A New Performance Paradigm: The ‘Speed Per Dollar’ Index

May 31st, 2007 3:37 PM


It occurred to me that enthusiasts could use a new equation to better quantify a vehicle’s capabilities in view of its cost—something like horsepower-per-pound-per-dollar, a metric that more artfully balances power, weight, and financial outlay. Thus, the “Speed per Dollar” concept was born.

Being something of a buffoon at mathematics and graphics, I sought help to turn the idea into a meaningful standardized equation that would yield useful numbers. The staff at WINDING ROAD rallied around the concept and contacted the fine folks at Funnel Inc. (motto: “Information design that makes the complex clear”), and the concept became a reality.

The basic calculation they came up with is as follows:

(Horsepower ÷ Weight) x 10,000 ÷ Price Point x 100,000 = SpD

We think this SpD metric is uniquely useful because it weighs a vehicle’s accelerative capabilities against its cost. There’s no doubt that the Bugatti Veyron 16/4 is a tremendous technical achievement, but as a value proposition, well, it fails miserably—a development that should come as a shock to exactly no one given its plutocratic price tag.

We like the SpD because it celebrates affordable sports like the Mazdaspeed3, Chevrolet Corvette, and the Ariel Atom. It isn’t perfect (it doesn’t take into account a vehicle’s handling envelope), but nevertheless, we think it’s a better evaluation of enthusiast vehicles than existing calculations.

A few sample equations:

2007 Ford Mustang GT: (300 hp ÷ 3356 lbs.) x 10,000 ÷ $26,370 x 100,000 = 3390 SpD
2007 Lotus Elise: (190 hp ÷ 1984 lbs.) x 10,000 ÷ $42,990 x 100,000 = 2228 SpD
2007 Saleen S7 TT: (750 hp ÷ 2950 lbs.) x 10,000 ÷ $580,000 x 100,000 = 437 SpD

Check out the chart above (click on it to expand), then grab a calculator and run your own vehicle through the formula for fun-the higher the SpD, the better.