Today's Message Index:
----------------------
1. 06:05 AM - Re: Engines-List Digest: 5 Msgs - 10/10/07 (Gary Casey)
2. 11:57 AM - Re: Ring Flutter? (teamgrumman@aol.com)
3. 08:11 PM - Knock sensors? (Fiveonepw@aol.com)
Message 1
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| Subject: | Re: Engines-List Digest: 5 Msgs - 10/10/07 |
I'm not a certified engine expert (although I am probably certifiable
in other catagories...:-), but in my experience "ring flutter" is
something the engine builder will use to explain broken rings found
after a teardown. The owner will then nod and pay the bill.
Presumably the the ring starts to vibrate away from the cylinder wall
in waves. Some will say it can happen at very high piston speeds or
with a cylinder that is badly worn - or if the cylinder pressure is
rapidly changing as in a detonation event. Regardless, it is the
result of something bad, not the cause of it. How someone can
diagnose "ring flutter" without having torn down the engine I don't
know. I certainly wouldn't lose any sleep over it, but at the same
time keeping the timing correct will maintain a margin against
detonation. Most naturally-aspirated aircraft engines have a robust
margin anyway, except when overheating while running on one mag.
Gary Casey
>
> Time: 04:38:19 AM PST US
> From: Fredrick Kerfoot <fredkt46@hotmail.com>
> Subject: Engines-List: Ring Flutter?
>
>
> What is piston "Ring Flutter"?? I have an IO360. Just how
> concerned shoul
> d I be?
>
> Fred K
Message 2
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| Subject: | Re: Ring Flutter? |
Finally, someone who paying attention.
Ring flutter is very rare. Especially at less than 2700 rpm. Piston
ring seal depends on a balance of four forces: combustion pressure,
ring inertia, the rings radial expansion pressure and crankcase
pressure. Ring flutter is uncontrolled oscillation due to an imbalance
of those forces. Once a pistons rings go into flutter, their ability
to scrape oil off the cylinder wall as the piston moves downward is
impaired, blow-by increases and oil consumption rises dramatically.
The combination of high rpm and low crankcase pressure typical of low
engine loads causes those four forces to become imbalanced. The small
amount time the engine sees regular, high-rpm, light-load operation, is
rare. Even so, if that happens, you may experience ring flutter and
high oil consumption, but not likely.
-----Original Message-----
From: Kelly McMullen <apilot2@gmail.com>
Sent: Wed, 10 Oct 2007 6:43 pm
Subject: Re: Engines-List: Ring Flutter?
I guess I just don't see how you relate a question about theoretical
ring flutter with engine timing or age of fuel. I'm missing the
connection. Actually a 180 only requires 91-96 or 91 mogas with STC.
Only the 160 and the 200hp versions need the extra octane.
On 10/10/07, Gene Smith <esmith6@satx.rr.com> wrote:
I would be concerned...I suggest you check your engine
timing...Also if your fuel is old, it has lost some of it's volatility,
and I
would drain it and replace it with "fresh" gasoline...Are you burning
Auto
Gas?..The book says that 360 needs 100LL (all of them, 160 and above
require
it.)....................Good
Luck.......................CHEERS!!!!.............................Gene
Smith.
----- Original Message -----
From:
Fredrick
Kerfoot
To:
engines-list@matronics.com
Sent: Wednesday, October 10, 2007 6:37
AM
Subject: Engines-List: Ring
Flutter?
What is piston "Ring Flutter"?? I have an
IO360. Just how concerned should I be?
Fred K
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Message 3
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We've had knock sensors on cars for many years that retard timing in the
event of detonation to keep engines running at peak fuel efficiency. Since it
is
almost impossible to detect thru conventional aircraft engine instrumentation
that I'm aware of, or audibly, (such as in cars) that such a device would be
very useful in planes, but I've never heard of such a critter. I'm kinda
guessing that it is difficult in an air-cooled engine or because of the large
cylinder displacement.
Anyone aware of any attempts to do this on Lycs or Conts?
Mark Phillips
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