T3 Recirculating Heat

[Greg Merritt <gmerritt@Chem.LSA.umich.edu>]

Hi all,

	I have been conducting a bit of a heater experiment with my '71 
squareback.  The mean temperature here in Michigan in January is about
22F/-5C, so we need all of the help we can get.  Add to that the fact that
one of the DPOs (Dreaded Previous Owners) removed the thermostat and
pre-heat flaps, and it's frozen toes all around in my square.

	So!  I used a heater blower fan from a '72+ Type II/IV to turn my
heater into a recirculating system.  Instead of drawing in cold air from
outside of the car to send through the heat exchangers, it is a
(relatively;) closed system that sends cabin air through the exchangers
again & again.

	One of the biggest negatives with a recirculating system in an
air-cooled VW is that you typically have to cut the firewall somewhere. 
(It's called a FIREwall for a reason, remember!)  I have a spare, ratty
engine cover, so I put the hole in the spare cover. 
 
	Now, the blower is a squirrel-cage turbine with two exit ports.  I
mounted it toward the right side of the rear of the engine compartment,
with its intake flush against the decklid when closed.  It's sealed
against the decklid opening with closed cell weatherstripping.  I've
capped off the fresh air outputs on the stock fan housing (plastic spray
paint can tops w/ hose clamps!  Works great!), and have run the outputs of
the electric fan to the heat exchangers with heater hose. 

	To prevent crud in my cargo area from falling directly into the
fan, I got some large diameter pvc pipe--a flanged mount, a 90deg elbow,
and a drain cover--so that the intake hole is vertical, not horizontal;
stuff can't fall in.  It looks kind of like a periscope there in the back.
:)  Since my rear window defogger doesn't work, I redirected the defogger
wiring to the fan.  This way it uses the defogger's dash-mounted switch
and the defogger's relay under the back seat.  Also, I can still just pop
off the engine cover any time.

	Now... how well does it work, you ask?  The jury is still out.  It
seems to depend upon what kind of driving you're doing.  The blower puts
out more air than the stock setup at idle, but it's less flow than, say,
3rd gear at 45mph with the stock setup.  For around town, with a large
fraction of time spent sitting at stop lights, this setup is a big
advantage.  For a long highway cruise, the stock setup might heat up more
quickly.  I say "might."  I'm not sure how it will do when it's *really*
cold, like 5F(-15C) or -10F(-23C).  I'm hoping that the recirc will do
lots better, considering that the stock setup continuously blows cold,
cold, cold outside air over the exchangers. 

	For kicks, I might mix up the system--connect one side to the
stock setup, one side to the fan.  Not 100% clear to me how all of the
advantages & disadvantages will pan out, but I might try it to find out.

	...and while I'm on the subject of cold, my wonderful squareback
starts first time when cold--even -10F!  The fuel injection is wonderful!
Also... I filled the transaxle with Redline synthetic oil.  It's supposed
to do much better at low temps.  I will report to the list on how well
this works when it gets *really* cold.

-Greg (brrrr!)
'71 squareback
'63 Beetle