The car weight is one of the most important data PerfExpert takes into account when calculating dyno results. It has a direct effect on the displayed horsepower and torque.
In this article we will see:
- how to set the Curb weight parameter in the car profile,
- how to use the Fuel level and additional weights test preparation screen,
- and how to weigh your car for more accurate dyno results.
1. Setting the ‘Curb weight’ parameter
The Curb weight parameter can be edited in the car profile screen. Weight unit can be defined in the Settings screen.
The curb weight is the "total weight of a vehicle with standard equipment, all necessary operating consumables (e.g., motor oil and coolant), a full tank of fuel, while not loaded with either passengers or cargo" as explained in the Wikipedia definition. This means you must not include, neither your own weight nor fuel weight in this value. This is also exactly how PerfExpert considers the Curb weight parameter in the car profile, and you must have this definition in mind to understand how the fuel level impacts the car weight.
The curb weight is usually provided by the car manufacturer and can be found in the manual, in the registration document or on car databases like AutoRef, Automobile-Catalog, or ZePerfs. For instance, in France, you will find the curb weight of a car on it’s registration document, at the G.1 legend. Feel free to comment here to tell us where can be found the curb weight on car legal documents in your country.
Unfortunately, some countries may have slightly different definitions of the curb weight, considering the fuel tank is filled at 90%, or considering it includes a 75 Kg passenger. Also, some manufacturers just advertise a base curb weight, that means the curb weight of the vehicle with only the base trim features installed, not the optional equipment (sunroof for example).
As you can see, although the manufacturer advertised curb weight is a good value to start with, it can sometimes be uncertain, especially if you modified your car. If you want to get the actual horsepower realistically, you will need to weigh your car at some point. PerfExpert lets you update the curb weight parameter on existing results to get the horsepower and torque re-calculated. So don’t worry about doing measurements right now even if you are not sure about the exact curb weight.
2. Using the ‘Fuel level and additional weights’ screen
This test preparation screen lets you describe exactly the current weight configuration of your car before each test session.
Before you start each test session, you just have to enter the current weight configuration for your car. This allows PerfExpert to calculate the total car weight for you.
Enter each passenger’s weight, including the driver’s one. Tap the ADD button to enter a new passenger. Those weights will be added to the curb weight of the car.
It’s better that the car doesn’t have any cargo when you test it. Anyway, if there is cargo, estimate its weight (or weigh it) and enter the value in the ‘Cargo’ field.
Now, set the Fuel level by making the slider matching the current fuel tank filling percentage.
Note that any value under 100% will subtract weight from the curb weight, as the curb weight is the weight of the car with fuel level at 100%.
For PerfExpert to calculate accurately the missing fuel weight, you have to make sure the Fuel type and the Fuel tank capacity parameters of your car profile are properly defined.
The Total Weight is automatically displayed at the bottom of the screen.
3. Weighing your car for more accuracy
That's the way to go the get more accurate results! This can be done at a motorsport garage or club, using specific weighing scales. Feel free to comment to mention any garage that has this kind of scales available.
Of course, when weighing your car, you must ensure it meets exactly all the requirements for the curb weight definition :
- The car must not be loaded with either passengers or cargo (not even the driver)
- All liquids must be level (engine oil, coolant, brake fluid...)
- Fuel tank must be full
Here we get 1238 Kg for a french 2013 Toyota GT86 that has a Milltek catback resonated exhaust and a Cosworth air filter in OEM air box.
Feel free to comment and register !