Thanks Ed, but that wont work. 

 

I only have 1 rear counter weight, and that came with the engine sold to me by Adkins (the other engine came with a flywheel).  Turns out the rotors in that engine were 8.5:1 S4 turbo rotors when they were supposed to be the S5 turbo rotors.  So I have absolutely no faith in what kind of counter weights he threw on there.  There is one for sale on e-bay - but that guy does not know what year it came from either.  hmmm

 

To throw a wrench in the works, I was reading about the subject on the RX-7 forum, and one guy claims that has weighed the counter weights and finds that all engines from 86-95 have the same counter weights!!  But I want to believe it because it would be easy.

 

I know that Mazda has different part numbers but I suppose they could still all be the same...

 

Sigh..... 

 

And the worst part is that there was a pair of 9.7:1 rotors on e-bay a while back and I flaked and forgot to put in a bit...  they went for $120 for the pair, but new ones are $600 each - ouch!

 

I'm taking a good hard look at trying to repair the 9.4 rotors that Ernest sent...

 

Thanks for all the great stats to help me identify the rotors.  The depth seems to match everything else I know about the rotors.  Except:

 

The depth of the chamber on the rotors from Atkins (10.2#  with cast depression) is only (about) 7 mm.  Do you think that the 8.5 rotors might have the same depth as the 9.0 (or 9.1) rotors?

 

Dave

 

On 10/4/05, Ed Anderson <eanderson@carolina.rr.com> wrote:

Dave, a though occurred to me.  Since you do know the weight of the rotors for each compression and year (see Mazdatirx chart below), if  any one had the counter weights for a know year, I imagine there is a proportional ratio between rotor weight and counter weight.  In other words, the lightest rotors should take the lightest counter weights.  Heaviest rotors the heaviest counterweights.  In fact if you had two data points for two different compression rotors you could probably come close to figuring out the third counter weight weight.

 

Just a though.

 

Ed A

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

 

 

Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com