I have tried searching but have found no info on this. I need the exact weight of a S5 rear counterweight. I have two rear counterweights but I do not know what they are off of. They are not marked from the factory. One weighs 4lbs 1.6 oz and the other weighs 4lbs 0.6 oz. They are shaped the same. I have found the specs for a S4 rear counterweight and it list it as 4lbs 1.5oz. Since I can not find the specs for the S5 or S6 (which should be the same) I do not want to use the other counterweight untill I am 100% sure.

Mike

this is for a 3rd gen and ACT flywheel

 

anyone?

 

wouldn't the weight of your front counter weight need to equal the rear? Just thought I'd throw a guess out there.

 

FWIW, 89-95 rear ctwts are the same, because the rotors are weighted the same.

I've worked with 84-95 rear ctwts for years in building engines. I've also tried to distinguish between them once removed. They all look IDENTICAL. I've used a digital scale accurate to 0.01lb to compare them. I can find no more than 0.05lb difference between any of the 86+ counterweights I've tested...some off original automatic engines, some new in the box from mazda that accompanied an aftermarket flywheel.

FWIW, the weight of the rear ctwt for 89-95 is 4.02lb according to my measurements.

 

Kevin, WOW! are you really sure???

They have different part numbers and go with rotors that weigh different amounts. I can't immagine that they are all the same (but good on you if you have really been weighing them). I wonder why MFilippello found some that appear to be different weight.

 

Also, what about the front counter weight?

 

Here is info I have compiled from my personal obvservations of many hundreds of engine teardowns. I have it in graph form but that may not translate here on this forum.


84-5 GSL-SE
86-88 Nonturbo
87-88 Turbo
89-91 Nonturbo
89-91 Turbo
93-95 -rew/-re

Rotor Compression ratio
9.4:1
9.4:1
8.5:1
9.7:1
9.0:1
9.0:1

Rotor apex seal width
3mm (w/thicker side seals)
2mm
2mm
2mm
2mm
2mm

Rotor weight 11.5
10.5
10.5
9.5
9.5
9.5

Front ctwt 3.0
2.7-2.8
2.7-2.8
2.6-2.7
2.6-2.7
2.6-2.7

Rear automatic ctwt
4.2
4.0
4.0
4.0
4.0
4.0

Nonturbo small flywheel
25.8
23.9
N/a
20.7
N/a
N/a

Turbo large flywheel
N/a
N/a
27.4
N/a
22.3
20.3

 

Kevin, the weight of 4.02 lbs = 1823grams. i finally found some info that the 89-95 should weigh 1820 grams so this is right on target. My trip to the post office yielded 4lb .6oz. this equals 4.04lbs or 1833 grams. This is 10-13 grams heavier than spec.

The other counterweight weighed 4lb 1.6oz. This is 1860 grams. From that same thread I obtained a spec of 1855 grams for a S4 counter weight. This seems to be dead on, only 5 grams difference.

So one conterweight is 5 grams out of spec and the other 10-13 grams out. Using your spec of 4.02 and adding a .05 deviation as you stated the highest weight you recorded should be only 4.07 lbs. This equals a total of 1846 grams. This is under the spec by 9-14 grams.

I guess it gets hard because you can possibly have a light S4 and a heavy s5 and they will be close to each other. What would you say was the highest recorded weight? I definately see a difference of 1oz or 28.35 grams. One ounce might not seem like a lot but the difference in spec to spec is only 1.2 oz anyway.

Unfortunately the S5 conterweight I have has wear around where the rear seal lies. I don't think I will use it. Any of those perfect 4.02 lb counterweight lying around you want to sell.


mike

 

I dont remember any rear auto ctwt from 86+ weighing more than 4.06lb, I believe they were mostly all 4.02, with maybe 1 4.01 and a couple 4.05/4.06.


Just as with rotors, yes. Even though a ctwt came from an s5/s6 rotating assy, it could have been a set of A or B rotors which are heavier than D or E's, and thus the weight is slightly heavier. None of this is exact, there are tolerance ranges set by mazda and as long as weights fall within certain classes, they are deemed okay, they do not have to match.

This is why some pay big bucks to dynamically balance their rotating assemblies.

I dont have any auto ctwts laying around right now, sorry. FWIW, the line in the rear seal surface is common, and should not affect sealing.

 

I believe my rotors are C weight, do you think I should be ok using the CW I have that weighs 4# .6oz?

Also, when you order a factory Mazda CW through the parts dept, do they come with any holes drilled in them. It would seem that they would be blank, so to speak, and then they would need to be trimmed to match the rotors in a particular engine. I wonder what a brand new counter weight from Mazda weighs?
Do you know if Mazda balanced each assembly when they built them new. If so then the counter weights from each engine should be slightly different as you have observed. If this is the case then how come Mazda doesn't sell CW's that go with certain rotor weights.

I'm probably over thinking this, just my **** side coming out.

Mike

 

This may help a little to sort things out.

There is a difference between the S4 and S5 front counterweights that is easy to identify.

Attached is a picture of the two Front counterweights that I have, and as you can see there is a visible difference in the width of the flange. Unfortunately, I cannot remember for sure which is which, but I believe that the thinner weight is from the S5 (89-92) engine. This would make sense as the s5 rotors are 1/2 pound lighter.

I measure the thickness of the weight at 1.024" on the Series 4, and 0.920" on the S5 counterweight.

Can anyone verify these dimensions? How about for the rear?

My other dilemma is my rear counterweight - I don't know which one I have. Assuming Mazda used a similar method to change the weight on the rear end there may be a measurable difference there as well.

Mine measures 0.550. I am hoping it is for a series 5 rotor. Anyone have one around that they can measure?

Thanks,

 

We're discussing rear auto counterweight differences. Yes, the front ctwts are thinner as the years go by, for the lighter rotors. This makes them easy to identify. The rears, however, are the same thickness and almost the same weight.