So what's the deal with 2mm versus 3mm apex seals ? My 13B has the 3's. Please 'splain it for me.

 

All engines '74-85 had 3mm.

'86-02 had 2mm.

'04-up have "short" 2mm.

There you be.

 

2mm are very tough and cause less friction and housing wear.The 3MM are even stronger in an abusive situation(detonation,ragged tuning),but can cause more wear to the housings since they have more contact area.
If your turbo engine is tuned correctly and you dont flog the living crap out of it,the 2MM seals work fine.I push mine to 14psi all the time.John at Mazdatrix talked me out of the 3MM seals for my S5 TII engine,just not needed for a 300-400hp streetcar with proper tuning.N/A cars dont really need 3MM seals,since revs are more important than detonation resistance.

If you have a 12A or pre-86 13B,your stuck with the 3MM seals.Not a bad thing since they are tough,but Mazda made the 2MM seals standard in 86-up cars because they were more effecient/lighter.

 

2mm are strong enough. People have broken side housings and dowel pins and caved in rotor faces and left the stock Mazda 2mm seals intact.

2mm are superior. I haven't pulled apart an FC engine that had marked housing flaking or heavy chatter marks, even after a couple winds around the odometer. 3mm seals however can really do a number, if not severe chattering then heavy duty flaking. It seems that FC housings only die from FOD (waiting for a seal to come apart before rebuilding) or from corrosion (not changing coolant every other year OR WORSE running just straight water)

 

True,plus the 2nd gens have direct oiling and micro-pores in the chrome,both of which help prolong housing life.

 

AFAIK *all* rotaries, from '74-on at least, have "micro pores" in the chrome.

I'm not so sure that the direct oiling makes a difference as far as engine life is concerned. Its main purpose was to reduce the amount of oiling used in the first place.
Newer rotaries use FAR less oil than carbed ones do.