"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