Fun Stuff > CHATTER
This even more just in - the weather thread
Aziraphale:
I'm more used to seeing glow plugs on diesels. Don't remember ever seeing one on anything gasoline-powered... though it'd come in handy with the weather we've been having lately.
bhtooefr:
So, glow plugs are a different technology, for increasing combustion chamber temperatures enough to get fuel to ignite while an engine is cold. I forget the details of how they work in nitromethane model engines, but in diesels, the fuel is injected when combustion is expected to start, and normal operation uses the heat of compression to ignite the fuel. The glow plugs are used before startup and (on some engines) during warmup.
In a gasoline engine, fuel is often injected when the intake valves are open. You do not want a hot exposed surface designed to help fuel ignite in there, without any control of the ignition timing. Spark plugs are used to achieve controlled ignition, in that case (and gasoline engines are set up to not perform any compression ignition, only using the spark plugs to ignite the fuel).
pwhodges:
Unwanted compression ignition that sometimes occurs in petrol engines is what's known as "knocking", and is very bad both for performance and for the mechanics of the engine.
Akima:
--- Quote from: bhtooefr on 19 Feb 2015, 16:05 ---So, glow plugs are a different technology, for increasing combustion chamber temperatures enough to get fuel to ignite while an engine is cold.
--- End quote ---
Yes, sorry I wasn't clearer. Glow-plugs in diesel engines are used to pre-heat the head of a cold engine to get it warm enough for the diesel fuel to ignite. Many modern diesels do not require them, because of improved fuel-injection technology.
A sump/block heater is a different thing. It is intended to keep the engine slightly warm while it is parked, so that it starts more easily, and comes up to normal operating-temperature more quickly, which reduces engine wear and fuel consumption. PWH was referring to the old kerosine-fuelled heaters, which were usually flat "wick" lamps with a wire gauze guard, designed to be placed on the ground under the engine. I've never seen one, but my father has described the ones they used in the army. A home-brewed way of doing the same thing is rig a lamp with an incandescent light-bulb on a piece of wood, slide that under the engine, and plug the lead into a normal power-socket. Much better is a properly installed electric sump/block heater, but again you have to hook it up to an electric power-supply in your garage, car-port or whatever.
Oh, and burning kerosine releases a lot of water-vapour. I have forgotten the exact numbers, but I think that if you burn a litre of kero, you release roughly a litre of water in the form of water-vapour, which will then condense out on cool surfaces like a car windscreen.
bhtooefr:
And then another step beyond that is systems such as Webasto or Eberspächer coolant heaters, which run on diesel (or gasoline) and heat the coolant (much faster than even the best electric block heaters).
Downside for my application is that they slowly drain the battery, which hurts things in my case due to extreme short trips. And, they're rather expensive.
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