| Understanding Acceleration
As you read this article, it should become obvious that what makes a
car accelerate is simply how much torque you can apply to the rear axle
versus the vehicle weight. The terms "hp/weight ratios" and "hp/liter"
may be part of the hype in selling cars and engines but they have very
little meaning. We'll discuss hp later but for now, let's focus on torque.
In my mind, if a picture is worth a thousand words, a graph is worth
ten thousand. Study the graph below to predict how fast a car will accelerate
in the quarter mile. The numbers on the vertical scale are a measure
of how many pounds of vehicle weight you have per foot pounds of torque
to the rear axles. The horizontal scale is the quarter mile speed (mph)
and elapse time (seconds).
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