<VV> Jets for power

[NicolCS at aol.com]

Clearly, we all have a handle on this one - problem is our paradgms are all 
based on different observations! in different machines!

In my mental model, after doing useful work, the heat can go two places; the 
cooling system and/or the exhaust system AND the amount of heat involved is 
itself a variable. Whether the heat goes to the exhaust or the cooling system 
(or both) depends on a lot of things.  Ideal engine models are adiabatic, that 
is all heat goes to useful work - the exahust is minimal and the engine runs 
cool.

An effiicient engine (least amount of fuel for a given load) would logically 
have the least waste heat since more of the heat content of the fuel is going 
to useful work - this is true up to a limit.  There are limits to how lean you 
can go before thing go haywire with that theory.  Somewhere, I have a graph 
of mixture vs. temperature and the low dip was not at "max power" but quite a 
bit higher, AFIR, it is above the stoichiometric ratio. 

Here's a bit of evidince: compare the size of the radiator in a 1970 mid-size 
car with that of a modern car of equivalent weight.  The current radiator is 
about 1/2 the size and they rarely overheat.  The modern car gets roughly 
twice the fuel economy.  Slightly leaner yes, but really it's a combination of 
efficient fuel control, lower rpm, better mixing in the heads, and a little bit 
leaner average mixture.
<snip> Ned can correct me if my memory has faded (haven't flown pilot in 
command
since '69), but as I remember it, leaning the mixture at cruise raises the
EGT and probably the cylinder head temp.  Seems like that too much rise
(along with running rough) was the indication that you'd pulled the mixture
knob back too far. Roger <unsnip>