apex seals and why the thickness matters
 

since im new to rotaries i have a question about apex seals...does the thickness of the seal change performance? does it make the motor life live longer? does it change compression? what are the supporting mods for a thicker pair of seals? are thicker seals good or bad for a dd? thanks for the help

This is how it goes base on what "people say"..

a 3mm apex is "thorougher" than a 2mm, but a 2mm seals better than a 3mm, thus supposedly making more power by sealing better.

so you like 2mm seals:Wconfused

damn what the hell did i just wrote??.. anyways

search and draw your own conclusion... this is the never ending battle, i just summarized what many of them threads explained.

I'm personally buying ALS 2mm, they are really impressive

mmmmm.ok 2mm it is then for a perfect balance:icon_tup:

so does a 13bt come with 3mm or 2mm?

13bt is 2mm seals.

I believe that the 13B from the GSL-SE is 3mm.

Going to 3mm seals requires milling out the apex seal grooves of the rotors to support 3 mm seals, you also need 3mm apex seal springs and 3 mm corner seals.

3mm seals are generally only used if your rotors are old and the grooves are unable to support 2mm seals.

ooh ok i see now i thought 3mm was for racing and things of that sort but i understand now its more of a substitute for a oem seal that has groovers that cant support 2mm seals

74-85 13B is 3mm

86-2009 is 2mm

3mm is a little stronger. 2mm is lighter and seals better.

additionally milling used rotors to take 3mm seals is risky, the grooves need to be very exact.

ok got u. man i love learn about rotaries something about them bro thats y ive been saving up for my fd :) i dont care how long and how much for me its a passion and i want my stuff done right and i want to learn how to do most of the work myself cuz for me its passion not just a hobby or sport

im just building a new engine, my first DIY engine build and after a lot of discussion i have decided to go 2mm. half the folks will tell you go 3mm, other half 2mm lol, you just gotta make up your mind at some point and build it :)

i'm going for RA 2mm super seals in s4 n/a rotors.. as j9fd3s has said in dates, anything from series 4 onwards should be 2mm.

some things i read/heard - less rotating friction on 2mm seals - less surface area. makes sense. easier to start maybe because of this. because the seal has less weight, it will be able to move faster, so effectively means your engine can rev higher and it can keep up. i have no statistics on this or how fast a 3mm should rev etc. but it sounds better to me going 2mm.

also the general consensus is not to machine new apex seal grooves (if your 2mm grooves are a bit loose) - expensive and needs to be dead on accurate! - just dump the rotors and find ones with grooves that are within spec.

i think before 1974 they even had 6mm carbon apex seals for racing lol.. things have come a long way.

good luck with your rotary! its an addiction :)

I'm sure 1 mm of mass times 6 is not going to change your rpm's. It more than likely is there's less space for blow by,and less seal to fail. butt thats just my guess.

2mm seals are superior there is a reason the japaneese teams bought up all the stock of the 3 peace seals there is a reason mazda chose on the rx8 to stay with 2mm seals. Not only do 2mm seals seal better but they have less harmonic resence they produce less chatter and have a lighter rotating mass. The rotor grooves on 87+ rotors are hardened milling them for 3mm seals destroys the hardening. The honest truth people pushing 3mm seals just want your money for milling the rotors. Tune the motor properly and theres no need for 3mm seals ever.

From the Mazda training manual for the 2nd generation Rx-7, circa 1986:

https://www.rx7club.com/attachment.p...1&d=1237945552

you can see that all the seals were reduced in width beginning in 1986, in order to improve compression.