written by: Rick Ferbert
The time-slip is, for many, the only real information that is collected on a run down the quarter mile. It would be great if everyone could afford to have a data acquisition system on your car but most racers on a budget have to make do with the information on the time-slip that is provided by the track. Understanding the timing system, and knowing how to interpret and use that information is vital when testing and tuning your race car or to dial-in your bracket car.
Most timing systems provide some combination of these times for each lane: Reaction, 60, 330, 660(1/8), 1/8MPH, 1000, 1320 (¼) and ¼ MPH. Most have other indicators about the winner and MOV etc, but lets just look at your own times for now. Most racers just look at the 60, ET and MPH because these are what are talked about and understood most. Some racers may also look at the 330 or 1/8 mile times for a little more info. There is even more information there if you have a calculator or computer and are willing to do a little ciphering.
All of the timers shown on your time-slip, except reaction time, begin timing when the front tire comes out of the staging beam. The time it takes your car to move from a stopped position to out of the beam is called rollout time. When anything changes the time it takes your car to roll out of the beam, it changes when the clock starts; this changes how much of a rolling start your car has on the staging beam affecting every time from 60 to ¼ mile ETs by the same exact amount. Quicker cars vary less from staging variations than slower cars but can be as much as 0.100 sec. Even small staging or rollout variations can affect your times. These can be caused by lane-to-lane differences, staging beam differences, driver staging variations and inconsistent traction.
Since we know that rollout variations have the same effect on every timer down the track we can use split times to separate rollout differences from actual performance differences. Split times are the time from one timing position to another. For example from 60 to 660 is a split time. Simply subtract the shorter time from the longer time and you have a split time. Using split times can help eliminate some of the unknown in your time-slip since there can be no staging or rollout variation effect on the split times. Lets say for example you make a run that has the following times Run 1- Left Lane: 60=1.364, 330=3.906, 660=6.088 and 9.540 @ 140MPH. On your next run your time-slip shows Run 2 Right Lane: 60=1.380, 330=3.923, 660=6.106 and 9.560 @ 140MPH. If you calculate 60-660 split-times for each run you will get 4.724 and 4.726. There is only .002 sec. difference in 60-660 split times, yet just looking at the 60, 660 and ET you might think the variation was caused by poor traction or weather changes. The slight drop-off in split time indicates that only a small part of the overall ET change was a real performance change. There was a rollout difference between the runs either from lane variations or some other factor. When bracket racing, use split times from 60 to 660 or 60 to 1000 to prevent finish line racing from affecting your split-times. If you are testing or class racing and running out to the finish line, use the 60 to finish line split-time to eliminate staging and rollout variations for more accurate results. Using split times helps when testing jet changes, shift points and timing adjustments since these can separate the gains or losses on different parts of the track. You can calculate 60-330 time, 330-660 time and 660-1320 time. This can help show where in the run the changes helped or hurt as well as giving more repeatable results since the rollout differences are removed using split times.
Keeping your time-slips in an Excel spreadsheet on a computer can speed this calculation process up and eliminate errors.
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