Preheating engines: Airplane engines versus auto engines

Isn't some of the problem with cold starts not necessarily oil related but
related to piston scuffing against the cylinder walls? The aluminum pistons
have a greater coefficient of expansion than the steel cylinders and the
pistons should become a looser fit at colder temps. I'm not sure how the
rings fit into the temperature equation.
--
Best Regards,
Mike

http://photoshow.comcast.net/mikenoel


"gpaleo" wrote in message
news:1198154485.901022@athprx03...
"Matt Whiting" wrote
news

Peter R. wrote:
On 12/19/2007 12:39:10 PM, "gpaleo" wrote:
This is joke post, right????

Yes, it's a joke. You can go back to bed now.


No, 6 year-olds should be in school by mid-day, not playing on mommies
computer!

As a 6 year-old mechanical engineer of some 30 years practice and owner of
an IO-540 equiped airplane, I find it somewhat disturbing that the OP was
NOT a joke.
Anyway, pat on the back - big hug time for the courageous aviator who
started his engine at **GASP** 25 F, after careful deliberation on
aborting the flight until Summer.
Catch my drift??

Peter R. wrote:

--- clip clip --


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?

Here in the north of Europe We'll pre-heat our cars if
possible, if the temperature goes below +5 C (whatever
it is in F, around 40?).

You can force an engine to start even at -30 C, but it
means that the poor thing runs some time practically
dry of lubrication.

--

Tauno Voipio (CPL(A), flying OH-PYM, PA28RT-201T)
tauno voipio at iki fi

Tauno Voipio wrote:
Peter R. wrote:

--- clip clip --


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?

Here in the north of Europe We'll pre-heat our cars if
possible, if the temperature goes below +5 C (whatever
it is in F, around 40?).

You can force an engine to start even at -30 C, but it
means that the poor thing runs some time practically
dry of lubrication.


Really? Where does all of the oil disappear to that was there when the
engine was shut down?

Matt

Matt Whiting wrote:
Tauno Voipio wrote:

Peter R. wrote:

--- clip clip --


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?


Here in the north of Europe We'll pre-heat our cars if
possible, if the temperature goes below +5 C (whatever
it is in F, around 40?).

You can force an engine to start even at -30 C, but it
means that the poor thing runs some time practically
dry of lubrication.


Really? Where does all of the oil disappear to that was there when the
engine was shut down?

Matt

The lubrication is based on fluid between the metal
surfaces. When the oil thickens enough, it will not
get to the small spaces between the metal surfaces.

--

Tauno Voipio

"Tauno Voipio" wrote in message
...
Matt Whiting wrote:
Tauno Voipio wrote:

Peter R. wrote:

--- clip clip --


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?


Here in the north of Europe We'll pre-heat our cars if
possible, if the temperature goes below +5 C (whatever
it is in F, around 40?).

You can force an engine to start even at -30 C, but it
means that the poor thing runs some time practically
dry of lubrication.


Really? Where does all of the oil disappear to that was there when the
engine was shut down?

Matt

The lubrication is based on fluid between the metal
surfaces. When the oil thickens enough, it will not
get to the small spaces between the metal surfaces.

--

Tauno Voipio

Research will tell you the oil is allready there and being cold and thick it
tends to go nowhere and in fact does its job rather well. Many engines are
started a far colder temps regularly and suffer no damage and make TBO.
Far,far worse to let an engine sit.

On Thu, 20 Dec 2007 19:39:17 GMT, Tauno Voipio
wrote:

Matt Whiting wrote:
Tauno Voipio wrote:

Peter R. wrote:

--- clip clip --


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?


Here in the north of Europe We'll pre-heat our cars if
possible, if the temperature goes below +5 C (whatever
it is in F, around 40?).

You can force an engine to start even at -30 C, but it
means that the poor thing runs some time practically
dry of lubrication.


Really? Where does all of the oil disappear to that was there when the
engine was shut down?

Matt

The lubrication is based on fluid between the metal
surfaces. When the oil thickens enough, it will not
get to the small spaces between the metal surfaces.

