View Single Post
Old 08-31-2011, 09:39 PM   #1 (permalink)
Cd
Ultimate Fail
 
Cd's Avatar
 
Join Date: Feb 2008
Location: Austin,Texas
Posts: 3,585
Thanks: 2,872
Thanked 1,121 Times in 679 Posts
How much fuel is wasted to bad aero design ?

For those of you good in math on this forum, I was just curious how many gallons / liters of fuel could be saved each year if auto makers simply incorporated an extra crease or two into their bodywork to bring the Cd down into the mid twenties versus the usual .31 Cd most cars have now a days.

From Wikipedia :

" According to the US Bureau of Transit Statistics for 2008 there are 255,917,664 registered passenger vehicles. Of these, 137,079,843 were classified as automobiles, while 101,234,849 were classified as "Other 2 axle, 4 tire vehicles," presumably SUVs and pick-up trucks. Yet another 6,790,882 were classified as vehicles with 2 axles and 6 tires and 2,215,856 were classified as "Truck, combination." There were approximately 7,752,926 motorcycles in the US in 2008. "

Lets say that 100,000,000 cars listed above had an average Cd of .35 and an average F.E. of 25 MPG.
Then lets compare the same cars, but this time dropping the Cd down to .25 , with the increase in fuel economy from less aerodynamic drag, how much fuel would be saved if each vehicle traveled 100,000 miles ?

How much fuel could be saved if the Cd was dropped to .25 and the F.E. brought up to 35 mpg like the proposed new regulations ?

We all know that to get good aerodynamics, the ideal car would look like an oversize roach ( example - the GM Sunraycer ), however I am continually surprised to see ordinary 'boxy' looking cars getting excellent drag numbers.
An excellent example being the recent post from lunarhighway regarding the Mercedes B class hatchback.
http://ecomodder.com/forum/showthrea...-cd-18614.html



After looking at this car from all angles, it really makes one wonder why that all the rest of the cars out there have such 'high' Cd numbers in the .31 range.

Nearly every hatchback car sold in the U.S. today has a Cd of .31 It seems to be the standard.

As a reminder of cars that are sleek, but look ordinary, the Lexus LS430 had a Cd of .25, which matches that of the first Insight and current Prius.



When I look at the design of the B class and also think back on the design of the Lexus LS430, it seems obvious to me that cars have a huge amount of freedom for designers to make cars that look exciting and different.

Just because a car is streamlined does NOT mean it has to look like every other aerodynamic car .

  Reply With Quote