A detonation event at wide open throttle will usually break
out the dowel hole in the rear iron. This was a big problem in the FC models and
Mazda added material around the dowel hole in the FD twin turbo engines.
Detonation will continue until some parameter changes, like a seal shears off
and compression is lost. Throttle setting is reduced, or, the knock sensor
causes the timing to be pulled out smartly.
A crossfire where a rear housing plug wire excites a front plug
wire or front ignition primary or trigger wire will break out the front iron
dowel hole. That is a 180 degree too soon ignition advance. A lump of FOD can do
in either dowel hole.
Detonation is charge temperature dependant. It is uncommon in NA
engines. It is common in boosted engines. Notice that Racing Beat recommends
testing boosted engines at not more than 10 degrees of total advance, and racing
on not more than 12 degrees. As boost pressure goes up so does effective
compression ratio. So, the burn rate (Flame front velocity) goes up and the
amount of advance required to maximum cylinder pressure at 50 degrees ATDC goes
down.
Intercoolers are used to reduce charge temperatures. Over cooling
the oil to reduce rotor face temperatures is a help. Coolant temps not over 180
degrees helps. Water spray on the intercoolers, water and oil coolers helps. Run
over rich during high throttle settings to fuel cool the mixture helps. Over
rich premix includes extra top oil as well. Using high octane
fuel.
Using ICE COLD heat range plugs helps.
Piston engines can survive a FOD event (you find a 10-24 nut
pressed into a piston top 2 years later) a rotary will not survive a FOD event
of any but microscopic size.
Run an air filter for all powered operations.
On another note:
I saw the Dayton airshow crash along with my daughter and her male
friend. I am jaded to this type of disaster, but my daughter and her friend were
not. It seems as though several thousands of
guests were not ready to suffer this calamity. I called out to my
daughter when I saw the problem hoping she would turn to me and not see the
outcome. But I was too late.
In my opinion: The turn into the show line was from too low an
altitude. It was very hot about 86 degrees. The turn was to down wind. The roll
to inverted was crisp and slowed the plane further.
The pilot pushed forward stick (late) to raise the nose, then I
suspect he attempted to roll upright when he felt a stall start, after only a
second of inverted and I saw him pull up elevator while partially inverted. The
down wing struck the ground. Another 25 feet and he might have pulled it off.
There was very little fuel on board, but enough to make a large fire ball. The
engine sounded
like it was making full power all the way to the ground. Last night
was the first time I did not dream of it. The show went on again Sunday but
attendance was even worse than Saturday. No military stuff at all. Thank you
Obama.
Lynn E. Hanover
I broke an iron once … the engine slipped during
hoisting and broke the casting of one outside tension bolt carrier … not
thermal shock.
Jeff
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From:
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Subject:
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Re:
[FlyRotary] Re: Blown engine
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Date:
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Mon,
24 Jun 2013 11:00:53 -0600
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To:
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FWIW,
the thermal shock story is totally bogus.
Tracy
Sent
from my iPad
Scott,
I have never
heard of an iron breaking from thermal shock. I routinely mistreat
mine in that manner.
Don't forget
to take everything Dave Atkins says with a grain of salt. He has
not always been the most straight forward of salesmen.
I showed the
damaged rotor, rotor housing and front side iron to Dave Atkins, the
local expert. He thinks my engine suffered FOD but the entry point is a
mystery. The broken side iron is My fault: thermal shock. The aluminum
rotor housing experienced thermal expansion faster and greater than the
side iron because I went to high power before the engine was
sufficiently warm. The alignment dowel was moved outward by the growing
aluminum housing and cracked out the side iron around the dowel, which
is also the oil gallery
Sent from my
iPhone
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