The same Formula One techniques – and engineers – that make race cars go faster are now helping the all-new Ford Ranger slice through the air cleaner, ensuring the compact pickup delivers one of the best fuel economy figures in the segment.
Using the same cutting-edge simulation software as Formula One teams, they performed more than 1000 full-vehicle aerodynamic simulations to perfect the shape of Ranger for fuel efficiency.
“The pickup’s ride height, especially in the 4x4 models, was another challenge. The higher the vehicle, the more aerodynamic drag it has to overcome. It’s a big number of ‘counts’ for every millimetre of ride height.”
A drag count is a single unit of drag. A drag count of 1 is equal to a drag coefficient of 0.001. The drag coefficient measures a vehicle’s resistance to the air through which it passes – the higher the number, the more the engine works and the more fuel it burns.
Working with the designers, the aerodynamics team managed to pare Ranger’s drag coefficient down to a very competitive ratio of 0.40 by implementing the most efficient design. They optimised the A-pillars, tapered the C-pillars and added a small spoiler to the top of the tailgate.
“With about 60% of the power required to cruise at highway speeds being used to overcome aerodynamic effects, minimising drag has real-world fuel economy benefits for the customer, translating directly into more dollars in their pockets,” said Dr. Lewington, senior aerodynamicist.
Faster turnaround of designs
In the past, before the advent of computational models, designing an aerodynamic vehicle was a time-consuming and expensive process. Engineers would build a clay model, typically a quarter-scale model, take that into a wind tunnel and optimise its shape by modelling or manipulating the clay on the vehicle. The engineers might be able to get through 15 to 20 changes in one day at the wind tunnel but the lead up to that could be three to four months.
But by using computational fluid dynamics simulation software that models the entire flow field around a vehicle, Ford’s aerodynamics team is able to optimise a design by running up to 50 simulations in just two weeks. On the Ranger, they were able to complete most of the design in the computer before building a full-scale prototype for fine-tuning, hence reducing costly wind tunnel testing by a third.
The computational models also bring aerodynamics to life for the designers and other engineers as they can now visually see the flow field around the vehicle instead of having to make decisions based on only numbers or graphs.
The ease of the methodology gave Ranger a big boost halfway through the programme when an executive decision was made to push the pickup’s fuel economy figures beyond the original targets. The aerodynamics team pitched in and shaved another 10% off the vehicle drag – a sizeable reduction mid-way through any vehicle programme.
“Without the computer technology, it would have been much more difficult, as we’d have had to go back into the wind tunnel to test prototype parts. There was very little time as the other teams were ready to kick off tooling and we had to give them the answer very quickly,” recalled Dr. Lewington.
While designing trucks that conserve energy can’t seem more different from designing speedsters that break the sound barrier, both aerodynamicists insist that the physics remains the same.
“In Formula One, we chase seconds, or even hundredths of seconds,” said Maertens. “On the Ranger, we chase down every last count of drag.”