When it comes to 0-60 and qtr mile calcuations, it's very important to understand how the measurements are taken, the inherent accuracy involved, and how the measurements are used to arrive at a calculation.
Dashhawks use a vehicle's internal speedometer measurements to produce the calculations. A speedometer measurement is derived from the rotational rate of the spinning wheel under the assumption that there is no wheel slip. Since the speedometer measurement cannot make the distinction, neither can the Dashhawk. Hence, wheel spin is interpreted as translational motion (which it is not), and therefore results in a CALCULATED 0-60 and qtr mile time that is better than what is/was actually achieved. We don't doubt what you see on the dashhawk display. Rather, we doubt that the dashhawk display reflects the reality of the run.
Racelogic devices use GPS (and possibly accelerometers) to measure the motion of a vehicle. As long as the satellite signals are of sufficient clarity to produce the measurement (possibly aided by accelerometers during any breaks in signal), and are broadcast within spec, the accuracy from these devices should be very close to what is actually achieved. Furthermore, GPS signals lend themselves to post processing, which allows a post run validation of the measurements.
There are some devices that use only accelerometers. These devices depend on the precision of the accelerometers, to include the ability to zero out gravity. They would also be subject to gravity error induced by the movement of the device (e.g., if it's an IPOD), or change in slope of driving surface during the run. If you do use a device like this, make sure it can zero out gravity and keep it FIXED in position during the run.
And then, of course, there's the track where beams of light trigger timing circuits. But even these measurements come with caveats, as the type of staging (deep vs shallow) involves a roll out variable, which affects the calculated values.
2008 Redline Auto
Last edited by Bogie; 10-02-2009 at 01:20 AM.