How cold is too cold to start

brien23

brien23

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Brien
How cold is too cold to start a engine with 100 weight oil, 80 weight oil, multi weight oil at what point do you use preheat. How long do you use preheat like a heated air into the engine compartment below 40-F below 32-F below 20-F below 10F below 0-F.
 
Flight school's sit outside and they usually preheat them when it's below 40*, or I'll do it myself. Mobile unit, stick the hose into the cowling for 10 minutes. Planes crank right up.
 
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Anytime the temp goes below 40F ours get preheated.
 
If the overnight temperature is above 28 and the pull it out of the hangar for take off temperature is 45, then I start it without preheat.

Once I start it, I like to see movement of the oil temperature hand before take off.
 
Lycoming and Continental both have published cold start service letters that discuss temperature minimums, preheat requirements, and oil types. Read the one that applies to your engine.
 
it's 20F or below for continental


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I pre heat below 40, anything below that ,my airplane is a real PITA to start,without preheat.like to get the oil above 50 when starting.
 
I’ll turn on my preheater for at least 5 hour before I fly if temps are below 35 F. Sometimes I get into locations where preheating is not practical and I’ll start without, but I’ll never attempt it below 20F. I got a homemade campstove heater to use if temps are too low but it is a real PITA.
 
Hmm. I preheat per manufacturer's recommendations. If I preheated at 50* I'd preheat 9 months of the year!
 
Stewartb said:
Lycoming and Continental both have published cold start service letters that discuss temperature minimums, preheat requirements, and oil types. Read the one that applies to your engine.
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Continental has only one letter that I can find, applicable to all engines. SIL 03-1 It says to preheat if cold-soaked below 20 F for 2+ hours, and it expresses some thoughts about how to start a non-preheated engine between 20 F and 40 F.
 
Stewartb said:
Hmm. I preheat per manufacturer's recommendations. If I preheated at 50* I'd preheat 9 months of the year!
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Okay, let me qualify that: I don't preheat just because the overnight temp drops below 50F. Only if the ambient temp for most of the morning before planned departure is < 50F. I figure exposed metal will equilibrate to ambient fairly quickly, and then conduction will bring the cylinders to roughly the same temp. I rarely leave in the early morning anyway. That means no preheat needed for about 7-8 months out of the year. The other months, I fly much less anyway, so I'm not using the preheater *that* much.

Though, I don't pay the electric bills here, and my hangar rent is the same regardless, so it's not really a factor for me.
 
Granted that while there are differences in engine construction would anyone buy a car with an engine that needed to be preheated? I think not.

For the record, I have been in situations where I needed to cold start a plane. No damage resulted from doing that. When I had to do so I let the engine run at idle speed for a bit before applying power.
 
The bottom of the green for my engine oil temp is 70*. I don’t apply taxi power until I see that and it doesn’t take very long when the engine is started at 25* or so. In that time I’m waiting for the muffler to provide some defrost heat anyway since windows fog quickly in a cold plane with a warm human inside. I know lots of guys that use 32* as a preheat threshold. There’s no evidence that I’ve seen that supports that limit but it won’t hurt anything, either. My little Odyssey battery spins my big Continental to life easily down in the mid-20s but it takes lots of prime to do it. Below that temp? There’s a fine line between adequate prime and flooding. And THAT’s why I preheat.
 
let me leave this right chair....note the differences between Aluminum and steel, major engine components in aircraft engines. :D
gf_thermal_expansion.jpg
 
So for my engine that operates in the 400* range and starts in average temps around 50* and down to manufacturer’s published limits at 20*.... how much different are the engine tolerances at 20* and your preferred 40*? Since the manufacturer has done virtually all the engineering and testing, provides warranty, and accepts liability for their products... what do you offer that outweighs what they say? I don’t have a particular objection to anyone preheating. My question is why you think your practices are better? What evidence do you have. Not internet BS smoke and mirrors, but real evidence?
 
It’s a table of values. How does it apply to my specific question?
 
Stewartb said:
It’s a table of values. How does it apply to my specific question?
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well....what are these parts made from? ...and what temps are the parts designed to? What about the extremes?....what about the tolerance stackup?
 

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45 and below I’m sending a text to the hangar switchbox and turning on the preheats, oil and cylinders. During the winter months I always plug in and cover cowl and prop with moving blankets.
 
Stewartb said:
The bottom of the green for my engine oil temp is 70*. I don’t apply taxi power until I see that
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Out of curiosity, is that published, or just a personal presence. All of my airplanes will taxi at less than 1000 rpm. My Beech 18 has published min temp for runup and min temp for takeoff and flight but I’ve never seen a minimum taxi temp.
 
Stewartb said:
So for my engine that operates in the 400* range and starts in average temps around 50* and down to manufacturer’s published limits at 20*.... how much different are the engine tolerances at 20* and your preferred 40*? Since the manufacturer has done virtually all the engineering and testing, provides warranty, and accepts liability for their products... what do you offer that outweighs what they say? I don’t have a particular objection to anyone preheating. My question is why you think your practices are better? What evidence do you have. Not internet BS smoke and mirrors, but real evidence?
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You're cruising at 400f CHT? Do you have louvers or anything?

