PSA Peugeot Citroën ingenious hybrid system, known as Hybrid Air, is proving so expensive to develop that the group needs partners to help, the firm's research and development boss Gilles Le Borgne has said.

Hybrid Air compresses gas on the overrun and turns it to propulsion when the car next accelerates or climbs a hill. Autocar UK has already driven a prototype Peugeot 2008 fitted with the system, while Peugeot showed a 208 fitted with the technology at the recent Paris motor show (below).

Citroen has also fitted a Hybrid Air-based powertrain to its C4 Cactus, creating the C4 Cactus Airflow 2L concept.

The system delivers real-world savings in fuel consumption and CO2 emissions of about 30 per cent. However, it requires a production run of about 500,000 cars a year to be economic, said Le Borgne, because the system needs quite a lot of components not currently found in cars – including hydraulic motors, special gearboxes and 300-bar gas tanks.

“Car companies are like big ships,” he said. “It takes time for them to change course as much as they could have to.”

Through component supply group Bosch, PSA is searching for suitable partners, but seemed disappointed by the slow response. “Hybrid Air is ready for development,” said Le Borgne, “but it needs a big investment and we are not ready to make it on our own.