Improving fuel economy for the 1991 200q 20v
alancordeiro at comcast.net
Fri Mar 11 07:50:59 EST 2005
At 100 mph, wind drag is about 95-97% of the total losses.
so your approximations are correct.
(in our case it runs 65 Hp to do 100 mph......)
----- Original Message -----
From: "Enzeder" <enzeder at comcast.net>
To: "Dan Cordon" <cord4530 at uidaho.edu>; "alan cordeiro"
<alancordeiro at comcast.net>
Cc: <200q20v at audifans.com>
Sent: Friday, March 11, 2005 5:22 AM
Subject: Re: Improving fuel economy for the 1991 200q 20v
> Alright - on a tangent.
> am I right to assume then that:
> If it takes 100hp to push a car through the air at 100mph, it'll take
> to push it through the air at 200mph, and 2700hp to run 300mph. (assuming
> someone was foolish enough to leave all other things equal).
> Sometime in the late 80's or early90's I remember reading about a Camaro
> (late 60's model) that crossed the finish line of the Silver State Classic
> at 211mph. It was supposed to have about 800hp and looked about as
> aerodynamic as a brick. I think it was owned by a father and son team
> named Gotleib.
> At 06:20 PM 3/5/2005, Dan Cordon wrote:
> >Good points Alan. Especially on the 'too slow' issue. I don't anticipate
> >there being much difference in fuel economy of driving 35 mph vs. 45 mph.
> >But aerodynamic loads certainly increase in the 65+mph range. And there's
> >a good chance you would have worse fuel economy if you were driving the
> >whole trip at 25 mph.
> >And you're correct on the energy too. That's a perfectly logical way to
> >look at it as well.
> >For everyone else's sake:
> >Energy = Fd * distance
> >Power = Fd * velocity
> >Alan has a great point...using energy might be more intuitive, since it's
> >looking directly at distance traveled. For a given distance, if you drive
> >it at higher power, you'll probably get there in less time - perhaps
> >confusing the comparison some.
> >Thanks for the different viewpoint.
> >alan cordeiro wrote:
> >>Energy used to overcome drag is proportional to the square of the
> >>(power used is velocity cubed...but gas used depends mostly on energy)
> >>Drag force, Fd = A + BV + CV^2
> >>and energy is Fd * distance.
> >>Unfortunately at low throttle angles the engine is running at lower
> >>volumetric efficiency, overall power conversion efficiencies run
> >>way below Carnot cycle theoretical, probably in the in the 10-15% range,
> >>so going VERY slow can also be counterproductive
> >>>You didn't mention anything about aerodynamics. At highway speeds, the
> >>>drag force is quite significant. Hard to say what would improve the
> >>>aerodynamics of our cars....but it could be improved upon. Since drag
> >>>proportional to the cube of velocity (the power to overcome drag
> >>>anyway), cruising at 60 mph will likely get you better fuel economy
> >>>cruising at 80 mph.
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