Bumpers: What Impact on the Autonomy of an Electric Car?

The aerodynamic and energy impact of installing mud flaps is not without consequences on air resistance and therefore on range.

You don’t need to be a great aerodynamic engineer to know that any appendage that disrupts the airflow around a car (or a plane, a train, a rocket…) modifies its movement. Open the window and put your hand out on the highway; the effect is immediate. The same goes for the installation of mud flaps to protect the bodywork of your electric car.

Aerodynamic Impact

1. Increased Drag: Mud flaps increase the frontal area and disrupt the airflow around the wheels and the lower body. This disturbance increases the aerodynamic drag of the vehicle.
2. Drag Coefficient (Cd): The drag coefficient is a measure of a vehicle’s aerodynamic efficiency. Adding mud flaps may slightly increase this coefficient, leading to a decrease in aerodynamic efficiency.

Energy Impact

1. Energy Consumption: Due to the increased drag, the electric motor of the Tesla Model Y will have to work harder to maintain the same speed, which increases its energy consumption.
2. Reduced Range: An increase in energy consumption directly translates to a reduction in the vehicle’s range. According to studies and simulations, minor modifications like adding mud flaps can decrease the range by about 2%, although this may vary based on specific driving conditions and flap design.

What impact on a Tesla Model Y?

Let’s then take a working hypothesis that resonates with everyone: the Tesla Model Y Propulsion with an initial range of 450 km without mud flaps. Its standard drag coefficient (Cd) is 0.23.

1. Energy Consumption without Mud Flaps: 75 kWh / 450 km = 166.67 Wh/km
2. Energy Consumption with Mud Flaps: Increase of 0.02 in Cd = 166.67 Wh/km * 1.02 = 169.97 Wh/km
3. New Range with Mud Flaps: Range with an increase of 0.02 in Cd = 75 kWh / 169.97 Wh/km ≈ 441.19 km

The addition of mud flaps on a Tesla Model Y would therefore result in a reduction of range by about 9 km, which corresponds to a 2% reduction in range. This decrease is relatively small compared to the protective benefits they provide.

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