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Engine Cowl Temperatures

 
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George W Braly



Joined: 09 Jan 2006
Posts: 15

PostPosted: Sat Feb 04, 2006 2:27 pm    Post subject: Engine Cowl Temperatures Reply with quote

Bob,

I installed some thermocouples in the engine compartment of a turbo
Bonanza in a variety of places.

OAT 107dF. Wind nil. Took off and flew around at high power with the
gear down until I had the cylinders up to the 420dF range.

Did an immediate landing. Taxi about 125 yards and put the airplane into
a closed T-hangar.

I then monitored the temps for the next 45 minutes.

At about 25 to 30 minutes the temps all reached peak from heat soak from
the engine core.

The surface temperature of the magneto case was the hottest temperature
I measured. It was around 222d F. I assume the core was a bit hotter.

The rest of the temps, including the local ambient inside the cowling
were lower.

Regards, George


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brian



Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

PostPosted: Sat Feb 04, 2006 3:55 pm    Post subject: Engine Cowl Temperatures Reply with quote

George Braly wrote:

Quote:
I installed some thermocouples in the engine compartment of a turbo
Bonanza in a variety of places.
...
The surface temperature of the magneto case was the hottest temperature
I measured. It was around 222d F. I assume the core was a bit hotter.

The rest of the temps, including the local ambient inside the cowling
were lower.

It is nice to see people who actively seek truth.

--
Brian Lloyd 361 Catterline Way
brian-yak at lloyd dot com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery


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brian-yak at lloyd dot com
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I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery
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alexpeterson(at)earthlink
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PostPosted: Sat Feb 04, 2006 4:55 pm    Post subject: Engine Cowl Temperatures Reply with quote

Quote:
George Braly wrote:

> I installed some thermocouples in the engine compartment of
a turbo
>Bonanza in a variety of places.
>...
> The surface temperature of the magneto case was the hottest
>temperature I measured. It was around 222d F. I assume
the core was a bit hotter.
>
> The rest of the temps, including the local ambient inside
the cowling
> were lower.

It is nice to see people who actively seek truth.

--
Brian Lloyd 361 Catterline Way

I agree completely about seeking facts, thanks George.

Somewhat related, I always open my oil door when I shut down, unless it is
10F outside like today, and I'm conserving heat for a few hours.
Additionally, when shutting down for the day, I pull the dipstick up until
it can move slightly to the side. It is amazing how much steam comes up out
of there. Where do you suppose that steam would end up if you leave the
dipstick in tight?

Alex Peterson
RV6-A N66AP 712 hours
Maple Grove, MN


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nuckollsr(at)cox.net
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PostPosted: Sat Feb 04, 2006 5:32 pm    Post subject: Engine Cowl Temperatures Reply with quote

At 07:03 AM 2/4/2006 -0600, you wrote:

Quote:

Bob,

I installed some thermocouples in the engine compartment of a turbo
Bonanza in a variety of places.

OAT 107dF. Wind nil. Took off and flew around at high power with the
gear down until I had the cylinders up to the 420dF range.

Did an immediate landing. Taxi about 125 yards and put the airplane into
a closed T-hangar.

I then monitored the temps for the next 45 minutes.

At about 25 to 30 minutes the temps all reached peak from heat soak from
the engine core.

The surface temperature of the magneto case was the hottest temperature
I measured. It was around 222d F. I assume the core was a bit hotter.

The rest of the temps, including the local ambient inside the cowling
were lower.

That jives with my recollection of some studies another
engineer at Electromech did about 25 years ago . . on our
company owned A36. I wasn't directly involved with the work
and had no reason to do a gray-matter stash of the data.

I'm sure we've done a boat-load of temperature surveys on
Bonanzas at RAC. I'll dig around in the reports file and see
what I can find.

Bob . . .


