APPLICATION OF POWER-TO-WEIGHT THEORY

By 460-BBF-Turbo-In-CC (from the legendary Car Craft turbo thread**)

"If you don't know where you're going, you'll probably end up somewhere else."

Let's say our project car is a typical V8 compact or intermediate that weighs ~3,200 lbs. Add in the following:

120 lbs. for a tank of fuel (Gasoline 6.2 lbs./gal.)
200 lbs. for extra safety equipment required by track rules
200 lbs. for "Driving ballast" (you)
50 lbs. for the various jetsam that accumulates in a real street car (tools, maps, lawn chairs, etc.) or maybe some actual ballast to improve weight distribution.

Now the car's tipping the scales at nearly 3,800 lbs. Now let's say that you've figured out that to humiliate some arrogant jerk in a Viper ACR or a Corvette ZR1 that you need at least 140 m.p.h. in the quarter mile to be safe.

Recall that 140 m.p.h. requires a minimum of one horsepower for every 4.67 lbs. So 3,800 divided by 4.67 = 814 h.p. Factor in an extra 15% "reserve" and the horsepower target is 936 h.p. Note that this assumes that the car goes through the timing traps at the horsepower peak. If it doesn't, you'll need a higher peak to make sure that the car is making the minimum required power at the point on the torque curve that the car's gearing causes it to reach the timing traps.

If we up the target to 150 m.p.h. (3.79 lbs per pony), then we need a minimum of 1003 h.p. Add in the 15% "fudge factor" and the PLAN target is 1153 h.p. It should be clear now that quarter mile speeds over 120 m.p.h. in a typical heavy street machine are going to require in excess of 500 h.p.

And the power requirement escalates dramatically as speeds inch upward (i.e. raising the trap target from 140 to 150 requires around 200 more h.p. in our example).