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Diesel Tuning Fundamentals: Glow Plugs

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Glow Plugs

01.39

00:00 - Since diesel engines operate on the compression ignition principal, the heat produced during the compression stroke is essential in order to heat the fuel above the auto ignition point and begin the combustion process.
00:13 Once the engine is up to operating temperature this isn't a problem, however during cold starting and in particular at low ambient temperatures, the mass of the engine block, cylinder head and piston assembly, absorb a significant amount of the heat caused by the compression process.
00:30 To combat this and aid in cold starting, it's common for manufacturers to fit glow plugs directly into the cylinder head.
00:39 The glow plug is essentially a heating element that's powered by the vehicle's electrical system.
00:44 You could think of a glow plug as being similar to the element in a toaster or electric heater, and when powered the glow plug will glow bright orange, hence it's name.
00:54 The glow plug is located in the cylinder in such a way that the injected fuel will impinge on its surface, and this has the effect of initiating combustion, even if the engine is not hot enough for normal operation.
01:06 Once combustion is initiated the process becomes self sustaining.
01:10 So the glow plug is only required during the cold start operation, after which time it's shut off.
01:17 Due to the harsh operating conditions the glow plug is exposed to, they do have a somewhat limited life expectancy and particularly in high mileage diesel engine, replacement may be necessary.