Reliability and complexity of alternative engines.

[akschu]

Originally Posted by SvingenB

Starting any engine in -20F is the equivalent of approximately 6 to 10hours, or more, continuous run at operating temperature regarding TBO (if there is a set TBO). A tight tollerance Subaru engine is certainly not better than a loose Lycoming in this respect.

Absolutely it is. The loose lycoming is designed to have proper piston/bore clearances when it is hot, therefore when it is cold it has very tight piston/bore clearances. The subaru engine also has tight piston/bore clearances, but not nearly as much because it has a much smaller bore and because it's not designed to operate over 250*. The bore size and temp delta force the lycoming to run much larger tolerances.

I don't see any logic in designing redundant electrical systems, and at the same time plan to regularly start the engine below 0C without a pre heater. A pre heater is simple, cheap and light weight, even the ones that runs on fuel. In cold weather, a pre-heater is the single most important item for a long lasting trouble free engine.

A pre heater is somewhat effective at getting the engine warm, but as soon as you start it the cold air will take the heat way pretty quick and the engine doesn't generate enough heat at idle to really warm it up. Any which way you look at it, you are expecting a cold air cooled engine to make rated HP at take-off even though the cylinders haven't grown enough to have the piston/bore clearances of running temps. The subaru on the other hand can be warmed up by a freeze plug and pan heater which is a simple plug in, then when you start it, it will come up to operating temp before take-off regardless of outside temp.

Perhaps you have never flown in -10F before, air cooled engines are a totally different animal, while a liquid cooled engine will act exactly the same except for the freeze plug heater to warm it up, not to mention the cab will break 30F.

schu

[rv6ejguy]

The big differences are in the oils available today for auto engines- 0W-20/30 and 5W50. These give you awesome cold cranking capability and full protection on the top end. The much closer tolerances and faster warmup in auto engines exhibit far lower wear rates during a cold start and warmup cycle.

Lots of car engines go 300,000+ km here in Canada with half the year below 0C and winter months at -20 to -30C or even colder. They last just fine. Most people don't plug in block heaters here until it dips below -20C. My record starting an engine here without being plugged in is -38C. I don't think a Lycoming would do that.

A typical 550 watt block heater will raise coolant temps from -20C to +10C in about 1 hour- pretty efficient.

Cabin heat via a heater core is far more effective than muffs and dispenses with that hot metal smell usually associated with exhaust muffs.

[Mike S]

Speaking of lubrication quality--------

How about the fact that one common thing for use in really cold climates is an oil dilution setup, where you add gasoline to the oil pan at shutdown, to lessen the drag for cold starting.

A buddy who lives in Alaska has this on his C185.

[rv6ejguy]

Originally Posted by Mike S

Speaking of lubrication quality--------

How about the fact that one common thing for use in really cold climates is an oil dilution setup, where you add gasoline to the oil pan at shutdown, to lessen the drag for cold starting.

A buddy who lives in Alaska has this on his C185.

I think it was Elmer Fudd who said "very carefully".

All the big radials had provisions for oil dilution and charts for amounts of fuel to add and boil off times. In cold weather, boil off times are considerable. Big advantage here to liquid cooled engines with 0W or 5W oils.

This is where modern technology offers a huge leap in real world useage. Just start it up with no preheat, get your oil temps in the green (thermostat) and take off.

[Bill Dicus]

Originally Posted by akschu

Absolutely it is. The loose lycoming is designed to have proper piston/bore clearances when it is hot, therefore when it is cold it has very tight piston/bore clearances. The subaru engine also has tight piston/bore clearances, but not nearly as much because it has a much smaller bore and because it's not designed to operate over 250*. The bore size and temp delta force the lycoming to run much larger tolerances.



A pre heater is somewhat effective at getting the engine warm, but as soon as you start it the cold air will take the heat way pretty quick and the engine doesn't generate enough heat at idle to really warm it up. Any which way you look at it, you are expecting a cold air cooled engine to make rated HP at take-off even though the cylinders haven't grown enough to have the piston/bore clearances of running temps. The subaru on the other hand can be warmed up by a freeze plug and pan heater which is a simple plug in, then when you start it, it will come up to operating temp before take-off regardless of outside temp.

