So I bought the three piece apex seals. Should I return them and why? S5 n/a rotors, streetport. daily driver and autocross.

 

are they new?

 

Yes, brand new.

 

3 piece seals seal better, slightly.

did i miss the memo that mazda went back to these? my friend bought new seals last month and got 3 pc ones too.

that's too many sets to be old stock, as there was like 6 months of NO apex seals when mazda switched

 

Don't be surprised if Mazda goes back to 3 piece seals on whatever new engine they are working on. They switched back from 3 piece to 2 piece right around the time the Rx-8 came out, and Rx-8's had a 2 piece seal with different dimensions than the older engines.



The advantage of the 2 piece seal is that there is just one less piece to break, and that's more of a concern on turbo motors.

 

Ordered mine 1/5/2010 and got the three piecers.

 

Crap. I'm not happy at all that Mazda switched back to three piece seals. True, they seal a bit better. But also true is that they are less reliable then the older 2 piece seals because they are less tolerant of wear. The three piece seals are probably the reason for the decline in engine life from the older 12As/13Bs to the second gen 13B. Old 12As and 13Bs ran forever, until 3 piece seals were introduced.

 

their rendition of gas leakage is also a bit overdone. 2 piece seals are superior. 3 piece seals also wear much quicker as they get worn and can cause issues even in non turbo applications. 2 piece seals make just as much compression, the same if not less carbon buildup on the springs and in the groove and are much more durable as well as less likely to trash a rotor and housing if one breaks.

 

****. Well 20% restocking fee + shipping and 2-4 months to get a credit don't sound like a good financial decision. So I'll put in the three piece apex seals. Karack et al, what is the typical lifespan of the 3 piece apex seal and at what mileage should I tear it down before it breaks?

+ Can anything be done to reduce carbon buildup on the springs? Would Seafoam help?

 

typical lifespan is about 130k before they start to thin out and start to wear rapidly on the sides of the seals(however some have been known to go well over 200k, it depends on how you drive) which also makes them more fragile and susceptible to fracturing in boosted applications. i just prefer to not use them because in case of detonation they are more likely to crack in the middle of the seal into many small pieces instead of tearing the end of the long seal off and spitting it out the exhaust.

brand new they will last a while before you should worry about them but for the reasons above is why i prefer to not use them.

to decarbonize the internals i either use tons of water ie a water treatment or use carburetor cleaner. i stay away from seafoam and ATF because some cars have catalysts still installed and i don't see those products being "cat safe" in a rotary engine environment. just be sure to inject enough to bog the engine down to just barely stalling or it really is doing next to nothing. it's a good idea to decarbonize an engine about every 15k miles.

 

It's a 20+ year old car. You're not going to be driving it that much anyway, I wouldn't worry about it. Just use the seals.

 

i've seen the 3 piece seals go over 220k miles and not just once. usually at that point the 20+ year old motor is using a ton of oil, and some water....

they don't need any different care or feeding than the 2 piece seals.

and BTW ive got a broken 2 piece seal engine here, they might be a little beefier, but the triangular part still breaks first

 

Or a 35 year old REPU. Thanks guys, I'll install them. Hate to put a design flaw in the motor but >200,000 miles is good enough for me.

I did break a 2 piece 3mm apex seal in the heavy 74 13b rotor back in 2002. Overrevved it many a time and driving one day the motor just seized. Now I have a rev limiter and a 11.5lb rotor with neat gouges. And a story.

 

I've got a set of apex seals from a 140k mile block. Happy to share that the rotor slots are still basically like new. And the apex seals have worn down to nearly the minimum thickness of 6.5mm. Amazingly all springs are even still in spec. I'm using new 3 piece in my build.

 

I'll be building an engine for my Cosmo with GSL-SE 3MM rotors soon, and you can bet I'll be going 2 piece Atkins. I'd rather go aftermarket 2 piece then OEM 3 piece.

 

^^ go with super seals ^^

 

I thought Mazda never made 3 piece 3mm seals anyway? The old OEM 3mm's were 2 piece. In a modified turbo engine I'd rather have 2 piece but for an n/a engine might as well go 2mm 3 piece if that's what Mazda is making now. They do seal better.

 

i don't think they ever did, and i still dislike the 3 piece seals because they shatter towards the middle of the seal usually.

 

3 piece seals work good..............for apex groove & coolant seal groove scrapers!!

 

true that, i have tons of scrapers!

 

The stock seals are 3 piece and they have always worked just fine. I personally prefer 2 piece seals when building an engine but don't be upset that you have 3 piece. Just use them and don't worry about it. In the real world you are not going to see one bit of difference in wear or power. In a lab you might.

 

question out of my own curiosity....

are all three piece glued together in the factory package? If not that would be a huge PITA

 

And that's a good point, forgot about that one! All pre-86 seals were 3MM and 2 piece. Hm, perhaps that's why those engines ran damn near forever? Not the 3MM, but the 2 piece design.

 

Ha! by that logic, Rx-8's would go 200k easy with their factory 2 piece seals. of course having a crappy OMP doesn't help

 

it does make a big difference in high horsepower forced induction applications for the reason i mentioned in my last post. of course this thread isn't about that type of build but some people read things into what is said and accept it as universally true. the 3 piece seals have also been known to fall out of the apex seal grooves when they get severely worn, which isn't a problem that the 2 piece seals have. the 3 piece seals work just fine for near stock applications but even moderately above that the 2 piece seals are far superior in saving headaches when any issues arise as well as the cost of a new rotor and housing in probably around half of the seal failures.