I finally took apart my JDM engine that I had, and I became dumbfounded when I saw the apex seals on the rotors. At first when I saw one of them drop out, I figured that the engine was blown and the previous owner lied to me (which I didn't care much since I'm rebuilding it), but after close examination and seeing that the big part of the apex seal was cut in a very precise horizontal fashion, I had no idea on what to think. I checked out the other apex seals, and they were all like that. Instead of just two pieces (the small edge piece and the long piece), there's three pieces (the small edge piece, and the long piece is cut horizontally into two equal size pieces). Can somebody please let me know what I have in my hands and if these type of apex seals are better than the regular two piece ones or not. I'll try to get some detailed pics tomorow, but I was thinking that before then maybe someone has seen these before and knows a bit about them. Let me know ANYthing that you know about this three piece type of apex seal. Thanks beforehand for everything guys....
-Erik

 

Those are the original apex seal design for 1986+.
Yes, those are stock Mazda OEM.
Mazda changed to a 2-piece design a few years ago; any new apex seal you buy from the Mazda dealer should be 2-piece.

The older 3-piece design sealed better - due to all the sliding surfaces.
The newer 2-piece design is stronger, due to not having that thin piece that slides over the rotor housing surface.
So each has it's advantages and disadvantages...


-TEd

 

so which one would you recommend for me to use? the apex seals are pretty much brand new with nothing wrong with them and no scratches or wear at all. thanks for the help dude....
-erik

 

If the seals are still in spec, you can reuse them but they need to be installed in the same spot they came out of. Personally, if they are more than 1/3-1/2 way through thier wear limit, I would replace them. Others may disagree on the wear limit but I prefer to be safer than sorry later.

 

yeah i know what you mean about the being safer than sorry since i'm going to be selling the engine with a warranty on it too, but i want to know which type of apex seal would be recommended to use on the rebuild. the three piece or the regular two piece? which one outweighs the other; better sealing or a stronger apex seal? thanks for the feedback trochoic....
-erik

 

Use the current 2-piece design.
It gives up slightly in sealing to give you a lot more strength.
This is especially advantageous when running significantly more power than stock.

BTW, IIRC, specs on stock Mazda apex seals are...
8.0mm = new
7.5mm = change (short?) apex seal spring
7.0mm = max wear limit, change to new apex seal

So, 1.0mm of wear is the Mazda spec to change them out.


-Ted

 

hey man, i can't thank you enough. good luck with your car, and thanks again reted and trochoid for the info....
-erik