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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 |
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Preheating engines: Airplane engines versus auto engines
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 |
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Preheating engines: Airplane engines versus auto engines
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. |
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Preheating engines: Airplane engines versus auto engines
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 |
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Preheating engines: Airplane engines versus auto engines
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 |
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Preheating engines: Airplane engines versus auto engines
"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 |
#7
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Preheating engines: Airplane engines versus auto engines
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 |
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Preheating engines: Airplane engines versus auto engines
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 |
#9
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Preheating engines: Airplane engines versus auto engines
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" |
#10
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Preheating engines: Airplane engines versus auto engines
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. |
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