While Renault prepared an amazing subcompact for the Paris Motor Show that will become reality in a decade, Citroën based its 117 mpg car on the existing C4 Cactus.
The French automotive industry as a whole is working on a future in which cars don’t need more than 2 liters of fuel/100 km. That would be 117 mpg in American (sort of, fuel economy ratings vary wildly by region).
While the C4 Cactus is already 440 pounds lighter than the C4 hatchback, the Airflow lost another 220 by using aluminum for the upper cowl panel, inner side members and rear floor pan, high-yield steels for the front side rails and heel board, and composite materials for the front of the floor. These are structural parts and Citroën claims that not only do they help to soak up energy in the event of an impact, but also meet the highest standards in terms of mechanical strength.
Because aluminum and carbon fiber have a significantly lower bulk and density (around 2,700kg/m3 for aluminum and around 1,200 kg/m3 for carbon, compared with 7,800kg/m3 for steel), carbon-based composite materials have been used for the suspension springs, tailgate, rear bench, side panels, roof, roof cross-members, wings and doors. Aluminum is used for the engine cradle while the bonnet is the same as for the production C4 Cactus, which already uses aluminum.
What’s more, new processes were introduced in order to reduce the thickness of the tubes and cups in the exhaust system. Translucent polycarbonate was used for the panoramic sunroof, and carbon fiber on the Airpump panels.
Speaking of air pumps, the C4 Airflow’s drivetrain includes a friction-optimized 3-cylinder gas engine, a compressed air energy storage unit, a hydraulic pump/motor unit and an automatic transmission with an epicyclic gear train. The zero emission mode uses compressed air only, but you can also switch to gas-only mode or combined power. LEDs all around make sure you don’t waste too much energy on lights.
The body also got some upgrades in order to slice through the air like an arrow. Variable-geometry components include a new front bumper with three air intakes that continuously adjust in accordance with speed, regulating the airflow. Mobile side deflectors have been added for the same reason, while the wheels feature mobile shutters activated and controlled by centrifugal force.
The tires are tall and narrow 19-inch (155/70) Michelins with ultra low rolling resistance just like on Renault’s concept. The wheel arches also feature an air curtain, achieved with small aerodynamic slats on either end of the front bumper to channel the air along the wheels. The spoiler has been lengthened and an air extractor has been added on the rear bumper in order to reduce the turbulence that can increase drag. The underside of the car is streamlined.
As you can see, the door mirrors were also replaced by cameras, and while these are illegal in most countries at this point, that will have to change soon.
Unladen weight? 1,906 pounds/865 kg. This is the way forward.