First shown at the Paris and then Bologna and Geneva Motorshows, the Citroën C4 WRC Hybrid4 made its debut on the road in Finland before that country’s world rally car round in a slow speed demonstration. Subsequent testing in Faro, Portugal was the first at rally speeds and under rally conditions. The C4 Hybrid was developed using Citroën’s WRC championship contender as a base and adding a 400V, 22 Ah, 990-cell lithium-ion battery and a UQM Powerphase 125 electric propulsion system which drives the rear wheels.

This system, developed by Citroën Racing, allows the driver to choose between four different modes of functionality. In internal combustion mode, the C4 WRC Hybrid4 behaves exactly like one of the C4 WRC cars that compete on the World Rally Championship. In internal combustion mode, with energy recovery mode switched on, braking endurance is improved and the batteries get charged. On road sections and in the service park, electric mode with energy recovery means that there is less nuisance, increased range and less wear on the conventional engine. Finally, in boost mode—which employs both the internal combustion engine and the electric motor—gives an extra 300 Nm of torque when engaged.

—Didier Clement, race engineer

The combustion engine and electric motor are linked to the same drivetrain. The driver can choose electric mode simply by switching on the ignition without starting the internal combustion engine. The gearbox paddles then gives the driver a choice of three settings: forward, backwards and neutral.

The objective with this project was to be able to use the electric motor to drive on some of the road sections. This fully operational concept responds to that design brief. Citroën Racing wanted to show its ability to adapt this technology to motorsport. If at any point in the future the regulations permit the use of hybrid technology, we will be able to react straight away.

—Didier Raso, electrical and systems engineer