On Friday, 28 February 2020 08:07:51 UTC, 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.

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.

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.

Tim

MPG has gone from, depends hugely on car & year, but typically 20s & 30s all the way upto 90mpg, depending what you get. So efficiency covers the range there of around 4:1. That means a lot less exhaust heat - but the heat going into the engine block is much the same in each case. Improving efficiency doesn't change that, and that's what powers interior heating on all modern ICE cars.

More effective cost cutting means a smaller interior heater matrix, which won't give enough heat output until the engine is hotter than otherwise. Contrast that with the original Lada that was specced to provide a +20C cabin at -40C outdoor temp - an important survival feature in Siberia. For UK use it was overkill, but it did mean it heated up fast.


NT