Why do the apex seals break so easily. It appears they are pretty well supported on the sides. I can see that lack of lubrication would cause excessive wear but don't see why they break. Detonation I suppose can blast about anything apart but even then it seams like the metal used for the seals could be engineered to take more punishment.

 

welcome to the board.

break easily? i'll give this a shot ...

it might be hard to fathom and actually conceptualize, but if you really stop and think about it, they are pretty amazing. they take a hell of a lot in their lives:

- separating combustion pressures without any aid of a physical barrier (cylinder wall, head gasket, head)

- living in insane temperatures under normal conditions, but especially when forced induction is involved

... and in the event of detonation, those little 2 to 3 mm metal, carbon or ceramic (or 5 mm carbon) seals are fighting the same forces that break ring lands, bend rods and sometimes just outright melt or shatter pistons. does that give some perspective?

finally, on the subject of engineering them to take MORE punishment, it can obviously be done. many aftermarket seals take that approach. however, it is done without the regard for engine longevity - something that Mazda, as an automobile manufacturer, had to take into consideration.

 

If you're new to the rotary but have some mechanical experience, this is a great book (IMO) to get you up to speed with the basics....
Reads easy and with alot of diagrams and pictures. I think it'll answer your question about pre-detonation alot better than I could...probably anyone else here given the format limits. I think it's particularly helpful to the new FD owner for a number of other reasons.
I also found this thread (Post #6 and on) which is about the best explanation I've seen here....... https://www.rx7club.com/3rd-generati...ragile-191510/ I think it also explains why side seals are generally more insulated from detonation damage.

On a side-note....I'm in Bellevue and your screen name seems familiar. It's been a few years, but are you on the local SCCA forum by chance? Maybe from local autocrosses?

 

the OEM seals are mainly a cast iron material with some treatment processes done afterwards to improve wear characteristics.

this material was chosen because of the wear characteristics and the fact that it is the most resistant to heat warpage.

this works fine for most stock applications and might even be more desirable from a manufacturer standpoint.

 

Thanks for book suggestion. I am new to working on Rotary engines so will need some good foundation information. And yes I am in the SCCA. Have been building and driving a Porsche 911 for many years. Have done all the work on that car myself including body, engine, transmission, suspension really nothing on the car I haven't into.
I apologize a bit for the post as pretty much knew the answer but you have to build your post count to even view many of the forums. I tried to come up with a question that might be of interest and it was. I didn't realize there multiple choices of materials already.
The car I will likely get is a 93 with a full strip down repaint, the motor built by Pineapple racing with a large street port, the turbos are from a 99 japan car, the waste gates were ported, the fuel system was completely upgraded has a new medium duty street clutch all this was done after an engine fire. There are still multiple issues with the car. From what I understand mostly electrical. I am guessing bad grounds and I also understand that there is some issue with the MAP sensor and the secondary turbo does not come on. So I will need to learn fast.

 

I suggest downloading the Factory Service Manual from the FAQ stickys or finding a hard copy to buy. You might also scroll down to the links for BUYING a 3rd Gen. There's a wealth of free info in those FAQs but it will take a while to get up to speed.
Owned mine for nearly 11 yrs, before that had an FB... and I'm still learning.

 

I will definately download the manual. I will be needing it to trace out the electrical gremlins.

Also do you happen to have the silver FD with the lexan spoiler. If so you are likely used to seeing me in a Mazda 3 and RV instead of the Porsche.

 

If you need the Electrical Manual but can't find it on-line, let me know. I have the hard-copy.
Nope...not me. Mine's red (see photo album in my profile). I haven't autox'd for a few years but use to make some of the events. I sucked in ASP. Hoping to get some lessons and a set of 'R' compounds someday soon and get back into it.

 

Another thing to think about is how much cheaper/easier it is to replace an apex seal rather than finding and buying a good clean housing.

 

Not to mention combining that with turbo applications. On top of all that stress then getting air forced into there with a decent amount of pressure stock, then usually the boost pressure is raised for tune/power reasons at some stage in their life. That's a lot of stress, also pushing along carbon build up in most cases. It's amazing they don't break more often in my opinion, I'm glad they don't :P