Normally I lean and cowl flap for 380 climb and 350 cruise
 
Fearless Tower said:
Out of curiosity, is that published, or just a personal presence. All of my airplanes will taxi at less than 1000 rpm. My Beech 18 has published min temp for runup and min temp for takeoff and flight but I’ve never seen a minimum taxi temp.
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Whether on tires or wheel skis it takes generous application of throttle to move my plane out of the gravel tie down and along the gravel and sand taxi area. Maybe more important is that my average taxi length is about 600', so there's not much warming to do during taxi. My Cessna oil temp green range starts at 70*. My SAP IO-400 low green is 75*. I usually want to see 275* CHT before pulling out of parking and with that oil and cylinder temps are good to go at about the same time.
 
Checkout_my_Six said:
let me leave this right chair....note the differences between Aluminum and steel, major engine components in aircraft engines. :D
gf_thermal_expansion.jpg
Click to expand...
So, just to be clear you don’t think the engine manufacturers considered dissimilar metals and clearances inside the engine when they made recommendations for cold weather operations and you know enough about said clearances and engine design work that you are willing to throw your engineering around to justify a warmer temp than the manufacturer recommended.

If you said you like preheating at a warmer temp than manufacturer recommends because you are a conservative owner and you want to do everything possible to ensure long engine life then I would agree with you. But to imply that others are hurting their engines by following guidance from the manufacturer is a bit of a stretch. You haven’t presented enough information to corroborate your statements.
 
my truck doesn't have to be plugged in during my winter months, but it makes it nice to have heat in the cab much quicker when it is.
It does start much quicker when plugged in...I usually plug in if temps go below 0F.

Oh, and just to keep it aviation-related, our club policy is to plug in our planes while hangared when temps are 40F or below.
 
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I can count my truck plug-in days for the past 25 year on one hand. Starting those at -40*F is without heat is simple, even with diesels. At -45* for a few days the diesels get too stiff but the gas motors fire right up. I recall the Duramax manual saying to plug in below -30*. Most of the time there isn't a power outlet available so we do without. My trucks use 5-30 synthetic oil and my other 4-cycle equipment uses 0-30. But that has little to do with starting an air cooled airplane engine.
 
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Tarheelpilot said:
So, just to be clear you don’t think the engine manufacturers considered dissimilar metals and clearances inside the engine when they made recommendations for cold weather operations and you know enough about said clearances and engine design work that you are willing to throw your engineering around to justify a warmer temp than the manufacturer recommended.

If you said you like preheating at a warmer temp than manufacturer recommends because you are a conservative owner and you want to do everything possible to ensure long engine life then I would agree with you. But to imply that others are hurting their engines by following guidance from the manufacturer is a bit of a stretch. You haven’t presented enough information to corroborate your statements.
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yup.....I'd avocate warmer startups are less wear and more better for all the moving parts.

A good friend of mine was a Lycoming engineer and for grins did a stackup analysis of an old design and discovered a few things. Those "things" never made it to the marketing glossy documents. The first was the "possibility", a remote one but, none the less, possibility of spinning a main bearing due to a cold thermal interference. The parts have to be mixed and matched just right on a "new" engine....but mathematically he was able to have metal to metal contact on the front main journal bearing....enough for it to spin ....at temps around 32 F. An older engine, one with wear, wouldn't have this issue. Another discovery was the possibility of a thermal induced line-to-line or metal contact in the choke area of the cylinder with the piston & rings. All due to differences in thermal expansion or coefficient of thermal expansion between steel and aluminum parts.

The second observation is well known and the evidence can be observed when tearing down tired cylinders....
 
Checkout_my_Six said:
yup.....I'd avocate warmer startups are less wear and more better for all the moving parts.

A good friend of mine was a Lycoming engineer and for grins did a stackup analysis of an old design and discovered a few things. Those "things" never made it to the marketing glossy documents. The first was the "possibility", a remote one but, none the less, possibility of spinning a main bearing due to a cold thermal interference. The parts have to be mixed and matched just right on a "new" engine....but mathematically he was able to have metal to metal contact on the front main journal bearing....enough for it to spin ....at temps around 32 F. An older engine, one with wear, wouldn't have this issue. Another discovery was the possibility of a thermal induced line-to-line or metal contact in the choke area of the cylinder with the piston & rings. All due to differences in thermal expansion or coefficient of thermal expansion between steel and aluminum parts.

The second observation is well known and the evidence can be observed when tearing down tired cylinders....
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Which “old design” did he do the stack up analysis on?
 
Tarheelpilot said:
Which “old design” did he do the stack up analysis on?
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IO-540.....but, they all are very similar in the stackup.

We aren't seeing airplanes fall out of the sky because of cold starts.....IMHO it just makes good practice to pre-heat....and I choose 40 deg F as my comfort or safety factor.
 
Stewartb said:
Whether on tires or wheel skis it takes generous application of throttle to move my plane out of the gravel tie down and along the gravel and sand taxi area.
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That makes sense. I’m based on pavement, so taxiing is a little different for me. I usually end up getting to the runup area and waiting for the several gallons of oil to come up to temp.
 
gkainz said:
my truck doesn't have to be plugged in during my winter months, but it makes it nice to have heat in the cab much quicker when it is.
It does start much quicker when plugged in...I usually plug in if temps go below 0F.

Oh, and just to keep it aviation-related, our club policy is to plug in our planes while hangared when temps are 40F or below.
Click to expand...

I might talk to who ever made that policy if I were you, I don't think any of the engine manufactures recommend that, and making things up as you go isn't a good idea.
 
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