For the first four runs, we used the out-of-the-box settings shown as "uncalibrated" in the graphs. Most of the meters can be calibrated to compensate for time gained or lost due to the vehicle's pitch. However, to do so you'll need drag-strip results to provide an accurate measure of the vehicle's actual performance. After the first four runs, we tinkered with available settings and then ran and averaged four more passes, shown as "calibrated" in the following graphs.
If the meter was capable of recording braking or lateral g, we simply used the meter in conjunction with our regular testing procedure and compared the results. As noted earlier, we made more than passes down that quarter-mile and tabulated stacks of data we also ran tests of our VBOX against the drag-strip timing system.
We did our best to boil down the data to the easily digestible graphs. If you want to see the results for every run, we've posted a spreadsheet.
Number geeks, have fun. We found the meters were off by a few tenths of a second in the worst case to a mere couple hundredths in the best case. Here, in price order, lowest to highest, is what we learned about each meter. We tested it with the drag lights, and it was more accurate than the best meter in this test, the AX Both of these systems are so close to the drag lights, however, that it's barely worth mentioning that a difference exists.
We're talking about discrepancies that are less than half a percent. However, for our testing we need real-time display of acceleration data, in-depth-analysis software, and external inputs for a brake trigger, just three of many features the VBOX has that the AX22 does not.
Judging by this current crop of performance meters, however, we find that the VBOX's advantages are being challenged. As a measuring device for a single car, most of the meters are quite good, but if you want to determine definitively whether one car outperforms another, you'd better budget some time for calibration. The VBOX requires no calibration. Before you take out your car to try to equal our times, remember that our results are adjusted for weather conditions [see "Correcting for Weather"].
We also average the best runs in two directions to cancel out the effects of wind, and we use a 3-mph rollout. And of course there is car-to-car variability. Finally, find a safe spot for testing—one that lets you concentrate on the task at hand rather than traffic.
It displays all the segment data from one drag-strip run 0 to 50, 60, 70, etc. The Passport has an adjustable distance rollout. To ensure accuracy, there is a pitch factor to calibrate the meter.
The owner's manual provides suggestions for different types of cars, and we used the correction factor of 2. After performing the four initial runs, we experimented to find a number that made the meter line up closer with the drag-strip results, which turned out to be 3. When calibrated, the Passport was a smidge less accurate than the Tazzo, but we're splitting hairs here because the difference in accuracy works out to a measly one-tenth of one percent.
The Passport has a handy skidpad function that averages the lateral g over an adjustable time period from 3 to 16 seconds. There's a calibration factor for this feature as well, and we were able to get the Passport to within 0. It's likely, however, that fiddling with the calibration factor would have reduced the discrepancy, but we're guessing that owners of these personal meters probably won't spend an excessive amount of time trying to get perfect results. As for that less expensive GT1 model, it records the same straight-line numbers as the GT2, but it only saves one run and you can't download data to a PC.
We'd opt for the GT2. The PocketDYNO is a small box about the size of a three-by-five card that we mounted to each vehicle's center console with Velcro. It feeds data to a handheld computer a Palm, a Pocket PC, or a laptop. Its unobtrusive size is appealing, and it's one of only two units in this test that won't take up any windshield real estate. Therefore, the closer it is to level and square to the car, the more accurate it will be. You can choose a speed run, a distance run, or a g measurement.
During a speed run, the PocketDYNO measures the 0-to time and then estimates a quarter-mile time and speed based on the 0-tomph data. The distance run measures quarter-mile times, and the g measurement can store up to 20 seconds of data and display peak g in four directions.
The PocketDYNO's calculations turned out to be slower than the authoritative drag-strip times in both vehicles, off by 0. Some runs got within 0. Its only adjustment for rollout is start speed, but even with changes, this meter's accuracy did not improve. However, the estimated quarter-mile function is a good idea—a driver is less likely to attract cops when doing 0-to runs on public roads—and was more accurate than the PocketDYNO's actual quarter-mile measurements during our tests.
The estimated quarter-mile times were 0. In the G6 it was 0. For starters, it's the only one of the accelerometer-based units that measures acceleration in the vertical plane. Theoretically, that means the G-tech can detect how dramatically the car pitches during an acceleration run and automatically correct for it. There is a calibration procedure that supposedly makes the G-tech's quarter-mile speed readings more closely match those of the drag lights.
We performed the prescribed calibration, but interestingly, we found the procedure increased accuracy only when the G-tech was installed in the Envoy. That quibble aside, the G-tech has two unique features. It has shift lights that flash at a designated rpm to signal when it's time to shift gears.
Had I known this 20 years ago, I could have spared several driveshafts from an untimely death. Today, thanks to computer-controlled automatic transmissions and launch-control software, you need neither talent nor practice to bang out a 3-second run to When was the last time you actually used launch control?
More often than not, real drag races happen with little notice at a traffic light. Leave your car in Drive and floor it, and the result can look very different from what 0-to times suggest. Thanks to turbo lag, slow-to-respond powertrain computers, overly aggressive traction-control systems, and transmissions programmed for shift comfort even at wide-open throttle, the car you expect to win might lose—and it might do so dramatically.
With turbocharged horsepower, all-wheel drive, and a blazing 4. When the light turns green, you and the Mustang driver each floor it, but the Ford leaves the Bimmer for dead. In , this magazine began performing the ingenious rolling 5-to test invented by our sister magazine, Car and Driver. Or both. These times are published in every magazine and in every road test, but I struggle to figure out what they really measure.
When was the last time you needed to get to 60 mph as quickly as your car allows? Or probably just that one time when you wanted to see whether your car actually could do it in the 8. That inevitably breaks things. Even Nissan threw out warranty claims of some GT-R owners who had been playing with the launch control systems too frequently.
On your third attempt, the car will snap. Take the BMW i as an example. With the engine running, step on the brake with your left foot.
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