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engine preheating

improvement over engine block heaters
  (+4, -2)
(+4, -2)
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Here in Canada and in colder latitudes around the world, vehicles have engine block heaters, which plug into wall sockets (110v in Canada and USA). I don't have wattage figures in front of me, but I think they range from about 400w and upwards. Larger trucks might have 1500w units, and possibly more than one. Block heaters are water heating elements which heat the engine coolant and, thereby, the engine itself, so that the engine will start, or start better, which also prolongs engine life. During very cold weather they can be essential and on diesels they can be essential in any weather below 25F or so. They're often used at least several hours before starting a vehicle in the morning.

They're often used with timers (though many people just plug them in all night and even all day) which reduces the amount of electricity used. However, block heaters are very inefficient. They're heating metal surrounded by cold air, so much of the heat just dissipates into the air. If the vehicle is outside and it's windy, the effect is worse. On average, I wouldn't be surprised if they're 90%+ inefficient. So, they waste a lot of energy and tens of millions, maybe hundreds of millions, of vehicles have them.

There's likely no good way to insulate the engines they're heating, so how to make things more efficient? My idea is that vehicle owners have a small, well-insulated tank on wheels which they can easily move around by hand. It contains several (or more) gallons of engine coolant, a heating element, a thermostat and a pump. They keep this unit plugged in, as necessary, to heat up the coolant and the thermostat prevents it from using more power than it needs to reach a set temperature (ie: 200F). Then, when ready to start vehicle, two hoses are joined to the engine with quick-couplers and a pump injects the hot liquid into the engine, while the cold liquid in the engine flows out to the tank. The coolant is circulated, basically. This should only take a minute. The result should be a warmed engine, using a small fraction of the energy that a block heater would use.

lightning, Mar 14 2011

Baked. http://en.wikipedia.org/wiki/Block_heater
"Some cars, such as the second generation Toyota Prius, pump hot coolant from the cooling system into a 3 litre insulated thermos-style reservoir at shutdown, where it stays warm for up to 3 days" [AntiQuark, Mar 17 2011]


       It might make more sense just to have a much higher wattage heater that's active only for a few minutes, thus minimising losses.
8th of 7, Mar 14 2011

       In Siberia, they just light bonfires beneath the sump, or preferably leave the engine running all winter.
pocmloc, Mar 14 2011

       //This should only take a minute// ...before cracking the engine block.   

       Please give this idea a bit more descriptive name... the idea you have proposed is definitely not a "vehicle".   

       <edit>Thank you. Now, as [FlyingToaster] will say later, a fixup of the category will have you all straightened around.</edit>
lurch, Mar 14 2011

       At the "edit idea" screen, which is what you're looking at if you're signed in, as well as on the original "add idea" screen, there's a drop-down list to help you find the appropriate category. I'm guessing "Block Heater Improvement" is the Title you intended, however it is suggested to use a bit of imagination there as well.   

       re: the idea... I can see a possible application for a fleet of buses: replace the coolant in one, then go to the next while the stuff in the tank is being heated.   

       However for personal vehicles... dunno 'bout you, but there's no way I'm gonna mess with a -40 liquid unless I'm wearing protective gear: all in all too much hassle.
FlyingToaster, Mar 14 2011

       The purpose of the heater is to warm the cylinders and head, which in turn warms up the air you're trying to light fuel in (or rather doesn't cool it down as you compress it). There are obviously other positives to this system, but they are secondary.   

       Unfortunately I don't think there's much to gain from injecting warm coolant into the system just before starting, as the block and head will simply absorb the stored heat without really warming up.   

       For the people using the timers it may be useful to have some kind of well insulated 'hot coolant' store in the vehicle from the last time it was run to cut a few minutes off the start of the warming cycle.
Skrewloose, Mar 15 2011

       My responses.   

       1) Yes, an onboard system is possible, too.   

       2) The purpose of the heater is to allow you to start your vehicle, whereas you often can't otherwise (here). Also, to expand on prolonged engine life... I mean it reduces engine wear greatly. A big problem in any cold region, cuz oil thickens a great deal in very cold weather and so there is some damage during the first few minutes of running your engine when the oil is not where it should be. My buddy says my idea should be paired with an oil pre-pressurizing system, which apparently would also GREATLY extend engine life (in any climate).   

       3) I don't see working with cold liquid as a big problem. It just requires a good system with reliable couplers. I envision couplers like those used for compressed air - pop on/off, self sealing, etc. But there can be appropriate shielding of the coupler area, etc, too.   

       4) Higher voltage block heaters... Multiple ones would probably make much more sense, but you'd be sucking much more juice and still need half an hour or so for the heat to spread, I think. Some savings, I suppose, but then people have to run multiple cords to vehicles, which may have to be on multiple breakers for larger engines.   

       5) The engine block cracking... I'll have to get back to you. Perhaps a slower introduction of the hot liquid is needed, or a larger amount of liquid at a lower temperature... I'll do some research...   

       What I see in our global future is a greater and greater need for conservation of energy. There are massive gains to be had in this particular area, but I'll think about viability of my idea some more. Thanks for feedback!
lightning, Mar 15 2011

       I our future we'll all be driving bloody golf-carts anyway.   

       I'm sure this has been discussed elsewhere, but why is it not possible to insulate an engine. Half a ton of hot metal ought not to get so cold overnight. There must be a sufficiently heat-tolerant poyurethane-type foam which the engine could be jacketed in, like the insulation on a domestic hot-water tank (but maybe only half-a-ninch thick - enough probably). Either it would be a preformed sectional moulding which could be removed and replaced for servicing, or a spray-on layer which would be broken off for servicing and reapplied.   

