Above all, we put the emphasis on a fundamental point : even if this app combines a high technicity level with a very easy-to-use side, it does need to be well used, and in this way, it’s essential to completely read this guide before its first use… Don’t forget that any on-board measure system will never give good results (or at least the ones it should give with a perfect use) if used the wrong way or misunderstood. That’s why they need to be very correctly used, and our app isn’t an exception to this rule! We invite you to completely read this guide before any first use of our app… Thank you, and have a nice reading!



1.1 Calibration

1.2 Units

1.3 Trigger

1.4 Weather Correction

1.5 Weather Data

1.6 Smoothing

1.7 Disable vibrator

Creating and selecting a car

2.1 Create a car

2.2 Select a car

2.3 Modify a car

2.4 Delete a car

Mounting the Phone


4.1 Measurement conditions

4.2 Type of measurement

4.3 Perform the measurement

4.3.1 Timed Run (accelerations)

4.3.2 Dyno Run (power)


5.1 Read a result

5.2 Delete a result



1 Settings

The first operation consists in correctly setting up the app. To reach « Settings» screen from « Test » screen (main screen), press the « Menu » button, then select « Settings ». The list of the settings to do appears. These settings ideally have to be done in the order shown below.


1.1 Calibration

Click on « Calibration » and follow the instructions shown on the screen. To do a good calibration you ideally need to use a perfect horizontal surface and a small box (like the original box of your phone) making a right angle with this surface. However, our calibration procedure allows to accept a slightly angle surface. You’ll have to stabilize your phone in 9 precise positions, and a vibration will occur at each registered position. For each of these positions, you’ll have 10 seconds to correctly stabilize the phone (a countdown will appear on screen), and the calibration will be done during the 11th second. During this calibration second the phone must keep stable. The registering of the calibration of each position will be signified by a vibration. At the 9th step, PerfExpert will ask you to stabilize your phone in any angle position (ideally making a 45° angle with vertical), in order to verify the quality of your calibration. If correct, calibration is accepted and then you return to « Settings » screen by pressing the OK button, but if incorrect, you’ll have to do it again.


1.2 Units

Click on « Units ». A list of physical variables appears, you have for each of them to choose its unit (metric or imperial in general), by clicking on the concerned variable, and then selecting the wanted unit in the list which appears. Once all units chosen, you come back to « Settings » screen by pressing the Return key.


1.3 Trigger

Click on « Trigger », and choose the level of acceleration you want the chrono to start. For a first use, let the default value.


1.4 Weather Correction

Check the box “Power correction” if you want to enable it, else uncheck it. We recommend to let it enabled, for the most accurate results : indeed, this correction allows to bring back the power of your engine to the power it would produce in the atmospheric conditions defined by this norm. If you choose to enable the power correction, you’ll have to choose the correction norm that you want to use, by selecting it in “Correction norm”. You can choose between the five international norms actually used : DIN 70020, SAE J1349, JIS D1001, EEC / E, ISO 1585.


1.5 Weather Data

Check the box « Enter values manually » if you want to manually enter the weather data (atmospherics pressure and temperature, relative humidity rate of the air), uncheck it if you want these data to be automatically retrieved by the app. We recommend to let this box unchecked, for the most accurate results, unless the app cannot connect to server, or the geolocation by networks isn’t available : in these cases, you’ll have to check it and enter yourself the weather data.

1.6 Smoothing

Click on « Smoothing », and choose the most adapted smoothing level. We recommend to systematically use a medium smoothing, that is which we have set after serious study as giving the best results in most measure conditions. Other smoothings exclusively correspond to extreme cases. However, we indicate the uses for each smoothing :

  • Low smoothing (not recommended) : Only perfectly smooth roads & perfect mounting & power measurements only on the second gear
  • Medium smoothing (recommended): All types of roads from medium to perfect & excellent mounting but slight imperfection tolerated & power measurements on the second or third gear
  • High smoothing (reserved for poor measurement conditions): Bad Roads & imperfect mounting & power measurements only on the second gear.

1.7 Disable vibrator

Check the box « Disable vibrator » if you want it to be inactive during the measure (seriously recommended) in order to prevent the phone from vibrating at an incoming call for example, else uncheck it.


2 Creating and selecting a car

The second operation to achieve is to “create” one (or more) car in the app, by filling a vehicle sheet which contain all the information necessary to identify it, and calculate its acceleration and power. To access to the “My Cars” screen from the “Test” screen, press the "Menu" button, then select "My Cars". The list of registered cars will be displayed.


2.1 Create a car

To create a first car, or add one, press the "Menu" button, then select "Add sheet". It offers the choice between three sheets, corresponding to the level of information you have on the car to measure : "basic"sheet, “simplified” sheet, and “advanced” sheet. If you don’t have any information on your car, choose the "Basic" sheet, if you have only summary data, choose the "Simplified" sheet, and if you have all the data required for accurate measurements of power (dyno), choose the "Advanced" sheet. You may need to know that with a "Basic" sheet, you can only do accelerations (timed runs) : indeed, it is necessary to know a minimum of data to make power measurements, as they are only available with the "simplified" and "advanced" sheets. The table below summarize the situation :





Static losses


Dynamic losses

« Basic » sheet




« Simplified » sheet




« Advanced » sheet





Once you have chosen the wanted sheet, you will then see a vehicle sheet with default values that you’ll have to fill in. Once the sheet entirely completed, press “OK” to validate it, and then you return to the "MyCars" screen.


