Citroen C4 Cactus Airflow 2L Concept: Unusual gas/air hybrid

Following up on the original soft-sided C4 Cactus production crossover it presented in Geneva earlier this year, Citroen has created a new C4 Cactus Airflow 2L Concept for Paris that combines unique aerodynamic tweaks, significant weight reduction and a bespoke version of PSA’s Hybrid Air Technology to achieve a claimed 117.6 U.S. mpg. That’s equivalent of 2.0 liters of gasoline per 100 kilometers – a 30 percent improvement over its already rather frugal volume-build C4 sibling. 

The Airflow 2L Concept’s achieves this efficiency through its unique Hybrid Air powertrain. First revealed by Citroen in 2013, it matches an 82-horsepower specially modified, low-friction PSA 1.2-liter/3-cylinder PureTech engine with a twin-tank compressed air storage unit and a hydraulic pump/motor that effectively replace the battery pack found in a traditional gas/electric hybrid. Instead of using an electric motor, it relies on compressed air to pump the pistons, which in turn drives the front wheels through a conventional automatic transmission. As a result, this compact crossover can run in three modes: on its engine, compressed air alone or a combination of the two.

Super-sleek and ultra-light

As its name implies, the Cactus Airflow 2L Concept boasts a host of wind-cheating changes. Sleeker basic body bits bring Air Curtain wheel-arch treatments, an extended rear spoiler, new rear extractor, a streamlined full underbody fairing and small cameras that replace the conventional side-view mirrors. These are complemented by several "variable geometry" components. Air inlets in the front bumper continuously adjust to optimize flow while the custom Michelin 19-inch ultra-low rolling resistance tires are wrapped around alloy wheels that feature active shutters and a movable deflector at the C-pillar further tidies the air going around the car. Citroen estimates these modifications cut drag by 20 percent relative to the baseline C4 Cactus.

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A second key to the Airflow 2L Concept’s efficiency is a 220-pound reduction in curb weight. At 1,907 pounds, it tips the scales 11 percent below the standard-issue Cactus. As expected, the savings come from leightweight materials. The core structure mixes high-strength steel, aluminum and various composites which are complemented by carbon-composite components in most of its body panels as well as in things like the Airflow 2L’s springs, rear seat and signature door-ding-protecting "side bumps". More weight savings result from the use of a polycarbonate panoramic roof panel.

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Citroen says the C4 Cactus Airflow 2L Concept illustrates "the ambition and ability of the brand to develop innovative responses to the automotive challenges of the present and the future." Key among those tasks will be to accommodate the French government’s request of the industry to create production cars that can meet the 2.0-liter/100 kilometer efficiency benchmark by 2020. 

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