Tony O'Kane | Apr 10, 2009

It looks like a rally car, it goes like a rally car but by George, you ain't seen anything like this before. This is Citroen's C4 WRC HYbrid4 rally car, and Citroen believes it will revolutionise the world of top-tier rallying.

Testing of the C4 HYbrid4 commenced this week in Portugal on tarmac roads near the town of Faro, with Citroen Racing's Dani Sordo behind the tiller. The Faro tests were the first real-world validation of the hybrid racer's capabilities, and Sordo was impressed with initial performance.

"On the stages, I would say that the overall behaviour of the car is slightly different to that of the C4 WRC, with more weight to the rear," Sordo said.

"[But] the feeling is on the whole the same as the one I have with the standard rally car, and I love the way that the C4 goes on asphalt!"

The C4 WRC HYbrid4 marries the regular WRC car's 223kW (300hp) petrol engine gearbox and AWD drivetrain with a 125kW/300Nm electric motor and 990­cell lithium-ion battery pack. Regenerative braking technology is also used to top up the batteries and improve braking performance.

Citroen C4 WRC HYbrid4

The motor and battery pack add an extra 150kg to the car's overall weight, but that's more than offset by the substantial boost in power that the electric motor delivers to the rear wheels. Plus with four modes of operation, the hybrid system makes the C4 HYbrid4 a much more versatile machine. Citroen Racing's Didier Clement explains:

"In internal combustion mode, the Citroën C4 WRC HYbrid4 behaves exactly like one of the C4 WRC cars that compete on the World Rally Championship," said Clement.

"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's the latter mode that has Dani Sordo most impressed, however.

"The boost function means that we can choose when to benefit from extra torque under acceleration. When it comes in, the effect is very impressive!"

While the hybrid system is just a technological showcase for now, Citroen Racing says it proves that hybrids definitely have a place in the world of rallysport.

"Citroën Racing wanted to show its ability to adapt this technology to motorsport," said Didier Raso, an electrical and systems engineer with Citroen Racing.

"If at any point in the future the regulations permit the use of hybrid technology, we will be able to react straight away."

PRESS RELEASE

Citroen Tests The World's First Hybrid World Rally Car

Citroen Racing have started testing its Citroen C4 WRC Hybrid World Rally Car, proving that its technological showcase is much more than just a motor show star and that it is paving the way for low consumption, low emission, low noise motor sport cars of the future.

Just hours after winning its four World Rally Championship event of the season, Citroen Racing took the new car testing in Portugal using tarmac roads near Faro with Citroen’s Spanish driver, Dani Sordo, behind the wheel

First seen 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 WRC round in a slow speed demonstration, but the Faro test was the first at rally speeds and under rally conditions.

The Citroën C4 WRC HYbrid4 was developed using Citroën’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 addition of a 990­cell Ion Lithium battery on top of the petrol tank and a 125 kW electric motor driving the rear wheels puts an extra 150 kg onto the overall weight.

“This system, developed by Citroën Racing, allows the driver to choose between four different modes of functionality,” explains Didier Clement, one of the race engineers behind the project. “In internal combustion mode, the Citroën 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 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.”

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, Citroën 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 life­sized context.

The second part of the test was a somewhat more familiar territory for Citroën 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.

Following the three challenging days of Rally Portugal, which resulted in a third place for Dani Sordo, the young Spaniard looked forward to his latest task with enthusiasm.

“In electric mode, you can drive through villages without making the slightest noise, which is very unusual for a competition car,” he reported during the hybrid car’s test. “It’s better for the environment and also more comfortable for the crew, making road sections more pleasant.”

Sordo’s comments on the car’s pure performance were equally complimentary.

“On the stages, I would say that the overall behaviour of the car is slightly different to that of the C4 WRC, with more weight to the rear,” he reported after his first few flying kilometres in internal combustion mode. “The boost function means that we can choose when to benefit from extra torque under acceleration. When it comes in, the effect is very impressive!”

Just as is the case on the C4 WRC, the car set­up and tyre choice allow the driver to fine­tune the handling.

“The feeling is on the whole the same as the one I have with the standard rally car,” added Sordo. “And I love the way that the C4 goes on asphalt!”

Throughout this test session, which well and truly underlined the creativity of Citroën Racing, the Citroën C4 WRC HYbrid4 demonstrated all the credentials that make it an important technological advance in rallying. Driving a C4 HYbrid4 that nonetheless has several things in common with his usual car, Dani Sordo successfully completed a fruitful test in which several valuable lessons were learned for the future.

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