Flywhell counter weight
 

I bought a used aluminum flywheel and it came with its counter weight, however the counter weight does not have any numbres or letters stamped on it. Is there any way to tell counter weights apart by weight?

If so, what are the different weights for the 86-88 and 89-95?

Well,

I looked on all Mazda parts catalog, from 86 - 95, and i found the following:

86-88
Counter Weight part number - N327-11-521A

89-95
Counter Weight part number - N351-11-521

For some reason, I am still skeptical :(

ummm those look like the ECU numbers ... but i myself am 100% sure that my S4 88 has a N327 ecu... i doubt the ecu would have the same part number as the counter weight.

There is no way to tell them apart once removed from the mazda factory box which is marked with the part number.

I've inspected all different years of auto ctwts and cant tell any physical difference, unlike front counterweights. I've even weighed them on a digital scale accurate to .01lb and can't find any consistent difference between s4 and s5/s6 weights. I've weighed both stock weights from engines I've parted out, and new in the box weights that came with customer flywheels.

So... you're saying it doesn't matter kevin?

ECU numbers? Most of the stock parts start with the letter N and a 3 digit number. Thats just the way Mazda did it. Its not just for th ECUs.

No, Im not saying that. I am saying that it probably wouldnt make a big difference if you were to use one from a different year, because they weight is so close...within hundredths of a lb.

There must be a distinction between them, or mazda wouldnt go to the trouble of making more than one part. I just havent found out what that difference is yet, and how to detect it visually.

has anyone ever used the wrong year counterwieght?

Maybe its got something to do with the location of the mass relative to center of the rotation. They may look the same shape and be the same size, but maybe has more mass further away from the center of the hole. I'd don't know, I'm talking out my ass.

No, the keyway is timed in the same spot, and the dimensions of the weight are identical. Even the number of balance holes drilled in the bottom is usually the same. And the thickness of the weight end is the same.

Based on what you are saying, and my findings, I am starting to believe that the 89-95 are in fact the same counter weight. The part numbers can be verified by anyone, here:
http://www.mazdaformance.com/rx7.htm

Note - Pages are based by the adobe number, not the mazda catalog number)

89-90 - Page 31
91-92 - Page 28
93 - Page 21
94 - Page 21
95 - Page 20

Now, I am not a mazda parts expert, not even close; but why would mazda use the same part numbers for parts that aren't exactly identical? All rotors, housings, bearings have different part numbers!

This is driving me insane :redface:

thats interesting ... why do i need to get 86-88 auto counter weight to match my 87 rotors when they are actually all the same ...

Actually the 86-88 counter weight is the ONLY one that DOES have a different number than the rest of the counter weights :)

89-91 rotating assemblies are balanced teh same, so that is correct.

The 86-88 and 89-95 assemblies have different weights, so they should be balanced differently. And indeed there are different PN's for the 2 rear weights. But, I can't distinguish any physical or weight difference between the 2 parts. That's what we're discussing...the difference between s4 and s5/6 weights.

well the 86-88 rotor weight the same, and then the 89 and up rotor weight the same

Ohh my bad :redface:

I was told by somebody at RB this morning, that S4, S5, and S6 were all different, hence my investigation. All in all, I should be ok, since I have a S6 counter weight going in to a S5 engine.

Thanks :bigthumb:

I bringing this back...would like to know more...I've been reading that you need the counter weight from the correct year; but now we're saying that things seem the same? So, I would like to know if the weights need to be the from the same year or not...I'm so confused now!!

I personally wouldnt take a chance, and would buy the correct part for the year of engine/rotating assembly you're working with. I'm just saying that I can find no difference between the 2 parts in my own physical inspection. Take that for what it's worth.