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<DIV> Warm fuel will assist the vaporization. With care tho, to
disallow vapor lock. And most vaporization does happen in the crankcase due to
partial vacuum effect and heat there. But enough happens in the venturi to act
as refrigerant for the carb body and that can cause freezing and ice build up.
Also, the sudden expansion of the inlet air as it enters the crankcase
just past the venturi, can't be ignored either.</DIV>
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<DIV>The dynamics are complex and depend on ambient conditions but the concept
is fairly simple once the fundamental is understood: evaporation is a cooling
process</DIV>
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<DIV>MattK</DIV>
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<DIV>In a message dated 3/1/2005 8:58:16 AM Eastern Standard Time,
bob@toprudder.com writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2>e heard
of heating the fuel before it goes to the<BR>carb (on automobiles) improves
the vaporization and<BR>can increase mileage. Don't know if it is true,
but<BR>sounds plausible.<BR><BR>I believe the majority of the vaporazation in
our<BR>engines occurs in the crankcase (two strokes), not in<BR>the carb. I
also think that this process helps cool<BR>the engine internally, especially
the piston.<BR><BR>This reminds me of a problem I had with a generator
a<BR>couple of years ago. Ran fine for about 30 minutes,<BR>then would start
running erratic. Finally, I figured<BR>out it was carb ice. Click the link
below to see the<BR>quick fix for it. Ran a piece of dryer vent from
the<BR>cylinder head around to the intake. Got me through the<BR>2003 ice
storm, no power for several
days.<BR><BR>http://www.toprudder.com/photos/feb03/carb_heat.jpg<BR><BR>Bob
R.<BR><BR>--- Rcmaster199@aol.com wrote:<BR><BR>> <BR>> The action
of converting liquid fuel to a vapor in<BR>> the venturi is a part of
<BR>> the refrigeration cycle. It requires energy to do<BR>> it, which
comes from several <BR>> sources. The most important source is the
lower<BR>> than ambient pressure as the <BR>> piston drives to
compression, but ambient air and<BR>> crankcase heat contribute
<BR>> also, once the engine has reached steady state.<BR>> Insulating
the carb body <BR>> places different demands on these sources
of<BR>> vaporising energy. <BR>> <BR>> Potentially, it may
reduce air temp further which<BR>> may have a supecharging <BR>>
effect. I think you are after improved sealing<BR>> between the carb body
and the <BR>> throttle barrel, but this could be an added
benefit.<BR>> <BR>> Interesting idea Nat<BR>> <BR>>
Matt<BR>> In a message dated 2/28/2005 9:02:14 PM Eastern<BR>> Standard
Time, <BR>> natpenton@centurytel.net writes:<BR>> <BR>> The
carb is a potent refrigerator. Most carb case <BR>> heating comes from
ambient <BR>> air, not from engine case conductance. The engine <BR>>
crankcase though, should <BR>> be well ventilated. The situation may
be better<BR>> with a plastic bushing for <BR>> mounting the carb
to engine case, although I have<BR>> not done so. Nat<BR>>
<BR>> ----- Original Message ----- <BR>> From: _Dean Pappas_
(mailto:d.pappas@kodeos.com) <BR>> To: _discussion@nsrca.org_<BR>>
(mailto:discussion@nsrca.org) <BR>> Sent: Monday, February 28, 2005
1:49 PM<BR>> Subject: RE: Two Stk<BR>> <BR>> <BR>> Did you
turn down the carburettor boss to make a gap<BR>> that's filled with
<BR>> vinyl?<BR>> If not, then it's an awfully thin bit of
insulation<BR>> that provided the <BR>> desired effect.<BR>>
later,<BR>> Dean<BR>> <BR>> Dean Pappas
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