How cold when you do not preheat engine

blueskyMD

blueskyMD

Pre-takeoff checklist
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Bigfoot297
Or I should ask how much warm the air should be when you do not bother to preheat the engine. Well I have to fly on Friday night -late night when FBO will be closed and my Red Dragon pre heater is broken. Temperature at that time is supposed to be around 35.I use Phillips 20 W50 oil and of course I will use cold starting procedures including starting at low RPM. I know Lycoming says its OK to start engine if its above 20 degrees but I have never started motor less than 45 d OAT. What you guys think ? especially those who flew pistons for living at some point in their lives,I would love to hear their views.
 
Most Lycomings are okay to start down to 10* (according to Lycoming). I preheat when convenient but when not convenient? I'll start either brand at 20*. Maybe colder if the situation requires.
 
Why not get an extension cord and place a couple of 100 watt bulbs in the cowling? It works fine as a substitute pre-heater. Otherwise you should be fine, just allow yourself enough time to warm during the run-up.
 
blueskyMD said:
Or I should ask how much warm the air should be when you do not bother to preheat the engine. Well I have to fly on Friday night -late night when FBO will be closed and my Red Dragon pre heater is broken. Temperature at that time is supposed to be around 35.I use Phillips 20 W50 oil and of course I will use cold starting procedures including starting at low RPM. I know Lycoming says its OK to start engine if its above 20 degrees but I have never started motor less than 45 d OAT. What you guys think ? especially those who flew pistons for living at some point in their lives,I would love to hear their views.
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35F and a multi-grade oil? I think you'll be fine starting it up without heat.
 
I had a hell of a time starting the IO-540 just above freezing. Should have been easy.

No preheat. Nobody even has those here. I ended up flooding it, but I did get it started.

It doesn't usually get that cold here, but it did over the last 5 days or so.

Aircraft was outside, and I started it just as soon as the frost melted off.
 
Ryanb said:
Why not get an extension cord and place a couple of 100 watt bulbs in the cowling? It works fine as a substitute pre-heater. Otherwise you should be fine, just allow yourself enough time to warm during the run-up.
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No access to outlet she is on ramp otherwise I do have engine heater installed
 
I remember reading someone where conti recommended preheating sub 40f.

I try, actually my plane has a oil dilution system, never needed it, but shy of some bad stuff, I wouldn't really want to play around below freezing.
 
Starting my Lycoming 320 is a PITA below 50 deg.
 
blueskyMD said:
No access to outlet she is on ramp otherwise I do have engine heater installed
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You at ABE, or Queen City? Someone friendly must have a hangar with an outlet that you could tap.
 
Usually below 40. Certainly helps. I cringe at the guys just cranking their starter over and over on the ramp on a cold morning.
 
James331 said:
I remember reading someone where conti recommended preheating sub 40f.

I try, actually my plane has a oil dilution system, never needed it, but shy of some bad stuff, I wouldn't really want to play around below freezing.
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My buddy (not Ted, but, Ted knows him), a former engineer for Lycoming, did a tolerance stack up analysis and discovered that there is a "possibility" of interference fit between several of the crank bearings and the crank....and in the choke area of the cylinder and piston at or below 40 degrees F.

That's enough info for me to take precaution....:D
 
172andyou said:
Then there's your answer.

Even more so if this is a rare event.
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True but Lycoming does not have to pay if things get broken down the road. More importantly I fly a lot at night over hostile terrain and I want to make sure I am doing as much as possible to take care of my engine. For this particular flight as some of you mentioned I believe I will be fine. I was curious if someone had heard of reports of any engine issues which manufacturers did not take into account
 
Checkout_my_Six said:
My buddy (not Ted, but, Ted knows him), a former engineer for Lycoming, did a tolerance stack up analysis and discovered that there is a "possibility" of interference fit between several of the crank bearings and the crank....and in the choke area of the cylinder and piston at or below 40 degrees F.

That's enough info for me to take precaution....:D
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Yet clearances are reduced when the engine gets hot...
 
GlennAB1 said:
Yet clearances are reduced when the engine gets hot...
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Ummm....some are....some are not. Remember we have different materials and different coefficients of thermal expansion. Aluminum and steel don't contract equally when cold.

