"Short Wave Sportfishing" wrote in message
...
On Mon, 23 Feb 2004 20:10:04 GMT, "Geoff 93 RRC"
wrote:

If you are looking for power and clean combustion, a hotter plug is
always the best choice

Actually, the heat range of the plug only refers to the plugs ability to
transfer heat from the plug to the head. A hot plug is one that that the
tip retains more heat, a cold plug transfers heat quickly. When driving,
the tips of the spark plugs are heated to incandescence. The heat must
travel from the tip through the shell and ultimately into the water jacket
of the cooling system. If the plug is too cold it will foul, if its too hot
you will get detonation, that is, the fuel will ignite before the timed
spark -- and you can blown a hole through the piston!

The octane rating of the fuel and compression ratio will determine the
correct heat range plug to use. Unless you have modified the engine, stick
to the manufacturers recommendation.

Rich

On Tue, 24 Feb 2004 00:00:37 GMT, "Rich" wrote:


"Short Wave Sportfishing" wrote in message
.. .
On Mon, 23 Feb 2004 20:10:04 GMT, "Geoff 93 RRC"
wrote:

If you are looking for power and clean combustion, a hotter plug is
always the best choice

Actually, the heat range of the plug only refers to the plugs ability to
transfer heat from the plug to the head. A hot plug is one that that the
tip retains more heat, a cold plug transfers heat quickly. When driving,
the tips of the spark plugs are heated to incandescence. The heat must
travel from the tip through the shell and ultimately into the water jacket
of the cooling system. If the plug is too cold it will foul, if its too hot
you will get detonation, that is, the fuel will ignite before the timed
spark -- and you can blown a hole through the piston!

It is my understanding that a "hot" plug is aimed more towards keeping
heat available to burn off deposits quicker and help with a cleaner,
quicker burn when the fuel/air mixture is ignited. 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.

Perhaps I should have said Hottest Recommended Plug?

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