Explaining the VECTO drag calculator19 May 2020

Consultancy AirShaper explains how the EU VECTO tool estimates a key factor in vehicles' carbon emissions: their air drag.

It says: that the Vehicle Energy Consumption calculation Tool, or VECTO in short, is a mandatory tool since January 2019 for new trucks & buses in a number of categories.

Based on input parameters like rolling resistance, air drag, masses and inertia, gearbox friction, auxiliary power and engine performance, it simulates fuel consumption and CO2 emissions based on standardised driving cycles. So how do you obtain all these parameters?

Based on constant speed track tests and a massive set of measurement data, the VECTO AirDrag tool allows you to calculate the air drag Cd*A - based on force measurements:

- Constant forces, that do not change with velocity (rolling resistance, bearing losses, and so on)

- Air drag force, which scales with the square of the velocity.

To obtain the split between these forces, you can measure the force at two different velocities. If you then fit a curve through both low-speed and high-speed tests, including a constant and a quadratic term, you can isolate both components.

William Dalrymple

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