Guess what temps the designs are tollerenced at? ....a temp where the metrology lab can accurately measure them....but designed for optimal clearance at operational temps
 
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A lot depends on the oil's viscosity. A multigrade will flow at considerably lower temperatures than W80, for instance. Take a quart of your oil and put it in the fridge freezer overnight. Stick a thermometer in there, too. Then see how easily it pours, and imagine the engine's oil pump trying to suck it up the pickup tube. If it can't pull it easily, your engine doesn't get much oil--maybe none--for the first while. That's a good way to trash the engine.
 
Under 40 I would but if out on a ramp overnight somewhere I wouldn't be afraid to try to start it in colder weather. The main limiting factor is I find my plane is darn near impossible to get started when the temp is significantly below freezing without any preheat.
 
Checkout_my_Six said:
Ummm....some are....some are not. Remember we have different materials and different coefficients of thermal expansion. Aluminum and steel don't contract equally when cold.

Guess what temps the designs are tollerenced at?
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The steel cylinder will contract at almost exactly half the rate that the aluminum piston will. More room, therefore, when cold. The steel rods will shrink at the same rate as the steel crankshaft. Valve guides will shrink more than the valve stems, but the diameters are so small it wouldn't be much issue.
 
blueskyMD said:
No access to outlet she is on ramp otherwise I do have engine heater installed
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Before I moved to a hangar I had to run three hundred feet of extension cord to power the preheats. That was a pita but if I wanted to fly that's what had to be done.
 
GMascelli said:
Before I moved to a hangar I had to run three hundred feet of extension cord to power the preheats. That was a pita but if I wanted to fly that's what had to be done.
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Going out and acquiring 300' of extension cords to do a single startup on a 35F day is a bit excessive.
 
Dan Thomas said:
The steel cylinder will contract at almost exactly half the rate that the aluminum piston will. More room, therefore, when cold. The steel rods will shrink at the same rate as the steel crankshaft. Valve guides will shrink more than the valve stems, but the diameters are so small it wouldn't be much issue.
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what material is on the outside of the steel cylinder in the choke area?...that's where clearance is lost. :eek:
 
I'll preheat below 30 no matter how much of a pain my club's red dragon is...
 
Checkout_my_Six said:
Ummm....some are....some are not. Remember we have different materials and different coefficients of thermal expansion. Aluminum and steel don't contract equally when cold.

Guess what temps the designs are tollerenced at? ....a temp where the metrology lab can accurately measure them....but designed for optimal clearance at operational temps
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Interesting.
http://www.avweb.com/news/maint/182846-1.html
 
In Alaska we put on the engine blankets and plugged in the heaters when the temp was forecast to be below 32f. Check the oil and see if it drips off the dip stick. If not, add heat.

Get one of those electric charcoal starters and put it under the cowling. Just be sure not to touch it to any thing that will burn or melt. I just laid one on the front cylinder fins, then put an old piece of carpet over the top of the cowling. That seemed to work to at least 10f.

Plan for a longer warm up after starting.
 
Although the engine may be fine at those temps, I don't think *this* pilot would!!
 
Fearless Tower said:
In relation to the OP's specific question, it looks like Mike Busch refers to 32F as the cold start cutoff.
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True, but, in relation to the response by Checkout_my_Six, Mike Busch used some far extremes to come up with a possible interference fit condition. -20F and minimal clearance at overhaul.
 
GlennAB1 said:
True, but, in relation to the response by Checkout_my_Six, Mike Busch used some far extremes to come up with a possible interference fit condition. -20F and minimal clearance at overhaul.
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Damn.... what about human clearance overhaul?? Below 50 I don't venture outside.
 
45 or below and I plug it in, 35 and below I pull the sunbeam ceramic out for the cockpit 30 min before departure. That last step is as much for me as it is for the gyros ...
 
Question.

How long does it gereally take to preheat the engine once it's plugged in?

Ditto if you use the external heater/ heat lamp.
 
korben88 said:
Question.

How long does it gereally take to preheat the engine once it's plugged in?

Ditto if you use the external heater/ heat lamp.
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Don't know....mine is plugged in and blanketed up the night before and is toasty warm in the morning....using just an oil pan heater. The complete engine cell/cowling area is above 70 with an OAT in the teens.
 
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