Horsepower and Torque can be measured quite accurately though the app "Torque" - measurements taken are 'at the wheels', not at the flywheel
It is quite important to fill out the vehicle profile for this with the correct weight of the vehicle - using the manufacturers advertised weight unfortunately won't be close to your real weight as it often does not include differing specifications of the same vehicle (alloy wheels vs steel wheel weights for example). The most accurate way to weigh your vehicle is on a weighbridge.
Alternatively, you can approximate from the manufacturers specification, plus your weight, plus the weight of the fuel, plus the weight of any extra equipment in the vehicle.
How to do the test
Firstly, make sure you abide by all local laws and make sure that you are safe at all times!
The test should be performed on a flat track. Going up or down a hill/slope will lead to inaccurate readings.
Start from a slow rolling start (about 5 to 10mph) and accelerate until about 55mph. This will give you the most accurate peak value for your vehicle.
Note: If you spin the vehicle wheels then this will cause the figures to over-read
For best results on older vehicles (or vehicles with a slow sensor refresh) make sure that:
- Faster Communication is enabled in the app settings
- Only have the displays you are interested on the screen - the more displays you have visible, the slower the sensor update and this can degrade the accuracy of the HP/Torque readings on slower ECUs