       Ah, I hear you say, but then the engine will overheat when running! Poppycock, I reply - the coolant system and radiator carry away most of the surplus heat when running.
MaxwellBuchanan, Mar 15 2011

       I wouldn't mind seeing that either (engine insulation): it'll come in handy when everybody's driving stop/start cycle'd golf carts, but I don't think it's gonna do much good vs. 12hrs sitting in the driveway at subzero temperatures.   

       [lightning] I just think if you're going to be bulk-transferring litres and litres of anything once a day, the application would be more favorable to usage in a bulk situation, ie: transit bus fleet waking up in the morning.   

       Otherwise what's the difference between this and having, not a regular block heater, but one integrated with the coolant pump, to both warm and circulate the liquid, without the need for adding more fluid.   

       If you're interested in pre-oiling, there's a neat system that combines it with a bypass filter as well (gives better filtration).   

       Still waiting for a Category other than "other: general" :)
FlyingToaster, Mar 15 2011

       //but I don't think it's gonna do much good vs. 12hrs sitting in the driveway at subzero temperatures//   

       I disagree. According to my calculations, a 200lb mostly- steel engine starting at 70°C, insulated by 0.5 inches of polyurethane foam, and sitting in still air (inside the engine bay) at -20°C will take over 14 hours to cool to 0°C.
MaxwellBuchanan, Mar 15 2011

       ... 'k, that's better than my lack-of-envelope calculation which included necessary gaps in the coverage... so why isn't it done ? (apart from extra cooling energy requirements during operation).   

       Note of course that you'd be hard pressed to find an all steel engine, and 10-15% of the surface area of the engine would need be exposed.
FlyingToaster, Mar 16 2011

       //why isn't it done ?// Why is a hotplate, rather than a vacuum flask used to keep coffee warm?
mouseposture, Mar 16 2011

       Circulating heaters that heat the coolant instead of the block exist and are probably less hassle.   

       On higher power, based on personal experience, that works fine for one person's vehicle in his personal spot. For large groups of vehicles (for example the company parking lot) what often happens there is the high power heaters in bulk cause the circuit to overload, the breaker to trip and no one gets the benefit of the engine heater.
NoOneYouKnow, Mar 17 2011

       //you'd be hard pressed to find an all steel engine,//   

       Sure, but all metals are roughly the same in this respect. And voids in the structure tend to do as much good (by slowing internal heat transfer) as they do harm (by having no heat capacity).   

       Actually, [lightning] you could do a simple and interesting experiment. When you leave your car for the night, take an old duvet or two and wrap the engine as snugly as you can (which won't be very snugly, obviously), and see if it's appreciably warmer in the morning than it would otherwise have been. I bet you it will be.
MaxwellBuchanan, Mar 17 2011

       Electricity is too cheap! The cost of the added hardware would far exceed the savings in electricity.   

       EDIT: also, baked (see link).
AntiQuark, Mar 17 2011

       //cracking block//
Sudden cooling of a hot head will crack it.
However, I don't think sudden heating will crack it.
Ling, Mar 18 2011

       If it's so cold you're having a hard time starting it, I think there'd be a pretty hefty thermal shock. I don't know if it would crack - I'd gladly try it out on someone else's engine.
lurch, Mar 18 2011

       //pump hot coolant from the cooling system into a 3 litre insulated thermos-style reservoir at shutdown, where it stays warm for up to 3 days//   

       ...with an reverse osmosis filter you could take out the glycol and have a nice cup of tea while you're starting the car.
not_morrison_rm, Mar 18 2011

       I seem to recall that some vehicles have louvers in front of the radiator, which automatically close when the engine compartment's temperature is below some limit.   

       In a vehicle which has this feature, the engine compartment is sufficiently close to airtight that a block heater isn't particularly inefficient.
goldbb, Mar 20 2011

       Single use thermite charges. Defrost and go...
saedi, Mar 22 2011

       Sure, thermite would heat an engine block--it would heat a hole right through the cylinder head and all the way down to the oil pan. Then it would heat the ground underneath. Or is that what you meant by 'single-use?'   

       I live in Maine, which is very nearly almost Canada, and I own and operate a 6x6 army truck as a field repair rig for my welding business. It has a massive straight-6 that is a real bear to turn over in the winter, but if I throw an electric blanket over the block (not the radiator!) and a couple of mover's blankets over that, after 2-3 hours it cranks over like it's the middle of July. This method has worked even in -10 degree (F) weather.   

       Lightning, I like your idea, but it seems overly complicated, given that the block is what needs heating, not the coolant, and as others have pointed out, introducing very hot liquid to very cold metal rarely works in anyone's favor. Perhaps instead of my ratty old electric blanket, one that contains a network of tubing through which we pump your efficiently-heated liquid?   

       On a similar note, anyone trying my method should be aware that the electric blanket _must_ be removed prior to starting the engine. Energized electrical devices and serpentine belts do not play well together. (and no, I do not source this on personal experience. It is merely an assumption.)
Alterother, Apr 04 2011

       Perhaps in such a large engine, fitting a heating element to the oil pan would work. If that's nice and warm, it'd be less goopy and easier to start. With the side effect of warming the block above it.   

       With sufficient power, it might even set the oil alight and warm the block that way.
saedi, Apr 05 2011

       Heating the oil is only one issue, usually acheived by circulation through a warming engine. The real thing to look at here is the most efficient way to heat large pieces of steel or iron (or aluminum, but not many heavy trucks have aluminum blocks) without putting undue strain on the metal. These things are designed to withstand repeated expansion/contraction cycles with specific rates; there's always a wide margin for environmental factors, but when you start monkeying around with that, sometimes monkey go too far...
Alterother, Apr 15 2011


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