Date: Mon, 30 Nov 1998 11:36:33 -0600
Reply-To: Blue Eyes <lvlearn@MCI2000.COM>
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: Blue Eyes <lvlearn@MCI2000.COM>
Organization: Vexation Computer
Subject: Re: Vanagon total drag and mechanical losses
Content-type: text/plain; charset=us-ascii
I read Bob's suggestion to Martin:
"A far more reliable indicator would be just the placement of a
Vanagon in a wind tunnel, like the one down in Marietta, GA.
Interested in donating some $'s? $3000/hour, via appointment, of course."
I know you can spend $3,000 /hour for full blown wind tunnel testing. But
paying a lot for something doesn't make it better than other options. If load
testing in that wind tunnel is worth $3,000 per hour, then using my suggestion
with the tow cable is worth over $3,000 per hour because mine covers the full
running loads the motor "sees" except for transaxle losses, which are supposed
to run between 3 and 5% according to sources I've read. Wind tunnel testing
won't tell you how much power tire flexing eats. Remember those hot tires?
Brakes drag, wheel bearing impose loads. It all adds together to create the
road horsepower loads you can't avoid on the highway. The wind tunnel is a
wonderful tool. It isolates the most progressively important load for high
speed running. But it's not a good approximation for total road horsepower
requirements unless you use one with the moving belt and the tow cable. Hum,
sounds vaguely familiar. It must be better if you have to pay a lot of money
for it, right?
You can read that VW claimed the Vanagon had a .44 coefficient of drag in an
early Road & Track Vanagon Road Test which is repeated in the archives. Use
the search string, "Road Test." Granted, that wasn't a Westy, but it should
apply to most Vanagon based vehicles throughout the entire production run
because the body shape stayed about the same. Too bad it's not close to the
Vixen motohome's .30 coefficient of drag. The nice thing about dirty designs
is that improvements are usually easy to make, where as improving a Vixen's
.30 CD or the Passat's .27 CD would be really tough.
It would be very interesting to know if people's attempts at reducing Vanagon
coefficient of drag actually work. Just because something is sold with lots
of "aerodynamic improvement" claims, appears trendy, and "all the racers are
doing" it, will not impress me unless it lowers that cable towing tension. If
that $420 air dam doesn't lower the towing tension, it was a damned poor
investment. It wouldn't surprise me if those smooth contoured high top
modified Vanagons actually have lower wind drag than stockers. It also
wouldn't surprise me to learn that even the manufacturers of them don't know
because they've never bothered to test their own product's effects.
Confusion reigns, but it never pours,
John
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