Car test using iPhone

Apple's iPhone has received significant attention as a diverse tool for many different tasks. Developers have taken advantage of the many unique features offered by the iPhone, showing this phone to be capable of much more than you would expect. BunsenTech demonstrated this with Dynolicious, an iPhone app capable of producing vehicle performance data including acceleration times, elapsed time (by distance), lateral G force, and horsepower. MyRide.com used Dynolicious to road test the 2008 Smart Passion Cabriolet.

When apple engineers included a sensitive three-axis accelerometer to the iPhone platform, they may have just needed a sensor that could interpret the phone's physical orientation to flip the screen accordingly, or as a specialized input for games. Dynolicious uses the same feature to graph several types of vehicle performance data. MyRide claimed the sensitivity of the accelerometer allowed Dynolicious to show consistent data through multiple tests of the Smart car.

Three elements are utilized in the accelerometer, a silicon mass, set of silicon springs, and electrical current. The springs measure the position of the silicon mass using the electrical current. Moving the iPhone fluctuates the current that passes through the springs. These fluctuations are converted into data that can be used by apps with enough precision to compare small changes in vehicle performance, such as the inherent performance drop when a vehicle's A/C is running.

Dynolicious samples the accelerometer data as much as 100 times per second to create a detailed picture of the car's acceleration. The speed of the vehicle and distance traveled can be extrapolated from the data. Performance measurements include speed tests from 0-10 MPH through 0-100 MPH, quarter mile elapsed time, quarter mile trap speed, elapsed time and trap speed for standard intervals (60', 330', 1/8 Mi, 1000'), lateral G's (current and peak), braking G's (current and peak), wheel horsepower, and estimated engine horsepower. Horsepower measurements take into account the weight of the car compared with the acceleration.

Performance results recorded on Dynolicious for the Smart car showed a 0-60 MPH time of 13.6 sec. According to MyRide, the app sensed the differences in acceleration times between the car's automatic and manual shift modes, and with the A/C switched on or off. Tests on a 200-ft. skidpad showed the Smart car handle .78g before sliding. Panic braking from 60 MPH brought a force of .83g, and full acceleration was recorded at .45g. Horsepower at the wheel was shown to be 61hp, which MyRide claimed was probably fairly accurate considering the company listed the engine HP as 71 and a 13%-17% loss of horsepower to the drivetrain in most vehicles is expected.

Presentation of Dynolicious data is displayed on realtime speedometer and graphs, or a realtime skidpad display. Results of any run can be saved and compared. Vehicle profiles are saved, allowing averages to be interpreted for each vehicle through a number of tests. Results can be compared between vehicles, dates, or before and after modifications.

The device must be calibrated before use for maximum accuracy. MyRide claimed consistent results between tests, but a full report using professional testing equipment to determine the actual accuracy of the program should be posted on the Dynolicious site in the future. Dynolicious is available at Apple's App store for $13.

by MacNN Staff