On 28/02/2020 08:07, Tim+ wrote:
Steve Walker wrote:

The alternators are far bigger than anything needed for an electric fan
- on my previous car, it could drive a 1kW electric heater to speed up
heating of the car, as the highly efficient diesel was too slow to warm
up in the winter!

This bit about diesels being so efficient that they are slow to heat up a
car has got to be nonsense.

Not really.

Think about it. ICEs turn fuel into heat and heat into motion. An
efficient engine turns more of that fuel into motion by generating more
heat from the same volume of fuel.

Therefore a 100 bhp petrol engine or a 100 bhp diesel are both producing a
100bhps worth of heat, its just that the diesel is burning less fuel to
produce that heat.


Er no, that is not even WRONG. A 100bhp engine idling at 2 bhp will if
its a diesel likely produce 4 bhp of heat and 2 bhp mechanical energy to
overcome friction.

If its petrol it will be well off it's efficiency curve and likely
produce nearer 20bhp of heat.

At rate output of 100bhp both will likely be producing upwards of 200bhp
of heat - 300KW or so.



As a consequence, power for power, efficiency *isnt* the reason that some
diesels are slow to warm up. Much more likely its just down to the weight
of cast iron in the engine.

That is also a factor.

And yet my latest diesel warms up much faster

And is still an iron block/Al head design.



Tim




--
In todays liberal progressive conflict-free education system, everyone
gets full Marx.