Preheating engines: Airplane engines versus auto engines

On Dec 19, 12:21 pm, "Peter R." wrote:
This time of year here in the Northeast US I always preheat my Bonanza's
IO520 engine with a Tanis heater and an insulated cowling/prop cover as it
sits in an unheated t-hangar. The result is that the oil temperature at
startup is around 105 degrees F, even if the outside air temperature is as
low as -15 degrees F.

Monday night I arrived at my t-hangar to discover that at some point during
the day the line person accidentally pulled out the plug connecting the Tanis
heater to the small extension cord I use to extend the plug to the outside of
the cowling cover, so the aircraft had not been preheating. Outside and
inside temperatures were both a cold 25 degrees F.

Given any other day, I would have plugged the aircraft back in and scrapped
the flight but in this case I had an Angel Flight patient waiting in another
city for my arrival and I was already late. Thus I made the painful decision
to start up the aircraft and allow it to low idle until the oil heated
thoroughly. A small consolation is that the engine had been recently filled
with fresh Exxon Elite oil. To my relief the aircraft started right up.

I know what I did has negative long term repercussions on my engine's health
and I have already derived a tool to lock the two cords and prevent this
accidental unplugging from happening again. However, this leads me to
question the differences between aircraft engines and auto engines:

Why is it that here in the Northeast US seemingly no one preheats their
automobile engine before start-up in very cold temperatures? Is the long-term
damage the same for both autos and aircraft engines? If so, why do you
suppose auto owners don't typically do this? Is it because that most auto
owners do not keep their cars very long?

--
Peter

My understanding is that the _oil_ is different, not the engine. Most
piston aircraft engine oils gel at higher temperatures than do oils
for automotive engines. Or at least that is what I was told by my
instructor when I was training up in the high country.

Don't be relieved that the engine started. Be relieved that there
isn't anything ferrous in the oil screen next annual inspection.
Might ask your neighborhood FBO to use one of their portable heaters
next time around :-)

-Psy

On 12/19/2007 1:51:18 PM, " wrote:

Might ask your neighborhood FBO to use one of their portable heaters
next time around :-)

I have read in several different mags that those portable heaters only warm
the cylinders and not the bottom end (cam shaft) where the heated oil is most
important during the short time most FBOs run the units. Consequently it is
somewhat a waste of time and energy to use that type of heater.

--
Peter

Peter R. wrote:
On 12/19/2007 1:51:18 PM, " wrote:

Might ask your neighborhood FBO to use one of their portable heaters
next time around :-)

I have read in several different mags that those portable heaters only warm
the cylinders and not the bottom end (cam shaft) where the heated oil is most
important during the short time most FBOs run the units. Consequently it is
somewhat a waste of time and energy to use that type of heater.



I use both.

I plug in the pan, while at the same time using a forced air unit.

On Dec 19, 11:57 am, "Peter R." wrote:
On 12/19/2007 1:51:18 PM, " wrote:

Might ask your neighborhood FBO to use one of their portable heaters
next time around :-)

I have read in several different mags that those portable heaters only warm
the cylinders and not the bottom end (cam shaft) where the heated oil is most
important during the short time most FBOs run the units. Consequently it is
somewhat a waste of time and energy to use that type of heater.

--
Peter

If you heat the cylinders you'll heat the whole engine.
Metal conducts heat.

25°F isn't cold unless you're running heavy oil, like
W100. We run Aeroshell 15W50 year-round and sometimes start these
things at -10°C which is what? around 14°F? And the engines
(Lycomings) all reach TBO. No metal. We put cowl covers on them after
a flight when they're parked outside and start them later on at temps
to -25°C.

The big danger with cold oil is its reluctance to flow.
The oil pump has to suck the oil up from the sump, and cold oil gets
thick. It's like trying to suck a cold, thick milkshake through a
straw; you've all done that. The pump cannot create more than an
absolute vacuum, and if the oil is too thick the pump won't get much
and so the engine won't get it either. The cylinders don't mind
getting little, but the bearings need lots and so does the cam. Idling
too fast will cavitate the pump, delivering no or too little oil.
Idling too slow will throw too little oil on the cams and into the
cylinders. Can get tricky.

More likely damage is burning out starters from long
cranking. Or overpriming and flooding the engine. Or having it run
only briefly and quit, whereupon those cold sparkplugs will frost over
(H2O in the combustion byproducts) and the frost shorts them out. No
more spark. Burn out the starter trying to make it go. Starters have
no cooling system. Starter manufacturers say that a five-minute
cooldown is required after three ten-second cranks.
Kill the battery, and as the acid turns to water as it
discharges, the battery will now freeze (if it's cold enough and the
battery is dead enough and you leave it in the airplane) and split and
spill weakened acid everywhere. It'll still eat your airplane.

Cars typically use 5W30. I used to use 0W30 in my Ford
pickup. Started OK at -35°C. Airplane engines can't use such thin
stuff.

Dan

On 12/19/2007 7:56:55 PM, wrote:

Cars typically use 5W30. I used to use 0W30 in my Ford
pickup. Started OK at -35°C. Airplane engines can't use such thin
stuff.

Thanks, Dan, for the education. Unlike some of the hotshot pilots in this
group who apparently were born with this knowledge, I admit to still having a
lot to learn despite flying twice to three times every week.

--
Peter

"Peter R." wrote in message
...
On 12/19/2007 7:56:55 PM, wrote:

Cars typically use 5W30. I used to use 0W30 in my Ford
pickup. Started OK at -35°C. Airplane engines can't use such thin
stuff.

