This is true. As you noted, the heat carried away by the cooling system does no
work. If it were economically feasible, using materials such as ceramics, to
run higher combustion chamber temperatures, efficiency would indeed increase.

Calif Bill wrote:

"Short Wave Sportfishing" wrote in message
...
On Wed, 25 Feb 2004 02:01:22 GMT, Jim Kelly wrote:

I am questioning your assertion that "combustion is strictly the pervue
of how hot the spark is." I contend that that it is necessary to
increase the fuel to air ratio on a cold engine because the engine is not
imparting enough heat to the mix to create a combustible mix regardless
of the heat range of the plug. Therefore, engine temperature has a
direct effect on combustion.

I can agree with that. However, combustion has to be initiated by the
spark. The fact that a cylinder is operating at certain temperature
only assures that the fuel/air mix on entering the chamber is fairly
evenly dispursed. The source of ignition is still the spark. A
hotter spark means that more energy is imparted to the explosive
mixture resulting in a cleaner burn with more energy transfer. The
gas expansion rate is better because the burn is initiated quicker.

Additionally, a hotter plug in a cold normally aspirated engine means
that one can use less choke on starting. Faster start, faster warm
up.

Later,

Tom
S. Woodstock, CT
----------

Basic Fishing Program:

10 - Fish
20 - Eat
30 - Sleep
40 - Goto 10

Wrong! A hotter plug only keeps you from fouling at the temperature you are
running. No hotter spark. Same coil and ignition driving the EMF. Same
gap normally. A hotter plug, just does not transfer as much heat in the
same time as cold plug. The heat is transferred to the head and cooling
system. If you are running a cold engine, the burn is not as complete and
with a normal heat range plug, it would foul and not fire. The hotter range
plug just allows the carbon to burn off. Ideal would be a ceramic engine,
that allows you run real high temps with out melting the piston, etc. Could
get even more energy out of the gallon of gas. When starting, all the plugs
are cold. More gas as the volatility of the fuel, does not allow as much
vapor to ignite, so more fuel == more vapor. Why you get lots of carbon
(black smoke) out the tail pipe on an engine with a stuck choke.