2.2 Select a car

This is done from the screen "Test" by clicking on the dropdown list "Cars" just above the speedometer, which then shows the list of registered cars, then click on the car you want to select. This selection is important because this is the one that the app will register as the "current" car : this means that any further measurement you’ll do will be systematically used with this car by the app, and all results you will find in the "Results" menu will be those of this car.


2.3 Modify a car

You can modify a vehicle sheet at any time by clicking on the desired car from the "My Cars" screen. Once changes done, return to the "My Cars" screen by pressing the "OK" button.


2.4 Delete a car

You can also delete a car at any time by doing a long click on the car you want to delete from the "My Cars" screen, and selecting "Delete" from the context menu that appears. Please note that this operation is irreversible, and deletes in the same time all the results associated with this car.


3 Mounting the Phone

Perfectly mount the phone in the car, by following these three rules :

  • It absolutely must not move during the measurement
  • It must be submitted at least possible vibrations
  • It must be aligned with the direction of travel of the vehicle and not inclined laterally, but can be tilted vertically from 0 to 90 ° from the horizontal
Here is a diagram showing you the direction that should have your phone in the car :
Allowed phone mounting position in the car

The key point to remember is that the phone must be perfectly still during measurement, this is the most important point, and the only way to achieve it is by putting your phone in a suitable support, and making sure that this support is firmly secured in the cockpit. A simple (and free!) trick is to use as support the original box of your phone, and to jam your phone against the side walls of the box with wedges, and just put this box on the passenger seat. You must align it with the direction of travel, and chock it against the back : if you speed well in a straight line, acceleration will firmly secure the box against the back, and your measurements will be excellent! You can also, to ensure a good stability, stall in addition the box with heavy objects located on its sides and / or in front of it.


4 Test

Once the phone secured in the car, and after checking the selected car (displayed at the top of the "Test" screen) is the one you want to measure, you have to do the following.


4.1 Measurement conditions

You have to measure on a road as plane and flat as possible, in a straight line, in the absence (or near absence) of wind, and with warmed and well inflated tyres (manufacturer pressure). And ALWAYS leave from a full stop, this is a FUNDAMENTAL point!


4.2 Type of measurement

Select on "Test" screen the type of measurement desired : TIMED RUN  or DYNO.


4.3 Perform the measurement

 you're ready to perform the measurement : car well stabilized and stopped at the chosen starting point, make sure your foot is not on the brake and the hand brake is not pulled, clutch disengaged and first gear engaged, press the "Start" button located in the middle of the "Test" screen. The inscription "Wait" is displayed in red for a second, time during which you mustn’t move. Then the inscription "Go" appears in green : so you can leave whenever you want, the app will identify the precise moment of the start, and the timer will start immediately. In all cases, the timer (and thus the measure) will stop automatically after the first of the three following conditions met : 500 meters traveled, heavy braking, or a simple lift of the foot extended for more than 3 seconds. So you don't have to worry about anything else that your drive during the measurement, the app takes care of everything else!


4.3.1 Timed Run (accelerations)

Only one thing to do : crank up the speed, applying the best in you to blow up the clock (but not the app, in any case you will not succeed, even with 1000 hp!).


4.3.2 Dyno Run (power)

Leave slowly in first gear, pass quickly the second or third gear (depending on the gear filled in the vehicle sheet), making sure to fall under the measure beginning rev (see sheet). Then get full throttle up to the maximum rev. Once this maximum rev reached, put the car as soon as possible in coastdown (it is useless to continue to accelerate), and brake if you want : the app will understand in each case that the measurement has ended, and will stop the clock. We put the emphasis on the fact that you must cross the measure beginning rev at full throttle , and in the wanted gear for the power measurement. Ideally, get full throttle 500 rpm before the measure beginning rev (exemple: at 1500 rpm for a 2000 rpm measure beginning rev).


5 Results

Once the measurement or the session is completed, you can see the results of your car. You can access to the "Results List" screen from :
- "Test" screen by pressing the "Menu" button then "Results"
- "My cars" screen, making a long click on the car you want, and "Results".


5.1 Read a result

Click on the desired result (indicated by the date and time of measurement associated), and you access to the results sheet. The type of result depends on the type of measurement performed (timed run or dyno), but the result sheet contains in all cases two parts : a "Results"part at the top of the sheet that displays the textual results, and a “Curves” part at the bottom of the sheet that displays a small graph which is the “miniature” version of the measurement curves. By clicking on this graph, you reach the full screen detailled graph. This graph has a very interesting feature: it is interactive, meaning that you can instantly get access to all the values of the measure simply by clicking on it in the right place! You then return to the result sheet by pressing the Return key, and the "Results List" screen by pressing again the Return key.


5.2 Delete a result

You can delete a result by selecting it from the "Results List" screen with a long click and selecting "Delete" from the context menu that appears. Please note that this operation is irreversible!