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Drag racing conversion
Over the quarter mile (about 400 metres) the time (ET) and the speed at the finish (trap speed) go together, and together with the weight they say a lot about the power. Enter your ET and the vehicle weight, and we convert to trap speed and give a rough power estimate.
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Trap speed
197,9 km/h
Trap speed and power are based on empirical rules of thumb (ET times speed about 1353, power from speed and weight). Real figures depend on traction, aerodynamics and air density.
How the calculation works
Over the quarter mile the time and the speed at the finish follow a known relationship. The rule of thumb says ET times trap speed is around 1353, so the trap speed in mph is roughly 1353 divided by ET. The same constant solved the other way gives ET from a known trap speed. We show the speed in both km/h and mph.
Power is estimated from trap speed and weight with a variant of Roger Huntington's formula, where speed is proportional to the cube root of power divided by weight. Solved for power it becomes weight times trap speed divided by 234, cubed. The constants 1353 and 234 are empirical rules of thumb, so the result is an estimate, not a measurement.
Example
An ET of 11,0 seconds gives a trap speed of about 123 mph (198 km/h), and with a weight of 1360 kg the power estimate lands at around 435 hp.
ET and trap speed over the quarter mile (rule of thumb ET × speed ≈ 1353)
| ET (s) | Trap speed (mph) | Trap speed (km/h) |
|---|---|---|
| 9,0 | 150 | 242 |
| 10,0 | 135 | 218 |
| 11,0 | 123 | 198 |
| 12,0 | 113 | 181 |
| 13,0 | 104 | 167 |
| 14,0 | 97 | 156 |
Empirical rules of thumb. Real speed and time depend on traction, aerodynamics and air density.
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