Preheating a car at +5C is just ridiculous if you are using the proper
weight of motor oil. I might use a block heater if the temperatures
went below -20C, but not higher than that. Try using a good 10W30 oil
between +5 and -10, and perhaps a 5W30 below that. You won't damage
anything, and your engine will last longer than the body panels on the
car!
--
Jay (remove dashes for legal email address)

Preheating a car at +5C is just ridiculous if you are using the
proper
weight of motor oil. I might use a block heater if the temperatures
went below -20C, but not higher than that. Try using a good 10W30 oil
between +5 and -10, and perhaps a 5W30 below that. You won't damage
anything, and your engine will last longer than the body panels on the
car!

I use 5W30 year-round in my '01 Chevy. Runs just fine, and
it's what the manufacturer recommends for our climate. The tolerances
in these auto engines are now so small that anything heavier is not
only a waste of time but could be really bad in the cold.
Aircraft engines have much larger tolerances, mostly because
they're air-cooled and get a lot hotter, with clearances between
things like aluminum pistons and steel cylinders getting pretty tight
at high temps. Aluminum expands at twice the rate of steel, and while
some pistons have steel inserts cast into them to control that
expansion, they still expand a lot. Liquid-cooled engines can be built
much tighter. And auto engines have much smaller cylinders than
aircraft engines of the same HP and so the overall expansion is less.
Rings are either chomed steel or cast iron and will expand at around
the same rate as the cylinder, but they'll still get tighter from the
heat draining off the piston through them. They have a bit of
difficulty getting rid of that heat through the microscopic oil film
on the cylinder wall.
With larger tolerances, more oil escapes. With larger
tolerances, the arc of contact area is shorter. With larger
tolerances, things tend to strike each other harder. So heavier oils
are necessary to slow the oil's escape from bearings and so on,
heavier to lubricate the shorter contact arcs, heavier to dampen the
shocks of parts banging into other parts.
Piston scuffing often happens when an engine is driven to full
power too soon. Pistons get hot and cylinders are still cool,
clearances disappear. Scuffing can happen if the oil isn't reaching
the cylinders, and since it's usually thrown off the rods (some
engines have a squirt hole in the rod opposite), a really low idle
might leave the cylinders dry. Some two-strokes like the aircooled
Rotaxes must be warmed up thoroughly or they'll seize soon after
takeoff. Local guy learned that the hard way. Seized it twice before
someone clued him in.

Best things for folks who fly infrequently include installing
a preoiler and don't make short flights. The preoiler will fill all
the oil galleries and pressure will come up even before start. The
short flights leave water in the oil the eat the engine. The folks who
"run it up once in a while to keep it healthy" without flying it are
doing the worst damage by far.

Dan

Tauno Voipio wrote:
Matt Whiting wrote:
Tauno Voipio wrote:

Peter R. wrote:

--- clip clip --


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?


Here in the north of Europe We'll pre-heat our cars if
possible, if the temperature goes below +5 C (whatever
it is in F, around 40?).

You can force an engine to start even at -30 C, but it
means that the poor thing runs some time practically
dry of lubrication.


Really? Where does all of the oil disappear to that was there when
the engine was shut down?

Matt

The lubrication is based on fluid between the metal
surfaces. When the oil thickens enough, it will not
get to the small spaces between the metal surfaces.


There was oil in those spaces when the engine was shut down and it
doesn't magically disappear. Most engines will run for some time with
no oil pressure and without damage.

Matt

Peter R. wrote:

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 think you made the right judgment call.

The engine life is more dependent on your long-
term level of care than for a single instance
of pressing the limits.

BTW, a simple overhand knot in the power cord
where the heater plug and the extension cord
mate will prevent someone from inadvertently
unplugging them.

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?

On 12/19/2007 1:09:15 PM, Jim Stewart wrote:

BTW, a simple overhand knot in the power cord
where the heater plug and the extension cord
mate will prevent someone from inadvertently
unplugging them.

Unfortunately no room for an overhand knot. There is no slack at all in the
Tanis heater-side plug, as it is secured right at the plug to the (IIRC)
support that also holds the fuel lines.

--
Peter