• Frequently Asked Questions

    If you can't find your answer here, feel free to contact us

    Do I need to connect PerfExpert to my car ?

    No, you don't need to connect your phone to your car electronics.


    In the default measurement mode, PerfExpert relies on the internal accelerometer sensor of your phone to measure the actual acceleration of your car. This requires that your phone is firmly mounted inside your car, and that each measurement can only be started from complete halt (0Mph). This way, PerfExpert can calculates accurately the instantaneous car speed and acceleration and during measurement. For best results, PerfExpert use your phone internal accelerometer at its maximum frequency (up to 200Hz on some premium devices).


    With the optional VBS mode, PerfExpert can rely on data provided in real time by the Racelogic VBox Sport 20Hz external GPS. This allows measurements without the need to mount your phone, and without the need to stop the car before starting each measurement, for example to perform dyno tests from a rolling start. Thanks to the VBox Sport, PerfExpert know accurately the instantaneous car speed and acceleration during measurement. For now, the VBS mode is only available in PerfExpert for iOS Beta.

    How PerfExpert can estimate my engine power and torque ?

    PerfExpert prompt you to provide your car characteristics by creating and filling-in your car profile. Then, from both the measured acceleration and the car profile parameters, PerfExpert can estimate power and torque thanks to our physical model.

    This model takes into losses between engine and the wheels (transmission, rotary inertia), and also losses due to the external environment (air resistance and rolling resistance). PerfExpert therefore perform a realistic estimation of all these losses to retrieve flywheel power from the power actually measured.

    How does PerfExpert know the engine rev, as it's not connected to the car ?

    From the information you entered in the car profile, PerfExpert know the overall ratio of your car transmission. So from the car speed, PerfExpert can compute back the engine rev.

    Does PerfExpert manage the influence of atmospheric condition on engine performance ?

    Yes, PerfExpert apply a correction ratio to power, based 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, CEE/E, JIS D 1001, and ISO 1585.

    What result accuracy can I expect from PerfExpert ?

    This accuracy not only depends on PerfExpert or the smartphone used, but also on how rigorous you are while performing the measurement procedure. It also depends on the in-car phone mounting quality. Following perfectly the measurement procedure, results accuracy can reach 0.5% for Timed runs and 2% for dyno tests.

    You can see some examples of PerfExpert results compared to other expensive systems results on this topic of our forum.

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