ALL-NEW FORD FOCUS RS WRC 06: TECHNOLOGY AND INTELLIGENT SOLUTIONS
Here are the key technical elements of the new Ford Focus RS WRC 06, along with Christian Loriaux's thoughts on the solutions that he and his team of engineers developed:
Engine
Although the Focus ST model on which the World Rally Car is based uses a 2.5-litre, five-cylinder engine, rallying rules do not permit an engine of that size. However, the regulations do allow teams to use another engine from elsewhere in the Ford Focus model range, so M-Sport opted for the 2.0-litre Duratec unit, with the addition of a turbocharger and the mandatory 34mm inlet restrictor. French engine specialist Pipo Moteur was employed to assist with the initial development of the new unit. M-Sport also used its own in-house transient dynamometer and made use of data from Ford TeamRS to fine-tune the specification. One advantage over the outgoing rally car is that the new engine has an all-alloy block. This allows for a reduction in weight and also a transfer of weight away from a relatively high position, thereby helping to lower the car's centre of gravity. "We worked closely with Pipo to come up with a design," said Loriaux, "but once the first version of the engine arrived we put it straight onto our own dyno and completed more tests. After that, and more discussions, we changed the design of the crankshaft."
Suspension
The new Focus RS WRC 06's suspension is a further development of the type used on the 2004-specification car, although rule changes forced M-Sport's engineers to make revisions.
To help reduce costs in world rallying, the use of expensive materials such as titanium is now severely restricted, and Ford's engineers had to find a substitute that was strong without adding too much weight. The suspension continues to use Reiger dampers. Representatives from the Dutch firm liaised with Loriaux and his staff during the design phase, and were also present during the first few kilometres of testing to help with the initial set-up. "Under WRC rules there are such tight restrictions on the amount of power that the engine can produce that elements like the suspension have become even more important," said Loriaux. "We worked hard to strike a balance between handling and traction." Suspension parts were tested on a 2004-specification Focus RS WRC in rough conditions before the design was finalised.
Transmission
M-Sport's transmission consultant Ricardo played a key role in the development of the new car, since the new rules forbid the use of computer-controlled front and rear differentials. Instead, only the centre differential features this level of technology, with regular mechanical units at the front and rear. The fact that more of the system is now beyond computer control has only heightened the importance of arriving at a robust initial set-up. "Some of the restrictions on materials affected this side of the design too," said Loriaux. "The propshaft is now steel, for example. But that means it has to be slightly wider to retain strength, so the transmission tunnel had to be made slightly larger to accommodate it."
Bodyshell
The new Ford Focus RS WRC 06 is based on the Focus ST road car. It is larger than its predecessor, presenting engineers with the challenge of keeping overall weight increase to a minimum. In addition, the new car's width is 1800mm, the precise maximum specified under World Rally Car regulations.
"We liaised closely with Ford TeamRS on the shell," said Loriaux. "We used the ADAMS software model to help with our initial design and that allowed us to experiment with the car's layout and see how changes to one specific component might affect the other parts. We also worked hard on the aerodynamic side, because the new car has a larger frontal area. We tried to compensate for this as much as possible and to reduce drag on faster sections. On the other hand, the more steeply-sloped rear hatch of the new car plays back into our hands, in terms of making the rear wing more efficient."
Gearbox
The Ford Focus RS WRC 06 features a considerable amount of change in its gearbox from the previous model, not only in specification but also in layout. The original Focus WRC (introduced in 1999) mated a longitudinal gearbox to a transverse engine, an engineering feat in itself. But for the new car, Loriaux decided to use a transverse gearbox along with the transverse engine. "I think there are benefits in packaging but also there should be less loss through friction," he said. The new Ricardo-developed gearbox will have five gears, not six like the outgoing model. "Reducing the number of gears allows us to make a small weight saving and also a saving in terms of size of the gearbox itself," said Loriaux. "We think that with the 34mm air restrictor on the turbocharger, as specified by the rules, the engine's low-down strength and torque mean a five-speed unit will be as effective as a six-speed one. After all, with six speeds you do lose a little more time through more frequent changes anyway."
Weight distribution
Loriaux is renowned for his innovative design approach to lowering the centre of gravity in rally machinery. Many of the trends seen on today's cars, such as the crew sitting particularly low in the cabin, can be attributed to Loriaux's earlier designs. From the earliest drawings of this new car, he has again been determined to set new trends.
"A low centre of gravity helps with handling, balance and steering feedback," said Loriaux. "We've tried to make the engine as low as possible and with no compromises in the layout, to help achieve that." Some of the more radical solutions will remain secret, but no element of the car's layout or design has escaped intense scrutiny as far as weight distribution is concerned.