Thanks, Dan, for the education. Unlike some of the hotshot pilots in this
group who apparently were born with this knowledge, I admit to still
having a
lot to learn despite flying twice to three times every week.


FWIW - http://www.reiffpreheat.com/tbo.htm

And some magazine articles at
http://www.reiffpreheat.com/product.htm#Why_preheat

And a blog article about engine moisture after shutdown (and follow-up) at
http://www.reiffpreheat.com/product.htm#Why_preheat (2nd and 3rd down)

As always...YMMV.
--
Matt Barrow
Performance Homes, LLC.
Cheyenne, WY

Peter R. wrote:

Why is it that here in the Northeast US seemingly no one preheats their
automobile engine before start-up in very cold temperatures? Is the long-term
damage the same for both autos and aircraft engines? If so, why do you
suppose auto owners don't typically do this? Is it because that most auto
owners do not keep their cars very long?


Well, I make no claim to KNOW the answer, but I do have a few opinions
about it.

1. Auto engines have tighter tolerances as they are water cooled and
operate over a narrower and better controlled temperature range. They
can thus run thinner oil which starts to circulate much more quickly
than the molasses specified for most aircraft engines.

2. The consequences of engine damage in a car are much lower so it just
isn't worth the hassle of using an engine heater unless it is required
for the car to start.

3. This is a perpetuation of a decades old myth.

I personally believe that the above are weighted roughly as follows:

1. 30%
2. 10%
3. 60%

It would fun to have real data, but that would be very expensive and
time consuming to obtain. I've run many car engines well above 100,000
miles (roughly time equivalent to 2,000 hours, but not total power
produced equivalent to an airplane engine) with cold starts at least 5
months of the year and never had any indication of unusual engine wear.
I've NEVER yet worn out an auto engine in 30+ years of auto ownership.


Matt

On Dec 19, 4:40 pm, Matt Whiting wrote:
Peter R. wrote:
Why is it that here in the Northeast US seemingly no one preheats their
automobile engine before start-up in very cold temperatures? Is the long-term
damage the same for both autos and aircraft engines? If so, why do you
suppose auto owners don't typically do this? Is it because that most auto
owners do not keep their cars very long?

Well, I make no claim to KNOW the answer, but I do have a few opinions
about it.

1. Auto engines have tighter tolerances as they are water cooled and
operate over a narrower and better controlled temperature range. They
can thus run thinner oil which starts to circulate much more quickly
than the molasses specified for most aircraft engines.

2. The consequences of engine damage in a car are much lower so it just
isn't worth the hassle of using an engine heater unless it is required
for the car to start.

3. This is a perpetuation of a decades old myth.

I personally believe that the above are weighted roughly as follows:

1. 30%
2. 10%
3. 60%

It would fun to have real data, but that would be very expensive and
time consuming to obtain. I've run many car engines well above 100,000
miles (roughly time equivalent to 2,000 hours, but not total power
produced equivalent to an airplane engine) with cold starts at least 5
months of the year and never had any indication of unusual engine wear.
I've NEVER yet worn out an auto engine in 30+ years of auto ownership.

Matt

Matt's answer is right on. My experimental plane has a V-8 347 cu in
all aluminum water cooled engine in it. I keep it in a 50 f hangar, it
has a oil pan heater that cycles at 165 f and it loves it, I run 10-40
racing oil and the oil pressure comes right up on start up. Aircooled
engines spec 100w which is really straight 50 weight, the multi
viscosity aircraft oils are still alot thicker then automotive oils so
they take longer to suck up through the pick up tube and pressurize
the oil galley. As for the original poster I am sure he didn't do any
harm to his motor by starting it at 25 f.

Ben
www.haaspowerair.com

Matt's answer is right on.

Ah, yes, the annual "Is it necessary to pre-heat?" thread. Soon to
be followed by the "Should I leave it plugged in all the time?"
discussion!

Just to get the ball rolling, we pre-heat Atlas whenever the temp is
below 40 degrees F. And, yes, we leave it plugged in all the time.
("It" being a Tanis oil pan and cylinder head heater with a quilted
nose cowl wrap to hold the heat in...)

Here's a pic of our cowl wrap, custom made by Mary from an old nylon
sleeping bag and a bunch of velcro:
http://tinyurl.com/2oj9g7

We fly at least weekly, so I don't worry about condensation. IMHO,
plugging in the heater immediately after shut-down should help to
prevent condensation from developing, since the engine never cools
back to ambient temperature before it's started and brought back up to
temperature at the next flight.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Hi Jay!

Kinda feels like the other "home" doesn't it !?



Dave



On Wed, 19 Dec 2007 16:57:53 -0800 (PST), Jay Honeck
wrote:

Matt's answer is right on.

Ah, yes, the annual "Is it necessary to pre-heat?" thread. Soon to
be followed by the "Should I leave it plugged in all the time?"
discussion!

Just to get the ball rolling, we pre-heat Atlas whenever the temp is
below 40 degrees F. And, yes, we leave it plugged in all the time.
("It" being a Tanis oil pan and cylinder head heater with a quilted
nose cowl wrap to hold the heat in...)

Here's a pic of our cowl wrap, custom made by Mary from an old nylon
sleeping bag and a bunch of velcro:
http://tinyurl.com/2oj9g7

We fly at least weekly, so I don't worry about condensation. IMHO,
plugging in the heater immediately after shut-down should help to
prevent condensation from developing, since the engine never cools
back to ambient temperature before it's started and brought back up to
temperature at the next flight.