engine running lean means it is running hot??

Greetings.

Why does an engine with lean carburetion tend to run hotter than an
engine with normal or rich carburetion?

thanks!!

"t" > wrote in message
ups.com...
> Greetings.
>
> Why does an engine with lean carburetion tend to run hotter than an
> engine with normal or rich carburetion?

Lean == greater air-to-fuel ratio than rich. More air means hotter. Have you
ever used a cutting torch? Same principle. A super-lean mixture can melt a
hole in a piston.

On 17 Apr 2005 07:37:25 -0700, "t" > wrote:

>Greetings.
>
>Why does an engine with lean carburetion tend to run hotter than an
>engine with normal or rich carburetion?
>
>thanks!!


Amongst many things that are involved in this, combustion by-product
helps to carry away heat through the exhaust. This by-product of
combustion (which is very different when the fuel/air mixture is not
correct) is mostly water vapor by this time in the combustion
p[rocess. Usually it is only a tiny bit but it makes a difference.
This is probably one of the most "missed" items in discussion of
cooling a cylinder............timing is not everything, but can help
make up for some of this, either in valve or ignition timing, on most
*watercooled*, carburetted engines. Be careful how you apply it to
ACVW's.

Also as JS stated the heat of the burn inside the cylinder is higher
when the fuel air mixture has less fuel and more air.........this only
to a certain point , as there is a point where the fuel air mixture is
too lean to iginite under the given conditions in your cylinder/s. It
is a common occurence though.

The funny thing about this is, in most carburetted *watercooled*
engines, you can run higher octane fuels and advance the timing and
get better gas mileage. Or if you like you can lean down the mixture a
bit and get a bit more pep.

If you do this in your ACVW, you will burn a hole in the #3 piston
face post haste. This is due to cooling issues and the hotter/faster
flame front. The valve for exhaust on #3 will not be open long enough
to allow the heat produced to be pushed/sucked/absorbed from the
cylinder. The temp of the flame front, the burn rate of the fuel air
mixture, .................all of this and more will cause you issues
on the bug engine. Whereas if it were any other engine with carb and
*watercooling*, there is a much wider range of abusability or as some
may call it a margin of error.

I am sure I am not covering all of the things that are involved, so i
left it open for further discussion. Many items will be involved and A
thourough understanding of the combustion process is needed to make
decisions on fuel/air mixture adjustment, ignition timing, valve
timing, porting, etc......................LOL

Sorry if this is too much, but it is really, like I said before, just
a start,...........the tip of the iceberg so to speak.




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t wrote:
> Greetings.
>
> Why does an engine with lean carburetion tend to run hotter than an
> engine with normal or rich carburetion?
>
> thanks!!

Evaporation. When a liquid is converted to a gas, it removes, or carrys
away heat. When you burn fuel vapor, it creates heat, it also absorbs
heat. Less fuel vapor, less heat is absorbed. This is one of the
problems with running propane, since it's converted to a gas by the time
it gets to the combustion chamber, none of this "cooling" happens, and
you eventually burn something.
--Mike