Why Apex Seals Fail

[Barry Bordes]

So you can try a little experiment to test this hypothesis. Install a .0015” feeler gauge at the center of the apex seal simulating the raised spark plug area. The seal will be rocked-over .003“ and the wedge will put pressure on the pointed end of the apex seal. Note the exaggerated condition depicted at the top of the picture.



But we still haven’t gotten to the root cause. The real problem is the raised spark plug area on the housing. There are at least three approaches to this problem:

(1)- Use cold heat range plugs like NGK R7420-10 or 10.5. (This is easiest part of the solution.)

(2)-The harder second part is to cool the housing better.
A better pump is a good start. Second gen. cast impeller type pumps are a lot better or the Remedy pump for 3rd gens.

(3)-The most difficult part would be to port the housing in the spark plug area to minimize distortion.

But what is the best way?
The factory racing peripheral housing have a trough cast into the inner water jacket in this area but the are for NA applications.


Notice that the thru-bolt bosses have been severed.

[GoopyPerformance]

Originally Posted by Barry Bordes

But we still haven’t gotten to the root cause. The real problem is the raised spark plug area on the housing. There are at least three approaches to this problem:
.

Our surface re-refreshing has virtually eliminated the spark plug hole raising issue. In fact this high spot is more detrimental than housing edge damage.
The cracks in the OEM Apex Seals are due to their hardness.

I noticed 20-30 compression gains on rotor housings when re-freshed using our Apex Seals and these are housings that would otherwise go to the trash.

A few years ago we posted a 135PSI 12A engine that we built but no one
believed now Judge ito has been building 130 to 140PSI Engines daily with used (refreshed) rotor housings but one thing is for sure the raised spark plug area is a problem if not addressed.
http://rotarycarclub.com/rotary_foru...t=12967&page=5

[Barry Bordes]

Originally Posted by GoopyPerformance

Our surface re-refreshing has virtually eliminated the spark plug hole raising issue. In fact this high spot is more detrimental than housing edge damage.
The cracks in the OEM Apex Seals are due to their hardness.

I noticed 20-30 compression gains on rotor housings when re-freshed using our Apex Seals and these are housings that would otherwise go to the trash.

A few years ago we posted a 135PSI 12A engine that we built but no one
believed now Judge ito has been building 130 to 140PSI Engines daily with used (refreshed) rotor housings but one thing is for sure the raised spark plug area is a problem if not addressed.
http://rotarycarclub.com/rotary_foru...t=12967&page=5

Jonathan, have you thought about heating the plug area while grinding the housing surface?
I believe the factory started grinding either the apex seals or the housing surface that way for better fit while running.
Barry

[j9fd3s]

Originally Posted by Barry Bordes

Jonathan, have you thought about heating the plug area while grinding the housing surface?
I believe the factory started grinding either the apex seals or the housing surface that way for better fit while running.
Barry

i'm not sure where this is mentioned, but a new factory apex seal isn't flat, its bowed slightly, so that when its in a working engine and up to temp its flat.

another problem on used housings, this is why they shrink, and why we measure for width, is that the steel liner actually collapses in the compression area, so the center of the housing bows in. its very bad to have leakage between chambers...


mike

[Barry Bordes]

Originally Posted by j9fd3s

i'm not sure where this is mentioned, but a new factory apex seal isn't flat, its bowed slightly, so that when its in a working engine and up to temp its flat.

another problem on used housings, this is why they shrink, and why we measure for width, is that the steel liner actually collapses in the compression area, so the center of the housing bows in. its very bad to have leakage between chambers...
mike

Mike, a slightly different interpretation of the housing wear could be that the high temps in the spark plug area cause expansion between the torqued plates which in turn compresses the surface, distorts the face, and chafes the faying surfaces (which causes the undersize housing measurements).

Notice the temps where we want to provide extra cooling are doubled that of atmospheric boiling water.
Barry

[j9fd3s]

that very well could be. next time you have some used housings handy, take a straight edge and lay it across the surface, its above the spark plugs that seems to do the worst.

i did build a couple of motors with a stock diameter stud kit, and i was told to tighten it to 50lbs, but i think this is actually bad. it also certainly didn't solve the actual problem which was stock ecu/injectors with a street port and big turbo! or more correctly the owner.

after thinking about it, i think the small diameter studs actually hurt more than they help. the studs DO NOT locate any of the housings any better than the stock bolts, plus #50lbs of torque the rotor housings probably ARE bowing, which is bad!

mike