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Re: Warm air

>From: Steven Ayres <comwest@well.com>

>Peter Parker=> I've been wondering about that tin box with the weighted 
>=> flap ever since I got my car. ... Why would you want to add warm air 
>=> to your motor in the summer?  ... What kind of problems are there 
>=> since I'm missing the warm air hose? 
>I'd like to hear Jim Adney's view on this, since I really can't say with 
>any authority. I speculate as you did, that the mixer raises air 
>pressure slightly at higher RPM, making it a little easier for the 
>engine to breathe. Better breathing makes the engine run cooler even if 
>the air is warm, I spoze, since the heated air will always be cooler 
>than head temperatures. Maybe warmer air helps atomize the fuel or flows 
>better through the oil bath?

Typically, this kind of air intake serves two functions.  The warmer air 
discourages carburetor icing, and the pressure drop across the flap creates 
a partial vacuum which scavenges crankcase gases from the engine in cold 
This latter requires that there be a breather hose into the air cleaner.

Im warm weather neither function is important, so the flaps usually are 
arranged so they can be hooked out of the way until fall.  Since this 
requires some user intervention, it was discontinued in the later cars, so 
FI 69s have the little counterweighted flap that does its job, but doesn't 
interfere too much with air flow.

       Melissa Kepner                                    Jim Adney
       jadney@vwtype3.org               jradney@njackn.com
                             Laura Kepner-Adney
                             Madison, Wisconsin

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