j9fd3s

iTrader: (3)

this may be a dumb question but what does cause an apex seal to break? it seems even in a stock 81 12a they break apex seals (after like 80k), or a ported 13b with a t04. if you can make 500hp on the stock seals then how come they fail at 255hp??

mike

peejay

If you're breaking apex seals in a stock 12A then there's an ABUSE problem. It's generally accepted that the 1st-gen 12As will run for several hundred thousand miles, and only then will fail from just plain being WORN OUT, and only need replaced because of smoking and hard hot starting instead of a "hard failure". (As will happen after 250k++ miles!) As long as you never overheat, drive the engine hard on a regular basis (clans it out), keep the oil topped up and changed regularly, and watch oil consumption (if it doesn't consume oil, the OMP has failed and you need to premix) they're the Energizer Bunny of rotary engines. They keep going... and going... and going...

I know that I just blew one up myself. Factory 3mm apex seals do not like being revved past 8500. Some people say they've revved well beyond that and lived to tell about it, maybe they're just lucky because I sure wasn't. At any rate the engine wasn't stock and it falls into the "abused by owner" category!

Again - apex seal failure is caused by ABUSE. Abuse by overrev, abuse by carbon clogging the seal grooves (as happend with my '87 - the PO never drove it hard and the engine died at only 78k - and it was NON TURBO) and abuse by poor tuning (aka detonation - pop pop BANG). That's another thing - when my engine was first put together I had the timing way off and it detonated well over 50 times (maybe even 100) before I determined the cause and fixed it. Them 3mm seals are TOUGH... ('course it was N/A also)

r0t0rhead

iTrader: (12)

Mazda 3-piece seals were designed for maximum efficiency for streetcars and purpose built by Mazda for best performance under those conditions. Period. 3-piece seals generally develop a "V" wear patterns in the rotor apex grooves when exposed to severe operating conditions such as high boost. For the best apex seal for any nitrous, turbo, or high revving NA engine the BEST & ONLY choice is the Ianneti Ceramic Seals. We've tested every carbon, flake steel, nodular steel, billet steel,& unobtanium apex seal imagineable, and the Ianetti ceramics have ALWAYS outperformed anything else. Don't just take my word for it -call Mazda Comp.or ask any of the other elite rotary race engine builders, Jim Downing, Rick Engman, Darryl Drummond, or Roger Mandeville and ask which seals they use! Cost is relatively high at $1500-$1800 per set depending upon type -but if you can't afford them -you probably can't really afford to do serious racing.

moespeed

I remember talking to someone at Mazda Motorsports last year about this time about the ceramic seals being used with nitrous and high boost.
They said that the ceramic seals did not work well with the nitrous and boost together.
It may have something to do with the ceramics being brittle.
I also remember the prices of the ceramic seals dropping to about $600 per set of 12 tips. You could get any configuration( 3mm / 2mm / 1 piece / 2 piece / 12a /13b).
You may have to be a member to get these prices which is easy to do. If you run you car at a track or plan to run your car you will be able to become a member.
Here is a contact number for Mazda Motorsports : (949) 727-6940 or (800) 435-2508

Also I remember talking to Eamon Hurley of Hurley Engineering Limited.
I was asking him about the fact that Abel is now running ceramic seals.
Mr Hurley has a page with Abel running HME racing seals.
http://www.hurley-engineering.ltd.uk/
Check Seal tips - HME_Longlife_Racing_Tip_Seals.htm
His comment is that Abel is being helped by Mazda Motorsports.(You can't bite the hand that feeds you).
He did note that Mazda Motorsports bought large quantities of HME seals.

j9fd3s

iTrader: (3)

i think i need to ask my question a little better.
while i have seen 12a's with 200+k on them about 80% that i see have had an engine at around 120k. i also have seen a few stock fd's break apex seals. my question is
if you can run 500+hp on the stock seals why do they break at stock boost/power levels?

mike

HWO

DETONATION - normally the combustion pressures int he chamber are say X psi, when detonation occurs you get 5X or maybe even 7X psi, the pressures is the problem.

dont detonate.

peejay

And you have to get extremely stupid to detonate a non turbo engine And even then the relatively LOW combustion pressures inherent in a N/A can be handled by the stock seals. (Talking 12As here)

Probably the reason you saw some many 1st-gens with engine replacements is because the OMPs fail, which causes compression to go away. Funny enough, if you dump ATF down the intake tract the engine will fire right up and run great again, but many mechanics don't know that and just assume the engine's toasted. That's why you NEED to monitor oil consumption, and if it stops consuming oil, you need to either correct the problem with the OMP or pre-mix oil in the fuel.

Another common cause of engine failure in '83-up 12As was the awful oil cooler setup. They'd overheat the oil and the O-rings between the oil cooler and the engine would get brittle and start leaking. They'd leak right on to the heater hoses... which would then get soft and burst. If you're lucky like me, they'll burst while you're already under the hood and you can shut the car off right away. If you're unlucky, it'll happen on the highway and you won't notice anything wrong until you fry the engine. Another cause for engine replacement is related - the O-rings that seal the oil passage that runs through the upper dowel pins also get brittle and leak. The only cure for that oil leak, replacing the O-rings, requires a complete engine tear-down. Again these are in no way related to apex seal failure!