Citroen tests C4 WRC HYbrid4 Concept

10 April, 2009 02:43:00

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The day after the fourth round of this yearâ€™s WRC season in Portugal, which was won by the C4 WRC, Citroen Racing did some testing with the Citroen C4 WRC HYbrid4 concept car on an asphalt road close to Faro.

The C4 WRC HYbrid4 was unveiled at the Paris Motor Show last October. The concept went on to make a hit at the Bologna Motor Show and then at the opening ceremony of the Rally Norway. Since the Geneva Motor Show, it carries the new livery of the title-winning Citroen C4 WRC.

The Citroen C4 WRC HYbrid4 was developed using Citroen’s current World Rally Championship contender as a base. An electrical propulsion system has been added to the internal combustion engine, gearbox, and transmission that are specific to the WRC machine.

The car features a 990-cell lithium ion battery and a 125kW electric motor in addition to its usual petrol engine. The electric motor driving the rear wheels puts an extra 150 kg onto the overall weight.

This system, developed by Citroen Racing, allows the driver to choose between four different modes of functionality. In internal combustion mode with energy recovery 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, boost mode – which employs both the internal combustion engine and the electric motor – gives an extra 300 Nm of torque when engaged.

It can function in normal internal combustion mode, or can recover energy under braking to use as a boost via the electric engine when additional torque is required. Citroen has also designed the electric mode to be used on road sections between stages.

The two engines 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 give him a choice of three settings: forwards, backwards and neutral.

Didier Raso, an electrical and systems engineer, comments: “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.”

During the test session, Citroen Total World Rally Team driver Dani Sordo was able to evaluate the dynamic properties of the C4 WRC HYbrid4. One of the highlights of the day was a road section that passed through the village of Barranco do Velho, which was of course open to normal traffic. This allowed the team to assess the advantages of zero emissions in a life-sized context.

The second part of the test was a somewhat more familiar territory for Citroen Racing’s development team: a narrow and twisty asphalt road, not at all dissimilar to many of the demanding stages seen on the World Rally Championship.

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