I found an old SAE paper 730119 on the OMC engine.
A very interesting paper.
I noticed that OMC had good luck with aluminum
side housings made from hypereutectic aluminum.
The same process used by GM on the Vega engine.
Does anybody have any direct experience with
OMC snow mobile rotary engine side housing wear problems?

I wonder how Silicon Nitride ceramic
side seals would work on hypereutectic aluminum.

Perhaps OMC was better able to control the casting
process than GM.


Paul Lamar ...No rotor no motor.

Paul,
I mentioned this before, and perhaps you heard differently through your
Chapparal contacts, but I was told the engine blocks on the Vega engine
worked fine by people in the know. Many other problems including valve
guides which caused most of the smokers rather than the block.The
Porsche 928 V8 and many of the current MB V8's use the same technology.
I thought this might be a good possibility, but I doubt that Mazda would
have missed it if that had been the case.
Bill Jepson

BMW had problems with the sulfur content in US gasoline eating up the
bore in their aluminum blocks on the 3L V8 (530i cars) - 10 years ago.
I haven't heard of more recent issues.

Other question..  It's my impression that the apex seals take more
abuse than the side seals, and similarly the rotor housing wear
surface needs to be tougher than the side housing wear surface.  Is
this correct?  Does that allow using a coating that's less tough on
the side housing?  It's apples to oranges, right?



Regards,

Matt-

I would say yes Matt. Just an impression I get. However the side housings
wear more than the rotor housings. Once the ridges are over a couple of
thou the housings need lapping or replacing. I suspect the cast iron side
housings could benefit from the same chrome treatment given to the
rotor housings.

The wear on the rotor housings are well within acceptable limits as long
as the apex seals remain intact. With the Mazda system of chrome over
steel.... cast iron apex seal wear is projected to be about 3,000 hours.
With Silicon Nitride ceramic apex seals wear is projected to be 30,000 hours.
Of course no one has worn out a ceramic apex seal yet.
-- 
Paul Lamar ...No rotor no motor.

Paul,

Ethanol fuels will dissolve unprotected aluminum.

Doug

Looks like it is out for Porsche's, BMW's and Mercedes.
Not to mention all the other companies that are planning to
switch to un lined aluminum cylinder bores.

Paul Lamar ...No rotor no motor.

Paul

Anodized aluminum works.

Doug

I don't think so. That is a very thin coating.
I also don't think anodizing works on silcon. I could be wrong.

Paul Lamar ...No rotor no motor.

When I was at Federal Mogul, in testing anodizing showed it was simply a
corrosion and cosmetics coatings, NOT a durability layer.

-dave

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