At 06:28 PM 6/25/2012, Dave Mcneely wrote:
>Don, what is the disadvantage of the "hot stuff from the engine
>compartment"?  The air is going into the engine to support
>combustion, after all.  That said, my air intake is inside the
>pillar, because it is used to cool an external oil cooler.  For that
>purpose, I can see why cooler air is advantageous, but not if there
>is no oil cooler involved.  mcneely

All Vanagons as they come from the factory take intake air from the
right-side pillar vent.  Syncros have a snorkel arrangement that
allows them to ford streams, but all of them have the intake closed
off from the engine compartment, either by a cardboard partition on
the 1.9l or a plastic one on the 2.1l.  All automobiles make some
effort to obtain intake air from the outside.

Reason is that at, for example, 14.7 psi air pressure (29.92 in. Hg
not corrected for altitude) 70*F air is 20% denser than 140*F air and
will thus make it possible for an engine at a given rpm to deliver
20% more power.

If you want to play with numbers for temp and altitude, there's a
nice calculator here:
http://www.stealth316.com/2-air-fuel-flow.htm   Rule of thumb is you
lose one inch of Hg for every thousand feet of altitude.

Yours,
David