What We Measure

• You can use PowerCurve to measure the speed, acceleration, power and torque of your vehicle. You can also choose a desired speed, a time period or a distance over which the test will run. You can even configure PowerCurve to automatically stop when you begin to decelerate.

Configuration Options

• PowerCurve takes into account the width, height, weight and wheel radius of your vehicle when performing its calculations. These defaults are sensible, but for more accurate results you can modify these properties to more closely match those of your vehicle. It is also possible to specify the air pressure and temperature to further fine tune PowerCurve.

How We Display It

• PowerCurve lets you choose between displaying one or two graphs, each of which displays the measurement of interest on the Y-axis and time on the X-axis. We update these graphs in real time, giving you immediate feedback. You can also view statistics for the most recent run, or you can view your best performances for each measurement.

Save And Load

• PowerCurve enables you to save and load previously recorded runs when ever you want providing a safer and more convenient user experience.

Safety Instructions

• Do not attempt to use PowerCurve while driving alone. We recommend that you have a passenger with you, operating the application at all times
• You can take advantage of the auto-stop settings to safely start and stop the recording if driving alone.
• Please drive responsibly and follow the road code at all times
• The developers and distributors of PowerCurve take no responsibility for accidents, injuries or property damage that may occur during its use

Viewing Graphs

• The yellow bar marks the selected point. Touch the graph to select a new point.
• The number in the upper right corner represents the value at the selected point.
• Touch and drag the graph to scroll back and forth through the data.
• Zoom in and out by pinching on the graph.
• Please not that Scroll, Zoom and Select are disabled while PowerCurve is recording a run.

Calibration

To ensure accurate calculations, Powercurve needs to be calibrated for run conditions. Before starting a run, place your iPhone/iPod touch at the orientaion that it will be for the entire run. Now you can either:

• Manually Calbrate - Run a three second calibration by going to the CALIBRATION page in the Setup tab.
• Use Auto-Calibration - Turn on Auto-Calibration from the RUN page in the Setup tab. A three second calibration cycle is then run for you at the start of each recording.

Keep your iPhone/iPod Touch still during calibration and at a constant orientation for the entire run.

Using Auto Stop

PowerCurve can automatically stop a run recording when certain criteria are met. Just set the desired Auto Stop Condition from the RUN page in Setup.

The stopping condiditons are:

• Speed - Recording will stop as soon as the Target Speed is reached.
• Distance - Recording will stop when you have travelled the Target Distance.
• Both - Recording will stop when either speed or distance criteria have been met.

Car Measurements

• Wheel Radius is taken as the distance from the center of the wheel to the ground.
• The weight of an average 4 door sedan is around 1200kg (2700lb).

Gear Ratio

To calculate Power and Torque, Power Curve needs an approximation of the gear ratio of your vehicle. To get a rough estimate of your gear ratio you will need to know the revolutions per minute (RPM) of your vehicles engine at a particular speed.

Once you have these values, enter them into the Gear Ratio Calculator in the Gear Ratio page of the on-iPhone/iPod help.

Drag Coefficient

The Drag Coefficient (Cd) is a measure of how streamlined your vehile is. A lower value indicates a more streamlined vehicle.

The typical modern car will have a drag coefficient between 0.3 and 0.35. SUV's have significantly higher drag coefficients due to their large box shape (0.35 - 0.45).

Frontal area and windshield incline are the main causes of variation in drag coefficient between vehicles. A table of drag coefficient for common makes of cars can be found on Wikipedia under "Automobile Drag Coefficient".

Air Temperature and Pressure

PowerCurve uses approximations of air temperature and pressuer to better calculate forces acting on your car during runs

The default values are as follows

• Pressure - Standard atmospheric pressure, 1013 hPa (metric) or 30 Hg (Imperial).
• Temperature - The temperature on a warm day, 20*C (metric) or 68*F (Imperial).

Both Air Pressure and Temperature can be set in the ADVANCED page from the Setup tab.