PerfExpert is a smartphone application for measuring car performance with high reliability. It allows any car owner to measure acceleration times and power with amazing accuracy regarding its price and the equipment used : a "simple" smartphone !

A User Guide is available online from the application and allows a quick start. It explains the basic principles of setting the application, the car sheets, the measurement procedure ...

 

Based on both accelerometer...

PerfExpert uses both the accelerometer of your smartphone and information about your car (that you enter in advance) to calculate engine power and torque and acceleration times. According to our experience, the use of the accelerometer (and not the GPS receiver) is the best choice for such an automobile performance smartphone application. You can read more in the related topic in the FAQ.

 

...and technical data to enter

You are prompted to enter information about your vehicle in a "car sheet" to be used by PerfExpert for its calculations. We have reduced the amount of data to a minimum in order to facilitate the correct entry while maintaining excellent results accuracy. Therefore PerfExpert offers three types of sheet ("Basic", "Simple" and "Advanced") allowing to set properly the application according to the amount of information you have. For Dyno measurements, we strongly recommend the choice of the "Advanced" sheet for best results. Indeed, with this sheet, a larger number of parameters are taken into account in the calculations so the results are more realistic.

 

Two operating modes

PerfExpert has two main functions : Timed Run measurements and Dyno (Power) measurements. These two functions are clearly distinguished and separated in PerfExpert, unlike other applications that "blend" the two. In fact when performing a measurement, the user must tell the application whether to make a timed run (0 to 60Mph, 1/4mile ...) or dyno measuremen, it can't do both at once. We chose to separate the two because it's essential to follow different measurement procedures in order to successfully realize one or the other! See the Test section in the Guide for more information.

 

A real dyno

When PerfExpert is used with rigor and in good conditions (See Test section in the Guide), it constitutes a real embedded dyno that can provide results similar to those of a good chassis dynamometer.

We emphasize that PerfExpert only gives "flywheel" power (engine power), and not power "at the wheels". Of course, this is not a direct measurement : this is impossible by definition as the car accelerates on the road through the wheels, and it occurs not only immeasurable losses between engine and the wheels (transmission losses, losses due to rotary inertia), but it is also difficult to measure losses due to the external environment (air resistance and rolling resistance). PerfExpert therefore makes a very realistic dynamic calculation of all these losses to retrieve flywheel power from the power actually measured. The loss calculation is done as comprehensively as possible considering all kind of engine power lossThus, using the "Advanced" sheet, you are not asked to enter yourself a loss percentage, PefExpert calculate it for you, unlike other applications.

PerfExpert performs a power correction depending on the weather conditions at the time of measurement, in order to to bring back the power of your engine to the power it would produce in normalized atmospheric conditions, as engine manufacturers do. You can use one of five international standards currently in use :DIN 70020, SAE J1349, EEC / E, JIS D 1001, and ISO 1585. Again, on this point, PerfExpert innovates by offering this kind of function that are used on most chassis dynamometers.