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Citroën to show Cactus concept with Hybrid Air powertrain

Citroën Cactus concept with Airbumps (not related to the Hybrid Air powertrain). Click to enlarge.

At the upcoming Frankfurt Motor Show, Citroën will showcase its Cactus C-segment concept car, featuring, among other technologies, the Hybrid Air powertrain co-developed by PSA Peugeot Citroën and Bosch. (Earlier post.)

Hybrid Air is a full-hybrid solution combining compressed air and hydraulic power, with no battery required for energy storage. Hybrid Air combines a PureTech gasoline engine, a compressed air energy storage unit, a hydraulic pump/motor unit and an automatic transmission with an epicyclic gear train.

An intelligent electronic management system manages input from the driver to optimise energy efficiency. Three operating modes are available:

  • Air power, with zero emissions. The energy stored (compressed air) is transmitted to the wheels via the hydraulic motors and gearbox. Depending on traffic, this mode will concern between 60 and 80% of urban driving time. Maximum use of deceleration and braking energy will ensure efficient recharging of the compressed air unit. This mode is active up to 70 km/h (43 mph).

  • Gasoline power. Gasoline mode transmits energy to the wheels without input from the compressed air unit. This mode is used primarily outside urban areas. Here again, the energy from deceleration and braking is recovered for the rapid benefit of ZEV/air mode or the boost function in combined mode.

  • Combined power, with the combustion engine and hydraulic motor working together. This mode is used particularly during pick-up and strong acceleration, with a significant boost effect (total power of up to 90 kW) delivering a performance comparable to that of an engine in the next segment up.

At the Geneva Motor Show, Citroën showed a C3 prototype fitted with the Air Hybrid system that offered fuel consumption of 2.9 l/100 km (81 mpgUS) (69 g of CO2/km). (Earlier post.) PSA has already said Hybrid Air technology will be fitted on B-segment models starting in 2016.

Applied in the Cactus, the Hybrid Air system delivers fuel consumption of under 3 l/100 km (78 mpgUS), and features a 45% reduction in fuel consumption in urban driving.

Airbumps. Located on the sides and the bumpers of the car, the design component expresses a new approach that gives style a function. The supple skin of the Airbump features a soft treatment that resists scratches and includes air capsules that dampen impact.

The Cactus, which reaches back to the reveal of the C-Cactus concept car at the 2007 Frankfurt show, previews forthcoming models in its C line, Citroën said, with more to be revealed in 2014.



I favored compressed air expanded using engine heat, but the numbers did not work. It cost too much and produced to little.


Increased mechanical complexity, even over a regular ICEV, will make this unit a repair shop dream?

A light weight BEV, with 5-5-5 battery pack, could be a much simpler machine to build, operate and maintain?


Most of the trouble with cars is related to the electrical system. Why would anyone who praises reliability want more of it?


SJC, why wouldn't it work?  The engine itself works on the expansion of "heated compressed air".  I would like to see your analysis, if you have it in a format you can post.

Bottoming-cycle engines like BMW's "turbosteamer" stay in the news.  It's only a matter of time until they start showing up in the market.

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