Date: Sun, 17 Oct 2004 11:53:59 -0600
Reply-To: jimt <wetwesty@TACTICAL-BUS.INFO>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: jimt <wetwesty@TACTICAL-BUS.INFO>
Subject: Re: aerodynamics, was: 101 MPH Vanagon!
In-Reply-To: <a06002009bd97cd5ec341@[218.101.117.108]>
Content-type: text/plain; charset="ISO-8859-1"
On 10/17/04 5:02 AM, "Andrew Grebneff"
<andrew.grebneff@STONEBOW.OTAGO.AC.NZ> wrote:
>> ProjectZwo had some bolt-on stuff that was supposed to help
>> Not sure if it was aerodynamic or just apperance help but anyway, a rear
>> wing, side skirts and a deeper air dam
>> But I guess the best thing to do to reduce drag would be shorter (lower)
>> coilspring, smaller mirrors and narrow rims and tyres :-)
>> And the Vanagon is not all bad, if you check Cw value and not bother about
>> front area (Cw x A) it΄s actually supposed to be better than a Jaguar E-Type
>> !
>
> The T2 bus was also better than the XKE Jag, and
> I'd bet (if anyone bothered to test one) the T1
> would be also.
>
> I have grave doubts that Projektzwo's kit has
> been anywhere near a windtunnel, likewise the
> stock airdam.
>
> Vans may be relatively aerodynamic, but they
> still have a large frontal area, which means that
> they still have to push all that air aside...
> which is why they start to gulp fuel as speed
> rises above ~100-110kmh.
>
> What Calle says about reducing that frontal area
> is correct, but with such a large vehicle the
> effect would be minimal. A roof-chop, channel and
> perhaps narrowing the van... anyone good at
> PhotoShop?
> --
> Andrew Grebneff
> Dunedin
> New Zealand
> Fossil preparator
> <andrew.grebneff@stonebow.otago.ac.nz>
> Seashell, Macintosh, VW/Toyota van nut
>
>
A while back I got in discussions with a neighbor from up the street on my
gas mileage phenom of suddenly nose diving at about 70 mph. He works for a
company that the engineers work that kind of problems. What they did was
showed me on their systems what happens with the typical semi or other flat
nosed vehicle.
Basically the equations work on squares as velocity goes up.
You start at lower speeds and little effect.
Start getting up to what the spot they had a fancy name for and suddenly
those squared number became very significant.
Basically the vanagon was going to see just the effect I was seeing. It
comes down to how much horsepower is needed to push past a resistance. Base
figure for the vanagon was about 45 horsepower (and the air cooled had a
67hp engine). At about 60 to 65 it needed 47 horsepower. At about 65 to 70
it was going to need about 52 horsepower.
Their estimation of what I would need to do was bring the bumper/nose out
about 10 inches and slope it to the sides and up. Basically putting the
flat surface of the nose at about the same angle as the windshield. That
would theoretically move that critical point of significance up about 10mph
and get my gas mileage back again. Make one vanagon into a eurovan.
Now compute this one...
Air cooled vanagon at 67hp (under 60 mph)
AC unit at 5hp
Standard run hp of 45
Through a thousand pound westy pack on 3hp
The engine that actually performs well at 90 percent or better is not a
quality of the Air cooled engines. That engine is already being pushed near
90 percent and it is only on a flat level ground with no headwind.
jimt
Planned insanity is best.
Remember that sanity is optional.
http://www.tactical-bus.info (tech info)
http://www.westydriver.com
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