Is this rotor usable?

[RETed]

Originally Posted by JustJeff

I'm a lil confused by the context of this statement. You saying OEM or better apex are good for 400hp. Or that OEM or better in relation to my damaged rotor?

Oh boy, this is going to open a big can of worms...

I've always advocated the use of Mazda OEM apex seals for anything under 500hp.
They are proven, and other, superior options like "ceramics" are significantly more costly.
I've done a lot of motors with the Mazda OEM apex seals, so I know what they can and cannot do.

Several years ago, they was a proliferation of aftermarket apex seals all touting all kinds of benefits.
Remember Hurley Engineering? Crap. Seals tend to obliterate when pushed moderately. Some people claim these seals did not score housings when they let go, so this was a plus??? *ROLL EYES* You still need to rebuild the motors when seals let go.
Rotary Aviation? I dunno what generation they were on, but the early versions all had problems. Some were too soft. Some were too hard. I've had customer cars who had badly eaten rotor housings prematurely cause of RA seals that were too hard.
(I only kept track of these aftermarket apex seals until about 5 years ago, so some of this info might be outdated.)
It looks like the RA is a little better, but previous experience has left a bad taste in my mouth.
Atkins? Relatively new, but consensus was that you could not use them over 15psi. WTF? I don't like have boost limitations on my motors like that. The relatively low boost level implies these seals are on the softer side.

What I do know as fact...
We sent the Mazda OEM apex seals out for hardness testing, and results were...interesting.
Mazda has long said that their apex seals are electron beam hardened on the leading edge (the edge that contacts the rotor housing).
We found this out to be true.
The leading edge measure to approximately 60C Brinnell hardness.
The "back" side of the apex seal measure to approximately 40C Brinnell hardness.
This expensive treatment of the apex seals were not being done to most of the aftermarket apex seals out there - most aftermarket apex seals were of homogeneous hardness throughout the entire seal.
What does this expensive treatment by Mazda accomplish?
Two things...
1) The leading edge which is exposed to the most abuse (contact with rotor housing and exposure to combustion gases) is more resistant to wear & tear.
2) The back side of the apex seal that sits in the rotor is softer so it doesn't pound the apex seal springs and the rotor groove.
Yes, some of the harder aftermarket apex seals were causing excessive clearances in the rotor apex seal groove over time.
Excessive clearances will cause excessive combustion gas blow-by and, in extreme cases, contact of the rotor apex tips with the rotor housings.

I've had this information posted on my web site for years now:
http://fc3spro.com/TECH/MODS/ENGINE/...OTORS/apex.htm

I don't have any experience with any of the more expensive options like NRS, Ianetti, or any of those "cermamics".
All of these options are significantly most costly than the Mazda OEM apex seals at around $500 for a set of 6.

Back to the original question...
I set my standard for apex seals with the Mazda OEM units.
Most of the affordable aftermarket apex seals I don't consider equivalent to the Mazda OEM stuff.
Most of the more expensive stuff (which I have zero experience with) is probably better than the Mazda OEM units due to their sheer price tag.


-Ted