-"Brian D. Cain" wrote:

Hey George,

I'm still not totally sold on the idea of 3mm although I did use them

for

some time
on an engine that I ran on one of my setups for a few years.  I've been
going back
and forth with it and the only conclusion I can come up with is that

they're

used
and/or recommended because they're a bandaid.  That's the only thing I

can

truthfully conclude about that.  From some people I've spoken to on it

(that

are
decidedly anti-3mm), they've said that there's increased wear on the

rotor

housings
near the leading/trailing spark plug holes from chatter, there's less
sealing and more
blow-by at lower RPM's, and there's something else also concerning

shearing

and
loads put against the seal but I don't know.  It's an area of science

I'm

unfamiliar
with; perhaps some of you more enlightened guys can shed some light on

that.

The other issue I've been curious about is the use of 2-piece 2mm vs.
3-piece 2mm
apex seals with respect to their resilience to severe engine knock.
Regardless of
the alloy or heat treatment used on the seal for strength purposes, is

it

possible that
a 2-piece seal, where both of the "long" portions of the apex seal are

one

piece, is
structurally stronger as opposed to its 3-piece counterpart?  Every

engine

that I've
seen personally let go from engine knock has always used the factory,

Mazda

3-piece design.  It seems to me that a thicker chunk of anything would
withstand
more impact or force than something that was the same mass yet split

into

two pieces.
Anybody have anything they could add to that?

B

Brian,
 I think your probably right about the 3mm, as some of these things have
been mentioned before, however for outright strength the 3mm 2 piece choice
seems to be the choice for a hard working rotary.

The 12A goes well with a 3mm and I think the RX8 has 3mm.
What I want to know about is the 3mm 1 piece and how good that is - any info
?
Is it a filed fit !?

Also you mention (in your last post) on spark plug timing. There would seem
to be some consensus (on ACRE) that for our application that the firing of
the plugs at the same time has no adverse effect - what's your take on this.
George (down under)

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