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.

"Jim Kelly" wrote in message
...
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.

You have the right idea. The spark delivered to the combustion chamber is
the same regadless of the plugs heat range. The only way to get a hotter
spark is if you use a hotter coil. And using a hotter plug than the
manufacturer recommends is can damage the engine. You will always need a
richer mixture in a cold engine, the fuel doesn't atomize as well when cold.
I installed an aftermarket programable fuel injection in my truck. It takes
30-40% more fuel for cold starts.

Rich

On Wed, 25 Feb 2004 03:48:02 GMT, "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.

Ah - well then apparently I was operating under a misunderstanding
then. Although my anecdotal experience led me to believe otherwise.

Hey, can't know every thing right?

Thanks for the lesson everybody - learn (or in this case relearn)
something everyday.

Later,

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

Basic Fishing Program:

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

On Wed, 25 Feb 2004 04:34:41 GMT, Jim Kelly wrote:

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.

I made an assumption that I shouldn't have based on anecdotal
experience with my two antique Internationals.

Learn something new everyday.

Later,

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

Basic Fishing Program:

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

Short Wave Sportfishing wrote in message . ..

It is my understanding that a "hot" plug is aimed more towards keeping
heat available to burn off deposits quicker

as in, burn the deposits off the plug itself so the plug stays clean.

and help with a cleaner,
quicker burn when the fuel/air mixture is ignited.

Once ignition has taken place, the spark is no longer a positive
influence to enhance the burn, the ball is rolling, the cat is out of
the bag, Elvis has left the building.

A dirty plug will not give a consistent spark on every compression
stroke, so poor running will result. A plug too hot will pre-ignite.
In between is a plug that stays hot enough to stay clean but cool
enough not to pre-ignite. The penalty for getting too hot a plug may
be the purchase of a new piston.

It is also my
understanding that engine manufacturers allow for a range of types of
hot to cold plugs to adjust for varying conditions like altitude,
emissions requirements and other issues.

I have adjusted plugs for hot/cold on high performance engines because
of the varying temperatures in different cylinders - all within a
range of course but all on the same engine.

That's an interesting idea. Assuming there isn't a problem of uneven
ring wear or uneven carburetion, or uneven crankcase condensate drain
(on a 2-stroke), then you may be left with a slight unevenness of head
temp from one cylinder to the next. In that context it makes perfect
sense to run a hotter plug on a cold cylinder, or vise versa, to
lessen fouling of the plug in the cold cylinder or lessen pre-ignition
in the hot cylinder. What you're doing is getting the plugs to be at
about the same temperature despite the uneven head temp.

%mod%

On 25 Feb 2004 07:39:44 -0800,
(modervador) wrote:

Short Wave Sportfishing wrote in message . ..

It is my understanding that a "hot" plug is aimed more towards keeping
heat available to burn off deposits quicker

as in, burn the deposits off the plug itself so the plug stays clean.

and help with a cleaner,
quicker burn when the fuel/air mixture is ignited.

Once ignition has taken place, the spark is no longer a positive
influence to enhance the burn, the ball is rolling, the cat is out of
the bag, Elvis has left the building.

A dirty plug will not give a consistent spark on every compression
stroke, so poor running will result. A plug too hot will pre-ignite.
In between is a plug that stays hot enough to stay clean but cool
enough not to pre-ignite. The penalty for getting too hot a plug may
be the purchase of a new piston.

It is also my
understanding that engine manufacturers allow for a range of types of
hot to cold plugs to adjust for varying conditions like altitude,
emissions requirements and other issues.

I have adjusted plugs for hot/cold on high performance engines because
of the varying temperatures in different cylinders - all within a
range of course but all on the same engine.

That's an interesting idea. Assuming there isn't a problem of uneven
ring wear or uneven carburetion, or uneven crankcase condensate drain
(on a 2-stroke), then you may be left with a slight unevenness of head
temp from one cylinder to the next. In that context it makes perfect
sense to run a hotter plug on a cold cylinder, or vise versa, to
lessen fouling of the plug in the cold cylinder or lessen pre-ignition
in the hot cylinder. What you're doing is getting the plugs to be at
about the same temperature despite the uneven head temp.

I came across this idea from talking with Chuck Etchells at a
basketball game (our kids know each other pretty well) who ran (or
maybe still does) NHRA funny cars for many years. I tried it on a 440
hemi and I gained about 10% more horse power on a dyno.

Again, it's anecdotal evidence, but it made sense to me at the time
and thinking back on it, still makes sense.

Later,

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

Basic Fishing Program:

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

Short Wave Sportfishing wrote in message . ..

On Tue, 24 Feb 2004 02:36:53 GMT, Jim Kelly wrote:

If this were true, there would be no need for a choke
on a carbed engine.

Huh?

What does choking an engine (limiting the air in the fuel mixture for
a quicker start) have to do with hot plugs?

I think he was responding to:

You
have to remember that the reason you have a thermostat is to maintain
a constant temperature on the block for expansion/contraction reasons
- not for combustion. Combustion is strictly the pervue of how hot
the spark is.

Gasoline will ignite only within a range of mixtures with air. While
the block is cold, fuel in the mixture condenses on the cold surfaces
so there is not enough fuel in vapor phase to be ignited by spark.
Thus, the choke is closed to introduce more fuel to get the mixture
right, till the engine "warms up."

So we see that one function of the thermostat is to keep the block
warm enough to eliminate fuel condensation, for purposes of
combustion. And we see that combustion is the pervue of not only how
hot the spark is, but also air/fuel mixture.

%mod%

"Short Wave Sportfishing" wrote in message
...
On Wed, 25 Feb 2004 03:48:02 GMT, "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.

Ah - well then apparently I was operating under a misunderstanding
then. Although my anecdotal experience led me to believe otherwise.

Hey, can't know every thing right?

Thanks for the lesson everybody - learn (or in this case relearn)
something everyday.

Later,

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

Basic Fishing Program:

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

And if you run a really hot plug, the plug can burn up under heavy load.
Used to race cars and used a hot plug when working on the car in the garage.
got to the track late once (more than once) and left the garage plugs in the
motor. Ran good in practice for about 10 minutes, then started missing.
When I pulled the plugs the center electrodes were mostly gone.
Bill