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bakerocb



Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

PostPosted: Sun Feb 05, 2006 8:03 am    Post subject: Engine Cowl Temperatures Reply with quote

Responding to an AeroElectric-List message previously posted by: "Alex
Peterson" <alexpeterson(at)earthlink.net>

<<.....skip......Somewhat related, I always open my oil door when I shut
down, unless it is
10F outside like today, and I'm conserving heat for a few hours.
Additionally, when shutting down for the day, I pull the dipstick up until
it can move slightly to the side. It is amazing how much steam comes up out
of there. Where do you suppose that steam would end up if you leave the
dipstick in tight? Alex Peterson>>

2/5/2006

Hello Alex, Thanks for your input. I am now going to start opening my
dipstick cap also.

How much of that "steam" do you suppose is oil vapor instead of water vapor?
I plan to let some of it condense on a cold mirror or glass to see how
greasy it is.

OC


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George W Braly



Joined: 09 Jan 2006
Posts: 15

PostPosted: Sun Feb 05, 2006 8:42 am    Post subject: Engine Cowl Temperatures Reply with quote

Keep in mind that if you get the oil hot enough on each flight to boil
off the water in the oil - - then opening the dip stick filler tube
appears to accomplish very little.

I like to see the oil temp get to at least 180-190dF above 5000 feet on
each flight to make sure the water turns to vapor and out the breather
tube.

I think a lot of these nifty little "tricks" - - that have accumulated
over the years really turn out to be based on very little data. In many
cases there appears to not really even be a theoretical basis as to why
the practice is better. (Turbo cool down 5 minute waits, is another
example.)

Regards, George

--


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welchvincent(at)hotmail.c
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PostPosted: Sun Feb 05, 2006 9:13 am    Post subject: Engine Cowl Temperatures Reply with quote

Just a quick question Alex. As the engine cools with the dipstick open,
won't that just suck more (possibly moisture laden) air back into the oil
sump?
Vince
Quote:
From: <bakerocb(at)cox.net>
Reply-To: aeroelectric-list(at)matronics.com
To: <aeroelectric-list(at)matronics.com>, <alexpeterson(at)earthlink.net>
Subject: Engine Cowl Temperatures
Date: Sun, 5 Feb 2006 11:00:36 -0500


Responding to an AeroElectric-List message previously posted by: "Alex
Peterson" <alexpeterson(at)earthlink.net>

<<.....skip......Somewhat related, I always open my oil door when I shut
down, unless it is
10F outside like today, and I'm conserving heat for a few hours.
Additionally, when shutting down for the day, I pull the dipstick up until
it can move slightly to the side. It is amazing how much steam comes up
out
of there. Where do you suppose that steam would end up if you leave the
dipstick in tight? Alex Peterson>>

2/5/2006

Hello Alex, Thanks for your input. I am now going to start opening my
dipstick cap also.

How much of that "steam" do you suppose is oil vapor instead of water
vapor?
I plan to let some of it condense on a cold mirror or glass to see how
greasy it is.

OC





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aadamson(at)highrf.com
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PostPosted: Sun Feb 05, 2006 10:02 am    Post subject: Engine Cowl Temperatures Reply with quote

Yep, I would agree, if the Oil temp is above in the operating range, and
based upon Georges data, that the temp outside after shutdown was close to
the boiling stage, then all the water should have be evaporated. Opening
the dip stick cause me two concerns. It allows FOD (bugs come to mind) and
condensated moisture a place to get into the engine. That little dip stick
makes for a good conduit for both.

Oil won't COKE until it's way hotter than our operating temps and with
today's oils, I suspect that the "blend" compensates for any tendency to
COKE anyway.

Alan

--


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skywagon(at)charter.net
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PostPosted: Sun Feb 05, 2006 10:05 am    Post subject: Engine Cowl Temperatures Reply with quote

George nailed it.....
99% of internal case moisture is blasted out the breather as all the
internal thrashing is going on at elevated temps. I suspect the moisture
vapor seen at the dipstick opening is very minor and is probably what was
trapped in the tube itself.

