[TECH] Measuring APEX SEALS (with pics)

[-xlr8planet-]

Tools


Brand New 12A 3mm apex seal


Old Used Apex Seals


Notice the difference in the triangular piece.



First we ID the seals


This is what a brand new apex seal should measure


Old Apex Seals. Limit is 7mm. These are all within spec






Notice the difference in height?




Reference material




Hope you guys like the writeup


Oh, and NO, I dont own a micrometer

[WE3RX7]

Nice pics. I was thinking to myself before I saw the measurements that your old seals looked to be in decent shape. As Kevin said, I wouldnt have reused them either unless it was a race engine or a quickie job - but not something you'd want to run down the road for a few years.

Very nice pictures too - your camera works better than mine!

[WE3RX7]

Oh and about the triangle part - is it designed that way to endure more stress? At the angle its being pushed on, I can see why a curve is harder to break - but does that mean it will also hold more compression for a longer period of time.

Since they are factory mazda seals, is that curve just a design change since the years have gone by? Your old seals look like factory. I think thats awesome for mazda to go back and redo a design for a seal used in an engine not produced anymore...

[-xlr8planet-]

Also if you look closely, the lil top the spring pushes, its smaller on the new seals

[WE3RX7]

^ Well damn - I thought it was something more technical, lol. Still a good point though although I've never had issues putting seals and springs in before. I do flip the seal though for BP engines...

[Jeff20B]

The GSL-SE has such good oil injection that the seals will wear far beyond the limit of 7mm to th epoint where they break at around 5.5mm or so. If you can catch it before any of them break, there is a good chance the apex slots in the rotors will be in great shape. None of that slot widening you get with 12As and early carbed 13Bs with their inferior oil injection into the carb. By the time those hit 7mm, the apex slots are usually quite wide and require a new rotor or careful tapping of the tips back together, which is not a very good idea.

[-xlr8planet-]

Originally Posted by Jeff20B

The GSL-SE has such good oil injection that the seals will wear far beyond the limit of 7mm to th epoint where they break at around 5.5mm or so. If you can catch it before any of them break, there is a good chance the apex slots in the rotors will be in great shape. None of that slot widening you get with 12As and early carbed 13Bs with their inferior oil injection into the carb. By the time those hit 7mm, the apex slots are usually quite wide and require a new rotor or careful tapping of the tips back together, which is not a very good idea.

the slots on the rotors I took this apex off were in great shape. even the oil control o-ring carriers showed minimal wear

[-xlr8planet-]

Originally Posted by RotaryResurrection

Yes, the 1gen oil injection delivered a much higher volume of oil than the later versions. In fact the problem with rx-8s needing engines at 50k miles or less, comes down to a lack of OMP injection volume. They simply turned it down too far in an effort to pass emissions and rid the rotary of it's oil burning reputation. Now the seals are warping and wearing out prematurely.

Too bad the 1gens had shitty rotorhousings that started chrome flaking in 50-75k miles and caused compression loss and blowby. The coating on the rotorhousings grew stronger with each generation of engine so the later year models wear a lot less and do not flake as heavily.

I think I will have better luck using JHB rotor housings and OEM seals.

[spankle my wankle]

this is some good info here....