rusty vango

is there a formula to convert eighth racing to what the car may run in a actual quarter mile? everybody seems to think eights racing is the *****. but I beg to differ, its quite another thing to run the quarter mile.

RedLeader289

iTrader: (2)

Given the numbers it theoretically wouldn't be hard to do.

You know at the beginning of the eighth you are at 0 and at the end you know your speed and the time it took you to reach that speed.

bear with me:

take your speed as your final velocity, v.
your 1/8 time as t.
your starting speed(0mph) as v0.

v=v0+at

Solving that formula gives your acceleration. So, for instance say you ran the 1/8 in 5.8 seconds at 125 mph.

If we convert the speed to ft/s we get that 125 mph = 183.33 ft/s

solving for acceleration (using our formula above) gives us an acceleration of 31.608 ft/s/s (183.33/5.8 = 31.608)

I'll skip the rest of the details and give you the next formula you need.

t= squareroot(2L/a) where L is the length of the strip in feet and a is our acceleration that we calculated previously. t is our time in seconds.

If you input the length of the quarter mile, 1320 feet, and the acceleration, 31.608 ft/s/s and do the formula you get a quarter mile time of 9.139 sec.

That should be accurate to within a tenth of a second.

*edit* Normally there would be some more complicated stuff involved since your acceleration technically isn't "constant" in a car but given the relatively short length that you're driving it doesn't make much difference.

RedLeader289

iTrader: (2)

I hope that makes sense. It's a lot easier for me to write out on paper than to type, I'm an engineer so I kind of jumped when I saw you asking for a formula, haha.

Fast355

iTrader: (2)

From experimentation I have found 1/4 mile ET will be roughly 1.55-1.57x the 1/8 mile ET.

13TX

^^^ This