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About The Calculations
The programs used are based on formulas (see the box to the right) in the "Auto Math Handbook" by John Lawlor. They were based on tests conducted by Patrick Hale, who distributed computer software called Quarter Jr which calculated 1/4 mile acceleration and took into account factors such as aerodynamics, gearing, etc. The QUARTERjr. formulas were derived empirically (via experimentation), and have been used with confidence by professional drag racers for years. 
We did our own survey and found that the calculations were a little generous in that every car was faster than it should have been. For more accuracy, the weight and horsepower data for 25 cars was entered in a spreadsheet. The numbers were crunched (eliminating the two highest and the two lowest) and averaged into a more accurate formula, which basically redefined the 5.825 factor. The front wheel drive and rear wheel drive figures, which are based on Car and Driver road tests, are available.
Why seperate formulas for front and rear wheel drive cars? In a word (two words, actually): weight transfer. When a car accelerates, the rear wheels are pushed into the ground (more weight) and the front wheels are pushed away from the ground (less weight). For rear wheel drive cars this is an advantage as the extra weight means more traction and they "hook up" better. It is also why it is so easy to chirp the front tires on a front wheel drive car, even those with low horsepower. The same phenomena can be seen at a dragstrip as the front tires immediately jump from the surface on acceleration. Play around with these calculations and you will soon discover an old racers adage: "To go faster, add lightness." Put another way, it is often easier to gain speed by taking away weight instead of adding horsepower. A rule of thumb amongst drag racers is that removing 200 lbs. will improve your 1/4 mile time by approximately .1 second. That is why when manufacturers come out with a serious racing version of a car, a weight loss program is part of the package. The WebCars! calculations do not take into account a number of factors, such as aerodynamics, gearing, elevation, transmission and many other factors. Even tire size can make a difference, as big horsepower cars will slip at the beginning, slowing down the car. Temperature, humidity and elevation affect horsepower and are also factors.
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