Perhaps you have never flown in -10F before, air cooled engines are a totally different animal, while a liquid cooled engine will act exactly the same except for the freeze plug heater to warm it up, not to mention the cab will break 30F.

schu

Interesting. I flew a Commanche 260 with Lycoming IO-540 for many years. Originally it had no Tanis and we rarely used pre-heat due to availability and cost issues. The engine was started many many times below zero F. We didn't fly until we had an oil temp indication. Our engine was overhauled at 2200 hours. Everything in the engine met field overhaul tolerances except for the crank and cam bearing shells. If cold starts are that terrible how did our engine do so well? Bill

[SvingenB]

Originally Posted by rv6ejguy

My record starting an engine here without being plugged in is -38C. I don't think a Lycoming would do that.

A typical 550 watt block heater will raise coolant temps from -20C to +10C in about 1 hour- pretty efficient.

I have never run my car in -38C, but I remember once it was -32 or something. The main problem at those temps is that the engine will not heat up properly unless air to the radiator(s) and engine is blocked off (usually done in the middle of nowhere with cardboard, aluminum foil or whatever you can find while freezing your fingers off ) The heating of the cabin air alone, is more than enough cooling at those temps.

The problem is much more severe for modern diesel engines, especially the larger ones. If it gets just below 0C, the engine will start to cool down. Here (in Norway), diesel cars from 2L displacements or thereabout usually have mounted an additional heater (Webasto), that burns diesel and heat the cooling water during the whole ride if needed.

You can purchase kits consisting of baffles that block off some of the air flow at the intake for Cessnas. I think Cessna makes the kits themselves.

[rv6ejguy]

We had nearly 2 weeks here where the OAT was never over -20C and was down to -36C for a day or two at night. I was driving my trusty 1984 Toyota Supra winter beater with our SDS engine management system on it.

Brutal on the the wheel bearings. You let the clutch out at idle and the engine almost stops due to the congealed trans oil. The shocks and rubber bushings are virtually solid and it rides like a horse buggy. But start it does. Takes about 5km of slow driving to get coolant up to 50C to get a bit of heat and a full 10-12 km to get the thermostat to open at 80C and full cabin heat. Didn't need cardboard over the rad but in the old days when I drove 1200 Corollas with the heater on full blast, the coolant temp would fall to about 60C at idle.

[akschu]

Originally Posted by Bill Dicus

Interesting. I flew a Commanche 260 with Lycoming IO-540 for many years. Originally it had no Tanis and we rarely used pre-heat due to availability and cost issues. The engine was started many many times below zero F. We didn't fly until we had an oil temp indication. Our engine was overhauled at 2200 hours. Everything in the engine met field overhaul tolerances except for the crank and cam bearing shells. If cold starts are that terrible how did our engine do so well? Bill

I'm not sure about your conditions, but I suspect you didn't regularly fly in below 0 F weather. In my current ride (C-150) I only see a small oil temp indication even after a 5 minute climb.

I'm happy to hear that your engine went that long, that is great.

My record for starting my diesel truck without the block heater was -38F (-39C) and no it never warmed up.

My wifes van has been started in that cold, and if you wait 10 minutes it's at operating temp, something I have yet to see with my aircraft engine at -10F even after hours of use.

schu

[Mike S]

Originally Posted by akschu

My wifes van has been started in that cold, and if you wait 10 minutes it's at operating temp, something I have yet to see with my aircraft engine at -10F even after hours of use.

schu

One of these cooling systems has a thermostat controlling the flow of the primary cooling medium.

Anybody care to guess which one????

P.S., pass the popcorn.

[N395V]

[quote=

P.S., pass the popcorn.[/QUOTE]


I doubt this thread will be that exciting. I think he now realizes that if he posts anything that is less than constructive he will be permanently banned from the forums. So save the popcorn.