Improving fuel economy for the 1991 200q 20v

Enzeder enzeder at
Fri Mar 11 05:22:23 EST 2005

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 800hp 
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 velocity.
>>(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 is 
>>>proportional to the cube of velocity (the power to overcome drag 
>>>anyway), cruising at 60 mph will likely get you better fuel economy than 
>>>cruising at 80 mph.

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