Why Apex Seals Fail

[Barry Bordes]

Originally Posted by GoopyPerformance

This is a very interesting post but the title "why apex seals break" may be misleading.

Lets be careful and not add to much theory and 1000 dollar words and confuse some of the laymen who are just coming to the rotary scene.

We all know that the web is full of data but gotten to the point that true information is lost or siphoning out the good stuff becomes almost imposable, with that in mind lets keep this forum
nonsense free.

Now the specifics on why this post can be misleading is because the breakage on the end of the long part (hypotenuse) only happens on OEM 93-94 2 peace seals.

Most rotary engines are built with OEM 2 piece seals.

Also the end tip on the OEM seals gets within a few thou of the irons of either side, where the sharp tip may catch the iron when the engine detonates and rotor tip hits the irons. We see this often with drag cars pushing 40+ lbs of boost. Cutting the rotor faces
alleviates some of these issues.

I have not seen the sharp ends scrap the side housings.

That margin on the triangle protecting the tip looks like about .020" on the 2 piece and .040" on the three piece OEM seals.
See attached below.


(Aftermarket seals including ours have a larger Side peace than OEM.)

This also happened on engines with fresh new housings and new OEM Apex seals.
Therefore if the apex seal cracked (hypotenuse) it happened when the engine leaned out or detonated, these are drag cars which never get any road millage where the (hypotenuse) area can slowly crack then one day let go completely.

Even if the hypotenuse area of the apex seal was further inward or even if you used a 1 piece apex seal, leaning fuel, TOO much advanced ignition or detonation are still why apex seals break.

We have been working on Apex Seal technology for almost 10 years with collaboration from engine builders both stateside and Puerto Rico and agree this breakage (hypotenuse) end tip break off is primarily a oem seal issue.

Glory to GOD!

I think we are addressing two different groups. I am trying to help the regular guy that wants to make a long-term dependable engine (usually with OEM parts).
You are working with racers that are pushing the envelope.

Although I test often for detonation with my TFX in-chamber sensor rig I have not experienced any detonation yet. Thank Goodness!

When your seals do fail where is the damage normally located?

Good luck with your Goopy seals and housings.
Barry