Hi:

There is another factor to fuel economy besides aerodynamic drag and that's the 
rolling resistance of the tires.  Larger diameter tires have lower rolling 
resistance than smaller tires.  This is different than the coefficient of 
friction of the tire that relates cornering and the power needed to smoke the 
tires.  Under inflated tires result in wasted gas.

Gas engines have a "throttle" that creates a vacuum in the intake manifold to 
slow down the engine.  It takes horsepower to overcome that vacuum.  A diesel 
engine does not use a throttle and uses a different chemical cycle so is more 
efficient, hence their use for commercial vehicles.  The energy in a liquid 
fuel is closely related to it's density.  Maybe a measuring cup and scale are 
need to shop for fuel?

A basic computer program that uses numerical integration to determine the 1/4 
mile elapsed time and velocity is on web page: 
http://www.prc68.com/I/CSX3282.shtml#ET
Tire growth with speed is also included so the program works for AA Fuel dragsters.

The vehicle description gives an idea of the factors needed:
http://www.prc68.com/I/Images/Cob_RMB1.txt
http://www.prc68.com/I/Images/Cob_RMB2.txt < vehicle description
http://www.prc68.com/I/Images/Cob_RMB3.txt
http://www.prc68.com/I/Images/Cob_RMB4.txt
http://www.prc68.com/I/Images/Cob_RMB5.txt
http://www.prc68.com/I/Images/Cob_RMB6.txt
output
http://www.prc68.com/I/Images/Cob_RMBas.jpg
http://www.prc68.com/I/Images/Cob_RMBbs.jpg
http://www.prc68.com/I/Images/Cob_RMBcs.jpg

-- 
Have Fun,

Brooke Clarke
http://www.prc68.com

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