Why does brake efficiency increase with load when there is no throttle to introduce pumping losses proportional to load?

Why does the amount of power lost to coolant decrease as load is increased?

Any input or help would be very much appreciated!

Adam

Also why are diesels so bloody noisy when cold ??

not sure exactly, but there farrr superior to petrol engines IMO of course

Normaly aspirated or turbocharged ?

Diesel "knock" is louder when cold because it's the sound of the cold diesel oil travelling through the injector, as it warms up it becomes thinner and therefore quieter.

quote:

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Originally posted by martthefridgeman
Normaly aspirated or turbocharged ?

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" Diesel "knock" is louder when cold because it's the sound of the cold diesel oil travelling through the injector, as it warms up it becomes thinner and therefore quieter"

plausible, but sureley incorrect, as the diesel no mater what temperature the engine is, will still arrive at the injector cold

I thought it had something to do with the glow plugs pre-igniting the mixture. Definitely something about the timing of the burn IIRC - maybe the burn is retarded when it is cold?

[Edited on 6-12-10 by RazMan]

The diesel works by pressurising air without the presence of fuel, only injecting it just before peak pressure and temperature is reached. The peak temperatures will be lower when the engine is cold so I can only presume that will cause later combustion of fuel, resulting in a more prominent knock, possibly from the resulting natural retardation of combustion!