On Wed, 03 Feb 2010 11:28:14 -0000, Willy Eckerslyke
wrote:

Dave Plowman (News) wrote:

If you made two engines identical - apart from one having ally block
and head while the other cast iron - which would warm up fastest after
a cold start?

Aluminium is a better conductor of heat, so presumably the coolant
used for the ally block would would warm up quicker. But if they were
air-cooled engines, heat would be lost quicker to the air from the
ally block.

http://www.engineeringtoolbox.com/th...als-d_858.html
Water cooled. My experience of ally engines says they are slower to
warm
up. Of course newer ones will have a much lower water content than older
designs and many newer designs use some if not all ally. Hence the
theoretical question.

I suppose there could still be a large degree of air cooling going on,
even with a water cooled engine. So even if heat is conducted quicker
into the coolant, this is balanced by more heat being lost to the air.
Or something...

Thermall Capacity of iron's .46 KJ/kg, thermal capacity of aluminium is
..91, but engine blocks tend to be similar volumes rather than weights and
allys a1/3 of the density. But given ally's 3 times as conductive I
suspect the whole engine warms up evenly, in a cast iron engine the
coolants heated in the head faster than the block warms up.

--
Duncan Wood