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Message
What I seem to have missed is the compelling reason
why we
can't simply mill the slots out to 3 mm, install new seals and
continue the
march. I know Tracy's "new formulation" seals only come in
2 mm, but I
speculate that would be pretty easy to change given the
current rash of
wallowed out 2 mm slots and the potential market for
3mm
versions.
Hi
Jim,
First, Tracy's/Bruce's
new seals are certainly available in 3mm, and at the same price of the 2mm
seals. From what I've understood (or thought I did), the 2mm
seals actually "seal" better than the 3mm seals. For a street engine,
(idle, emissions, etc) that's clearly better, or Mazda wouldn't have changed to
them in 86 (I think). I don't think there's anything really wrong with
running 3mm seals if you want to.
I'm more interested in
what causes the slots to open up. If Bruce is correct, and
they're just bent outward, then I guess the force of combustion is causing
this??? Imagine when the plug fires, there's a huge force
created. That force would push outward on the two apex seals that border
that particular rotor face. When the next face fires, the seal that was
previously forced backwards, is now forced forward. I can imagine that
this back and forth hammering would tend to open up the slot. I
guess the real question is what causes this to be worse in some engines than
others. The obvious answer would be that it's worse in engines that
produce lots of power, for long periods of time.
Lynn, Leon, do you see this in racing
engines?
If all the above is
true, then I can also see far more stress being put on the seals as the slot
widens. Imagine the seals slapping back and forth rapidly. What
happens if a tiny bit of carbon, sand, etc manages to get in the
apex slot, and then the seal is slammed into it. Wouldn't
that offer the opportunity to snap a brittle
seal?
To add to this SWAGing,
I would also like to mention that Ed is not alone with his observation of
excessive wear on Hurley seals. My engine probably had 80 total hours on
it before the oil cooler incident, and there's a remarkable amount of wear
on the sides of my seals. These were in new rotors, and the apex
slots are still at new specs, so it wasn't caused by out of spec slots.
Leon may have a point about dust in this case, since I didn't run with a
filter, and half of my running time was on the
ground.
At some point,
I'm going to measure one of the old Hurley seals to see just how much of
a groove was worn in them. Just from looking at them, I can tell
that it's much more wear than the Mazda seals in the old (??? miles) engine
in the box in the garage. Suffice to say that I'm happy that I
have the new seals in my current engine.
Cheers,
Rusty (firewire hard
drives biting the dust left and right...)
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