Today's Message Index:
----------------------
1. 06:37 AM - Re: Knock sensors (Gary Casey)
2. 09:38 AM - (Fwd) Re: Knock sensors? (Jim Baker)
3. 05:42 PM - Re: Re: Knock sensors (AzevedoFlyer@aol.com)
4. 08:26 PM - Re: Knock sensors? (Fiveonepw@aol.com)
5. 09:56 PM - Re: Knock sensors? (David M.)
Message 1
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| Subject: | Re: Knock sensors |
Very interesting. Does it measure pressure or flow? At my day job
we build both for large engines, typically multi-thousand hp mining
truck engines. The flow is still measured by pressure - pressure
drop in a venturi. I agree, one nice thing about measuring crankcase
pressure is that it is totally non-invasive and doesn't affect the
base engine operation at all. Having such a thing would have stopped
me from taking off when a ring broke on my IO-360. Turns out I was
stopped by someone driving up and blocking my way, telling me I was
blowing smoke (come to think of it, I've had people tell me that a
number of times..:-).
Gary Casey
>
> Time: 06:51:36 PM PST US
> From: AzevedoFlyer@aol.com
> Subject: Re: Engines-List: Knock sensors
>
> Dean and All,
> No question that an electronic means of knock detection is the
> preferred
> route, given its sensitivity and ease of integration to the
> electronic ECU. For
>
> altogether different reasons, I developed (...and have a Form 337
> granted by
> FAA) what I call an Engine Health Monitor Indicator (EHMI) and have
> it in my
> instrument panel.
> The EHMI monitors
> (passively) the blowby emitted. On a modified meter, there are
> bands colored
> Green / Yellow and Red. During take off you have the worst
> condition in which
>
(snip)
> Miguel
> PA22/20-150
> N8714D
Message 2
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| Subject: | Re: Knock sensors? |
X-mailer: Pegasus Mail for Windows (4.41)
> I read years ago that knock sensors were tried but didn't work because
> with the piston slap that is present in air cooled aircraft engines
> makes it difficult for the sensor to determine the difference between
> piston slap and 'knock.'
Can't speak to the whole issue but...
I live a short ways from GAMI at Ada, OK. While over there one day I asked
about their electronic ignition. They're using an optical sensor (laser pulsed
into the cylinder via a fiber optic cable situated on an offset spark plug). The
regular 18 mm plug has the cylinder offset axially from the center and the
fiber optic is positioned on the other side. The laser detects the onset of
detonation through some sophisticated algorithims looking at charge density
and flame front propagation (as they explained it to me). GAMI chose the
nastiest engine known in terms of detonation sensitivity, a TSIO 540. They
can virtually feed this beast almost anything combustible and it runs without
complaint. They even demonstarte changing fuel types during a full power
test cell run and you'd never know anything had changed except by watching
the timing and EGT changes on the data screen. Its been a year or so since I
saw it in operation and don't know their current status for certification testing.
Jim Baker
580.788.2779
'71 SV, 492TC
Elmore City, OK
Message 3
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| Subject: | Re: Knock sensors |
Gary,
It translates pressure measured through a modified Pitot Tube into flow.
Thanks,
Miguel
Message 4
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| Subject: | Re: Knock sensors? |
In a message dated 10/12/2007 8:27:32 PM Central Daylight Time,
azevedoflyer@aol.com writes:
Aircooled engines complicate things a bit because of the finning which
radiate vibration in a very ample spectrum.
>>>
Based on my meager understanding of knock sensor physics in automotive
applications, this was my primary suspicion- how to isolate specific "knock"
signatures when you have several hundred fins vibrating in multiple frequencies
and
harmonics of same. If Lycosaurs were falling from the sky due to detonation at
the hands of efficiency-desparate pilots, I'd believe market and/or
regulatory pressure would force development of such a system. Perhaps when domestic
airplane fuel hits European price$ and truly efficient operation becomes a
defining market factor, this technology will develop and we'll have a new paradigm:
LOD operation vs. LOP, just like in your average run-of-the-mill ten-year-old
Nissan Sentra....
With the astonishing capacity of modern digital processing, I can't
understand how an on-board processor couldn't sample vibratation sendor data from
multiple points, compare that against know "safe" data, then somehow annunciate
a
potentially unsafe condition and/or make appropriate adjustments to whatever
engine-management scenario a pilot may employ in the ultimate interest of
maximizing efficiency.
Here's hoping that if observers from the Lycoming/Continental intelligentsia
have comments, they'd chime in here, even if covertly.
Appreciate the discussion-
Mark
Message 5
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| Subject: | Re: Knock sensors? |
if efficiency were truly a concern, they'd all convert to fuel
injection. If that, then the pilot would have no control over anything
except which way to point -- and would not need it. The computer would
control LOP etc.
David M.
----- Original Message -----
From: Fiveonepw@aol.com
To: engines-list@matronics.com
Sent: Sunday, October 14, 2007 10:14 PM
Subject: Re: Engines-List: Knock sensors?
In a message dated 10/12/2007 8:27:32 PM Central Daylight Time,
azevedoflyer@aol.com writes:
Aircooled engines complicate things a bit because of the finning
which radiate vibration in a very ample spectrum.
>>>
Based on my meager understanding of knock sensor physics in automotive
applications, this was my primary suspicion- how to isolate specific
"knock" signatures when you have several hundred fins vibrating in
multiple frequencies and harmonics of same. If Lycosaurs were falling
from the sky due to detonation at the hands of efficiency-desparate
pilots, I'd believe market and/or regulatory pressure would force
development of such a system. Perhaps when domestic airplane fuel hits
European price$ and truly efficient operation becomes a defining market
factor, this technology will develop and we'll have a new paradigm: LOD
operation vs. LOP, just like in your average run-of-the-mill
ten-year-old Nissan Sentra....
With the astonishing capacity of modern digital processing, I can't
understand how an on-board processor couldn't sample vibratation sendor
data from multiple points, compare that against know "safe" data, then
somehow annunciate a potentially unsafe condition and/or make
appropriate adjustments to whatever engine-management scenario a pilot
may employ in the ultimate interest of maximizing efficiency.
Here's hoping that if observers from the Lycoming/Continental
intelligentsia have comments, they'd chime in here, even if covertly.
Appreciate the discussion-
Mark
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