This is an interesting  picture from the Mazdatrix web site.

This must happen around  four hundred HP per
rotor on turbo engines :-) I suspect it is caused by detonation
at that power level as it is in the right place on the
rotor flank where detonation occurs. Lower compression ratio
anyone? :-) It could also be caused by inadequate rotor cooling
at that power level.

Paul Lamar

I saw this a few months back on a website, I'm still wondering how much
boost they were running to collapse the face.  I believe they were also
having problems with rotor housing distortion as well.

--
Chris
microcosman.com

It could also be a casting flaw or core shift as this is a common
occurance.

Paul Lamar
 
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