Cold Starts

The threat of the aluminum case shrinking to the point of seizing onto the
steel crank due to the differential in expansion rate of the two materials
is more theoretical than real... Ignored is the fact that the bearing shells
are steel cylinders and will compress only so much when the case shrinks,
else they would buckle and collapse...

The argument of "it is the liquid cooling that makes the difference",
ignores the engineering fact that modern liquid cooled engines have vastly
tighter clearances than air cooled engines, not the other way around... So,
low temperature starts should be a hundred times more damaging to the engine
on your car by that theory... Yet my aluminum block/steel crank automobile
engine, which has such tight clearances that the owners manual calls for a
5W20 as the standard oil, - I actually use 10W30 - started the other
morning at -14F yup, 14 below and is still running fine, no knocking, no
oil smoke, no crushed bearing shells, etc...

As I spoke about in my diatribe on preheating, yesterday; most of what is
passed from cfi to student is an old wives tale endlessly repeated... And
yes, some of those OWT's find their way into the pilots handbook from
engineers who ought to know better...

As far as the comment about cylinder choke - yup, it exists - but come on
guys, think!... The cylinder sleeve is steel, the piston is aluminum... So
the piston will shrink more than the cylinder at very low temperatures, not
the other way around... There is no interference fit and no binding on start
up...

Let me post a challenge... Who knows of an engine that was actually damaged
and had to be overhauled because of cold starts without a preheat? Nope,
not the story of a guy I know told me about so and so... What engine do you
have first hand knowledge of, that was burned up on your airfield because of
a cold start? Doesn't exist!

I can start my engine every morning all winter long with no preheat, and you
start your engine once every two weeks with preheat, and I will have less
wear on my engine than you will...
denny

wrote in message
...
Dave Stadt wrote:
: How come the engine in my car with 190,000 miles is running fine with no
: signs of undue wear with nary a single preheat. It is often started at
: temps well below 0 F. Aluminium block, steel crank, steel cylinder
liners
: and aluminium pistons same as the ole Continental.

Two words: Liquid cooling. Everything about the aircraft engine is
catered to
running at ridiculously high temperatures during normal operation. The
oil is very thick
so it still lubricates at high temperatures and carries heat away from the
cylinders. The
cylinders themselves have choke (they're slightly smaller bore at the
top), with the
thought being they'll expand to be straight when they heat up during
normal operation.
Those two things are the primary reasons.... lack of oil and scuffing of
cylinders.

-Cory

--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************

Wasn't that the basis for a song about a beautiful woman and a desperate
man?
denny

"Doug" wrote in message
om...
Well,,,desperate men do desperate things.

No No!
Ground running is NOT good for an engine. Uneven cooling, you know!

Take it up for a 1 hour FLIGHT each four hours!

That's the PROPER way to keep it warm.

Rich

Doug wrote:

Well,,,desperate men do desperate things.

Stay at a motel near the airport and go out and start your plane and
run it for 1/2 hour every 4 hours. Bring the walkman.

Exactly!
denny

"Dave Stadt" wrote in
How come the engine in my car with 190,000 miles is running fine with no
signs of undue wear with nary a single preheat. It is often started at
temps well below 0 F. Aluminium block, steel crank, steel cylinder liners
and aluminium pistons same as the ole Continental.

Dennis O'Connor wrote:

As I spoke about in my diatribe on preheating, yesterday; most of what is
passed from cfi to student is an old wives tale endlessly repeated... And
yes, some of those OWT's find their way into the pilots handbook from
engineers who ought to know better...

Pilot's handbooks are written by marketing departments, not engineers.

George Patterson
A diplomat is a person who can tell you to go to hell in such a way that
you look forward to the trip.

Viscosity...

"Paul Sengupta" wrote in message
...
wrote in message
...
The oil is very thick

Is there any difference in viscocity between a 15/50 aero oil
and a 15/50 car oil?

Paul

As I understood it, the max engine damage is done just after starting,
before the oil is flowing properly, both in a car engine and a plane
engine. I know when it's cold it takes longer for my oil pressure to
come up, inferring that the oil is thicker when cold...also suggesting
that the oil isn't flowing to the important bits so quickly.

So I'd have thought that pre-heating (if done properly) would
extend the life of the engine by some amount rather than prevent
catastrophic failure.

Paul

"Dennis O'Connor" wrote in message
...
Let me post a challenge... Who knows of an engine that was actually
damaged
and had to be overhauled because of cold starts without a preheat?

wrote in message
...
Dave Stadt wrote:
: How come the engine in my car with 190,000 miles is running fine with no
: signs of undue wear with nary a single preheat. It is often started at
: temps well below 0 F. Aluminium block, steel crank, steel cylinder
liners
: and aluminium pistons same as the ole Continental.

Two words: Liquid cooling. Everything about the aircraft engine is
catered to
running at ridiculously high temperatures during normal operation. The
oil is very thick
so it still lubricates at high temperatures and carries heat away from the
cylinders.

I use 15W50 in the Continental and 10W40 in the car. Not much difference.
Also, in the winter people run their Cont/Lycs on straight 30 weight. 30
weight is like water when at operating temps. I don't believe my O-200 runs
nearly as hot as a modern auto engine.

The
cylinders themselves have choke (they're slightly smaller bore at the
top), with the
thought being they'll expand to be straight when they heat up during
normal operation.
Those two things are the primary reasons.... lack of oil and scuffing of
cylinders.

Doesn't play. The pistons are aluminium and the bores are steel. In cold
weather the aluminium pistons shrink more than the steel cylinders and
clearance actually increases. The rings are steel and follow the cylinders.


-Cory

--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************

well, I've done the no-preheat thing on a 30 degree day and the prop
didn't spin all that fast (barely started). With a preheat on a
20 degree day the prop spins a lot faster. Preheating does something
for my engine.

Ditto that.

We've got the oil pan and cylinder heaters, and a cowl blanket. Pre-heat,
and the thing pops right over. Don't pre-heat, and it cranks like an old
meat grinder.

Which sounds like a friction thing to me. And I guess I always assumed that
friction was a bad thing inside an engine.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Double ditto.

I want fluid oil running all over those freezing cold engine parts. Whether
engine clearances are reduced when cold or not, metal on metal with no
lubricant can't be good.

I would not expect catastrophic failure. Just reduced engine life. Next time
I see some poor soul at the side of the road with a smoking engine, I'm
gonna think - cold engine starts.

--
-------------------------------
Travis
"Jay Honeck" wrote in message
news:CivYb.339528$xy6.1678994@attbi_s02...
well, I've done the no-preheat thing on a 30 degree day and the prop
didn't spin all that fast (barely started). With a preheat on a
20 degree day the prop spins a lot faster. Preheating does something
for my engine.

Ditto that.

We've got the oil pan and cylinder heaters, and a cowl blanket. Pre-heat,
and the thing pops right over. Don't pre-heat, and it cranks like an old
meat grinder.

Which sounds like a friction thing to me. And I guess I always assumed
that
friction was a bad thing inside an engine.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"