preheating devices?

Question

why do indirect injection diesel engines require preheating devices

Answer 1

The glow plugs ate NOT what ignites the diesel, they are used to preheat the combustion chamber before a cold start to make a self ignition combustion possible. With a cold diesel engine, the compression temperature might not be high enough to ensure proper ignition of the injected diesel fuel, causing inconvenience to the driver and increased exhaust emissions. The glow plug - an electrical heating device - helps to solve this problem.

Answer 2

Ok, let's straighten this out. No, glow plugs do not ignite the fuel air mixture. On older engines the glow plug (a single one)is located in the intake manifold and heats the air before it enters the cylinder. Glow plugs are (were) also used on indirect injection engines.

Direct or indirect injection has nothing to do with where the glow plug (s) are located. With direct injection, the injector is mounted in the cylinder head and points downward toward the cylinder. When injection occurs, the fuel is finely sprayed at high pressure (2,400+ psi) directly into the combustion chamber where combustion begins.

I don't know if any indirect injection engines are made any more. Most were phased out in the early to mid 60's. With indirect injection, the injector is mounted horizontally in the cylinder head and on the opposite side is what's called a power cell, kind of a short, fat, hollow bolt like affair screwed into the side of the head. When injection occurs, a lower pressure (1,600-1,800 psi) stream of fuel is injected, ignition begins, the still burning stream of fuel hits the concave shaped power cell and is directed back into the combustion chamber.

Direct injection engines start easier and are more fuel effecient but are noiser than indirect injection. In addition, the higher pressure direct injection pumps are more expensive to build and are noiser when in operation. A lot of the noise from a diesel is actually from the pump. Most pre-1960 diesel engines are indirect injection and post 1960 direct.

Answer 3

because it makes them easier to start in cold weather,other wise they don't turn over so well,nor do they start good,by preheating the coolant in them,this makes the engine turn over a lot better,and will make them start a lot better,the glow plugs are also considered to be a heating device,without them it would be really hard to get any diesel engine started,good luck.

Answer 4

The glow plugs are what ignite the diesel. Once ignition takes place the heat of the ignition keeps the glow-plugs hot for the next power stroke of the piston. The very first time the engine is started the glow plugs are cold, so there's nothing to get the process started. That's why you must use a pre-heater to get the glow plugs hot in the first place.