I do like to opening the top cowl door, oil fill in my case, as that lets
latent heat escape faster and may, in the long run, be easier on all the
non-metal stuff that is associated with the top of an engine. However, if
your top cowl door is pretty high, out of eye sight, it maybe easy to forget
to close it for the next quickie flight. I took a block of soft foam, cut a
slit in it, and slide the edge of the door into the slit. This way the door
stands straight up in easy eye sight as well as the foam has to be removed,
etc. Never forgotten to close it this way.....
D

---


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alexpeterson(at)earthlink
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PostPosted: Sun Feb 05, 2006 3:15 pm    Post subject: Engine Cowl Temperatures Reply with quote

Quote:

--> <welchvincent(at)hotmail.com>

Just a quick question Alex. As the engine cools with the
dipstick open, won't that just suck more (possibly moisture
laden) air back into the oil sump?


Vince

Vince, this would happen without opening the oil stick, as it would simply
go into the breather in any case. I'm sure the dewpoint inside an engine
upon shutdown is higher than FL in the summer.

Alex Peterson
RV6-A N66AP 712 hours
Maple Grove, MN


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PostPosted: Sun Feb 05, 2006 3:15 pm    Post subject: Engine Cowl Temperatures Reply with quote

Quote:
2/5/2006

Hello Alex, Thanks for your input. I am now going to start
opening my dipstick cap also.

How much of that "steam" do you suppose is oil vapor instead
of water vapor?
I plan to let some of it condense on a cold mirror or glass
to see how greasy it is.

OC

I believe it is all water vapor, maybe some fuel vapor thrown in. I don't
believe it is oil, but your cold mirror would be a good test.

Alex Peterson
RV6-A N66AP 712 hours
Maple Grove, MN


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alexpeterson(at)earthlink
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PostPosted: Sun Feb 05, 2006 6:14 pm    Post subject: Engine Cowl Temperatures Reply with quote

Quote:

--> <gwbraly(at)gami.com>


Keep in mind that if you get the oil hot enough on each
flight to boil off the water in the oil - - then opening the
dip stick filler tube appears to accomplish very little.

Definitely off the electric topic, but:

In my case, it certainly does "appear" to be removing moisture when I watch
it. How much, I don't know, but there is a nice stream coming up for
several minutes. Some have said that bugs and things might go in there. Do
those folks check up inside the breather tube before each flight, as that is
always open? Obviously, I wouldn't leave it open if I park out in the
woods.

In the case of my plane, this steam "chimney" will happen regardless of how
long and hot the oil has been. The exhaust blow-by is constantly
resupplying the crankcase with moisture. The oil doesn't have to be at the
boiling point of water (for that altitude) in order to drive the water out,
but it obviously helps. What is known is that the higher the oil
temperature is above the dew point of the crankcase gasses (I don't know
what this value is), the faster water will be driven out. As the oil and
engine cools down, any moisture in the crankcase gasses will condense inside
the engine once the engine/oil is at or below the dewpoint of the internal
gasses.

I make and have made no claim as to whether or not any of this matters to
the engine.

Alex Peterson
RV6-A N66AP 712 hours
Maple Grove, MN


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brian



Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

PostPosted: Sun Feb 05, 2006 8:56 pm    Post subject: Engine Cowl Temperatures Reply with quote

Alex Peterson wrote:

Quote:
I make and have made no claim as to whether or not any of this matters to
the engine.

Want to take the best care of your engine? Fly regularly, like a couple
of times a week. That will do a LOT more than opening your dipstick. It
means the oil doesn't leave your cam lobes high-and-dry and it means you
get the moisture out before it forms acid with the combustion products.

I have had a couple of engines go beyond TBO by substantial margins. The
O-320 that was in my RV-4 came out of a C-172 that was a trainer and had
been flown almost daily. It had almost 2000 hours on it when it went
into my airplane. I overhauled the engine at 2600 hours even though
compressions and oil consumption were just fine. We couldn't find
anything wrong with the engine when we tore it down.

The engine in my Comanche went almost 2400 hours. I used to fly it to
work every day and the rest of its life it flew mostly long cross
countries (8-10 hours per week).

Treat them well and fly them often. That is how you make them go beyond TBO.

--
Brian Lloyd 361 Catterline Way
brian-yak at lloyd dot com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery


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brian-yak at lloyd dot com
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I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery
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