics are the rotors I
already had,
and they show a "C" along  side another weird symbol (kinda looks
like
a 7).

The next pic is  the rotor I got today.  It shows a "C" along side an
"E" :
My  question is.......Is it OK to use all these rotors together?   Are
these all S5 (9.7 : 1) rotors?  Is this last rotor a weight  code
"C" or
"E" ?  What's the other symbol of Letter  mean?

Thanks again for all your help and knowledge!!
Don

From  what I gather you can't mix and match weight codes.

I think you need to  have it balanced by an experienced
rotary engine balancer. The rotors must  be balanced
about their center point and matched with all the other  rotors
for weight and then the counter weights adjusted
for the exact  weight of the rotors. There is a guy here in
So Cal that does  it.

Rotor weight codes.
The only thing I can find is  this.
http://www.rx7club.com/showthread.php?p=1309602#post1309602-

I'll  forward this to Jim Mederer. Hopefully he will have time
to help as he gets  the really hard questions :)

Paul Lamar ...No rotor no  motor.


Hi Don;

These all appear to "C" weight rotors.   For a 2-rotor, letter codes must
be adjacent,
e.g. B/C, D/E, C/D are  OK  (A/C, B/D are NOT)
The rotors themselves are balanced about their  centers at the factory.
I am not sure what the balance requirements are for  a 3-rotor.
I believe the backwards "E" and other characters are Japanese -  don't
know what they mean.
Theoretically, the S5 rotors weigh the same  as the 20B rotors, and you
"should"?
be able to use the 20B front and  rear counterweight without rebalancing.

I posted some rotor/balance  info a few weeks ago.
The S5 rotor faces are machined, the S4 have a rough  cast appearance.
You could also measure the depth of the combustion  area.
See attached file
- might be worth adding to the  website.   I don't have any turbo stuff.
A couple of housing  comparisons might be useful as well, I'll see what I
can scare  up...

When mixing and matching parts for higher than stock rpm, a  custom
balance is not a bad idea.

Cheers
Cary


Thanks Cary,
This is what I have:

All are machined  faces.
Thanks,
Don
Hi Don;
The S5 NA  rotors are at a bit of a premium for racing and higher
activities :)
Worth a quick depth check on the rotor recesses to ensure they are all the
same.
Personally, I would run the stock 9.0? 20b rotors in NA mode  for the 5-8%
HP loss.
If you have the room under the cowl - you  could re-add a turbo later.
Just curious, what is your  project?
(Sorry if I've missed it, I don't read all the  emails)

Cheers
Cary

Hi Don;
Also meant to  ask if you have removed and replaced the stock 20B exhaust
sleeve  inserts.
I have heard they are quite restrictive and many people replace  them
with 13b turbo inserts.
Although removing them is a good way to  break taps...
Cheers
Cary


I also ran across this information on the Mazdatrix website:

_http://www.mazdatrix.com/r-rtrwgt.htm_


Don


Rotor Weight and Compression  Chart
____________________________________

This chart is included in our Website for reference purposes. The  weights
listed are for production, unmodified rotors.

Engine Year Compression Weight (Grams) Weight (Pounds)

12A  76-82 9.4 4603 10.15
12A  83-85 9.4 4353 9.60
13B 74-78 9.2 5253 11.58
13B 84-85 9.4 5253 11.58
13B N/T 86-88 9.4 4553 10.04
13B Turbo 86-88 8.5 4553 10.04
13B N/T 89-92 9.7 4328 9.54
13B Turbo 89-92 9.0 4328 9.54
13B T/T 93-95 9.0 4328 9.54

NOTE: Weights are approximate, and include rotor bearing, but do not
include any seals or springs.

Don