Debunking Tuning Myths
The evolution of cell phones never ceases to amaze us. In Carter's day, the addition of a retractable antenna, Pong and text messaging astonished the masses. In most of ours, it was instant messaging, limited web access and GPS nav. Today, with the release of advanced PDAs like the iPhone, there seems to be no limit to manufacturer features, optional services, and downloadable upgrades. Enter the latest: Dynolicious' Auto Performance Meter software for the iPhone and iPod, that claims to measure any car's horsepower and quarter mile acceleration.
Replacing A Drag Strip & Dyno With An Iphone?
Does it really work? And by "work", we mean, "is it at all accurate?" Late model iPhones and iPods use accelerometers to communicate the device's orientation to its display, so that if you turn your device on its side, the screen switches its display from vertical to horizontal, and vise versa. Dynolicious claims that its software can use either device's built-in accelerometers to track a vehicle's acceleration, and by plotting these movements over time and adjusting for vehicle weight, wheel horsepower and acceleration can be inferred.
Dynolicious' assumption is logical, but based entirely upon the accuracy of the iPod or iPhone's accelerometers, and the ability of the user to follow simple instructions. To put their product to the test, we procured a supercharged '08 xB test car, an iPhone loaded with Dynolicious' $13 software, and visited the local dyno and dragstrip.
Our fist order of business was to calibrate our iPhone. We followed Dynolicious' on-screen calibration instructions precisely, and input our vehicle's 3,355-pound weight, taken by G-Dimension's Intercomp corner weights.
Next, we visited the Dynojet dynamometer of MD Automotive, and rolled out three baseline runs of our xB, for ending average figures of 210.3 whp and 186.6 lb-ft of torque.
Finally, we visited the 1/8 mile drag strip at Irwindale, Calif.'s Toyota Motor Speedway, where we secured our iPhone in the xB's cup holder (also, as per Dynolicious instructions), performed a hellacious 2nd gear burnout (click importtuner.com for the vid), and powered down the 1/8 mile to a email@example.com.
After the smoke had cleared, and we began down the return lane back to the staging area, we glanced down at our Dynolicious-loaded iPhone: 10.45 sec @ 73.1 MPH, and a peak horsepower number of 175 - nearly three tenths of a seconds and three mph off our official time, and 35.3 whp away from actual dyno numbers.
Since horsepower numbers inferred by our Dynolicious-loaded iPhone were so far off their actual values-by 35.3 whp on average; a 16.8% variance-we were really leaning toward classifying this product as fiction. But because its 1/8th mile E.T. and trap speeds were quite close to their actual readings - only a 2.5% variance in E.T., and 3.4% for trap speed - we're going to give Dynolicious the benefit of our doubt and concede that there might be some truth in their claims. In fact, we suspect the accuracy of the system is mainly limited by the state of the particular iPod or iPhone the program is loaded onto, and how sturdily the device is secured in the vehicle. Follow Dynolicious' calibration and installation instructions, be careful not to drop or damage your device, and look forward to a rough picture of how fast your vehicle is. As for measuring its power... you'd be best to visit a dyno.
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