Weights of Counterweights
 

I have looked all over here and on the net and have not found any information about the weights of counterweights front or rear for any year rotary.

Does anybody have this info?

If not then if everybody would help me by weighing their counterweights and posting what year they came off of and front or rear, and also measurements from center to the ID and the OD of the weight and thickness and weight length (side to side), and any markings, then i could make an informational page with all the details.

This would really help for hybrid engine projects for swapping parts for balancing.
for example:

I am going to use S4 T2 rotors (8.5:1) in a S6 block with an RX8 e-shaft and a S4 auto rear CW but the S4 front CW uses a smaller thrust washer and bearing so I heard that I might be able to use a S6 Front CW from an Auto because it is Heavier and 1.6mm thicker?

(engine will be dynamically balanced)

any help?

I suppose that if 2 counterweights weigh the same but the weights are further away or closer to center then this would matter so dimensions are important.

pics would be nice for this as well.

Here is a start for the Rear CW's:
http://www.mazdatrix.com/faq/Rcounterweights.htm


I have a Rear CW for a S6 that has an ACT P/N and a date engraved into it:
04-04-05
P/N: CW01

And I weighed it in at:
4 LBS 0.4 OZ
3 Balance Holes drilled one at the 6 o'clock position and one @ 6.5 and one @ 7.5
(looking from rear of engine or flywheel side)

I also have a Rear CW from a Eunos Cosmo 13-BRE 1990-1995
It weighs:
3 LBS 15.9 OZ
3 Balance Holes drilled one at the 8 o'clock position and one @ 6.5 and one @ 7.5

The Front CW from a Eunos Cosmo 13-BRE 1990-1995 Weighs:
2 LBS 11.5 OZ
1 Balance Hole drilled @ the 8 o'clock position

The S6 Front CW Weighs:
2 LBS 9.8 OZ
3 Balance Holes drilled one at the 6.5 o'clock position and one @ 7 and one @ 8.75 or 9 o'clock

The S4 Front CW Weighs:
2 LBS 12.4 OZ
1 Balance Hole drilled at the 7 o'clock position

All the S4 and S5 Front CW's use the Smaller Thrust bearing and thrust washer (earlier also?)

Both the S6 and the Eunos Cosmo (1990-1995) use the larger thrust bearing and washer.

Please note that although I weighed these on an accurate postage scale that they may be slightly different from yours because of the balancing holes drilled into them.

Anybody else have anything to add?

When I weighed Zenki FC (turbo) versus Kouki FC (turbo) rear counterweights, they were within 0.2 lbs. of each other.
It's pretty much negligible, since my scale resolution was 0.2 lbs. :P
This was on a certified weight scale - 100 lbs. max, 0.2 lbs. min resolution.
It's the kind of scale you see at the supermarket / meat cutter / deli / etc.

As a general rule (at least for FC rear counterweights), the number of holes drilled is a pretty good indicator of what years it came from.
One hole is usually Zenki FC.
Two or more is usually Kouki FC.
If it had 3 or more holes, it's almost guarans Kouki FC.

If you're going to dynamic balance everything, does it really matter?

Side note, Kouki FC / FD / Cosmo 13B are all interchangable, since all those rotors weigh the same.


-Ted

It matters because I don't want any holes filled if it doesn't weigh enough for my setup.
I only prefer to have holes drilled. Know what I mean?
I don't trust it as much and also they charge extra for filling.

Does that mean a S5 flywheel can be used with S4 rotors & front counterweight? Being that the difference between s4 & 5 rear weights was withon 0.2lb?

Or am I missing some fundamental difference like position of weght on the flywheel?
Refering to stock flywheels btw.

No, counterweights need to be matched with the rotors.
S4 rotors -> S4 counterweights / flywheel
S5 rotors -> S5 counterweights / flywheel

The counterweights are drilled on the edges for a reason.
Without getting into a real long discussion which would include college level physics on momentum / derivation and integration of mass / lever moment / centripetal force...
Mass and weight affect a spinning object at the edges rather than the center.

Even though the total weight of the counterweights are almost identical, it's the small holes on the edges that affect the rotational mass more.

Don't try and swap the wrong counterweight / flywheel.
The engine will eat it's bearings in a jiffy!


-Ted

Ha yeah ok then, something like what I was thinking.

I certainly don't want to get into "college level physics on momentum / derivation and integration of mass / lever moment / centripetal force..."

So I'll stick with the "more about the position of the weight" concept.

Thanks Ted.