Date:         Wed, 9 Oct 2002 11:16:21 -0700
Reply-To:     Randy Bergum <organslave@EARTHLINK.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Randy Bergum <organslave@EARTHLINK.NET>
Subject:      Re: best speed for best gas mileage
Comments: To: Dennis Haynes <dhaynes@OPTONLINE.NET>
Content-type: text/plain; charset=US-ASCII

The tire drag is roughly equal to the air drag at about 31 mph.
Figger 10 lbs drag per thousand of weight on the tires, which remains
fairly independent of speed.
Air drag is:  F=(1/2*Rho*V^2)*Cd*A
        Where F = Force of Drag in pounds
                Rho = Air density (Pounds per cubic foot)
                V = Velocity in Feet per second
                Cd = Coefficient of Drag (unitless)
                A = Frontal Area (Square Feet)

        Rho is about .00238 Lb/Ft^3
        Cd = .44 (This can vary a little with speed and accessories)
        A = 35 square feet (rough guess)

You could streamline the van and increase mileage, but there's still the
tire drag.  Best mileage occurs with zero weight, and zero air drag, with
fast speed.

Things could be done to reduce drag on our vans, but most prove to be
unusable in everyday driving.


Randy Bergum
1990 Carat


> [Original Message]
> From: Dennis Haynes <dhaynes@OPTONLINE.NET>
> To: <vanagon@GERRY.VANAGON.COM>
 > Date: 10/8/2002 7:53:36 PM
> Subject: Re: best speed for best gas mileage
>
> The losses at speed are due mostly to wind resistance, not friction.
>
> Dennis
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
> Of G.M.Bulley
> Sent: Monday, October 07, 2002 10:03 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: best speed for best gas mileage
>
>
> 35 mph in 4th on flat ground. Encounter a hill? Go to 3rd, then second.
>
> The losses to friction above 35 rise exponentially. If I recall
> correctly above 55mph, 80% of fuel for the average car is spent
> overcoming friction.
>
> Bringing your ideas to life,
> G. Matthew Bulley
> Bulley-Hewlett
> Business: www.bulley-hewlett.com
> AIM = IExplain4u
> Phone: +1.919.658.1278
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf
> Of Dart 330
> Sent: Monday, October 07, 2002 7:16 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: best speed for best gas mileage
>
> I am curious at what highway speed my Vanagon will get the best gas
> mileage at. Would it be at the max engine torque rpm (2800 for my 1.9 I
> think)? I am planning a trip for Thanksgiving break and am considering
> slowing down from my usual 4000 rpm cruise to save gas money and enjoy
> the scenery a little more.
>
> Thanks,
> Nathan
> 85 Westy
>
>
> _________________________________________________