Latest in the line of RS models, the
Ford Focus RS gives the name a new twist, pushing the amount of power previously thought impractical through the front wheels only. Tested extensively round the Nurburgring, this new hot hatch is claimed to set new standards for high-performance hot hatches.
Before the advent of electronic aids, this would have meant excessive torque steer – as on the Mazda MPS – and far too much wheelspin. Nowadays, with conventional traction control, this means that the power never gets to the wheels, being shut down as soon as you get wheelspin, so having this much power is a waste of time.
Ford of Europe has used the RS name for its hottest cars over the years, but these were generally four-wheel drive. A hundred years ago, cost constraints led to Henry Ford saying you could have any color so long as it was black. Now, even more drastic cost constraints have made Ford's mantra: 'You can have any drive you like so long as it is front-wheel drive.' Yes, the rear-drive Aussie Fords will be the last rear-drive Fords, and four-wheel drive RS models are a thing of the past.
Had to be front-wheel drive only
Without four-wheel drive, Ford's RS engineers had to do something different – they weren't going to muffle the power with a traction control that reduced engine torque every time the car got wheelspin. So they found new solutions.
But first, they had to get the power, and make the car look right. And they certainly seem to have done a good job with the styling, which keeps Ford's new front end, but gives it a sporty twist, aided by the cooling vents, high wing, and fat twin exhaust pipes. Yes, the Focus RS looks the part.
It was that that difficult, really, to up the power, and the handling to suit, because they already had the 225 bhp five-cylinder engine of the Focus ST to start with. In fact, the ST is the basis for the the RS in many respects, and has excellent handling for a front-driver.
Hot camshaft, big turbo, more boost
To get more power, Ford engineers adopted a revised camshaft profile, beefed up the engine to suit, and then bolted on a larger turbo – except that this one is integrated into the exhaust manifold to reduce weight and improve efficiency.
The Borg Warner K16 turbo allows boost of 1.4 bar (20 psi) instead of the modest 0.7 bar (10 psi) of the ST, and that is the source of most of the extra power.
The intake system was also streamlined to reduce losses, and a lot of effort went into making the turbo give boost at all speeds. The result is 300 bhp at 6,500, which is 35% more than the Focus ST, with an impressive amount of torque, which was one of the strong points of the ST. The new engine produces 325 lb ft (440 Nm) torque at 2,300 – 4,500 rpm, which is a wide spread for such a high performance engine.
To suit sporty drivers, the engine runs up to 7,050 rpm, producing the same amount of power. However, if you try to hold the engine at 7,050 rpm, without shifting up, the controller brings you back to a reliable 6,500 rpm.
Not so hot as Audi's new five, though
So how does this engine compare with the best? Well, Audi has just introduced a five-cylinder 2.5 liter engine in the Audi TT RS, which not only manages 340 bhp, but also produces 330 lb ft (450Nm) all the way from 1,600 to 5,300 rpm.
Although the Focus RS engine is very good it is therefore just topped by Audi's latest, which has quattro four-wheel drive to get the power to the wheels. Four wheel drive and the extra power chops about 1.5 seconds off the 0-60 mph time, and maybe one second of that is the difference between front-wheel drive and four-wheel drive. True, the Audi is a much more expensive car.
Clever torque sensing diff to the rescue
In the Focus RS, power is transmitted through a six-speed manual box to a Quaife torque-sensing limited slip differential – the sort that has been used by Noble on its supercars for years, but in more refined form. This is a mechanical device, which senses the amount of torque being transmitted to each wheel and progressively shifts the torque to the wheel with most grip.
This design prevents the car suddenly running out of power with other methods, or suddenly shooting straight ahead, when you want to turn out of a T-junction on a wet road.
New suspension needed
But that was enough to tame this monster. Because wider wheels and tires were needed – and they are not as wide as you might expect – that pushed the central axis of the tires too far away from the strut, which was designed for cars with narrower wheels and less power.
To tame the inevitable torque steer that would have resulted with conventional struts, the engineers – who had done similar things for Ford's Rally cars -grafted a knuckle or hub carrier onto the strut. The knuckle is actually very similar to that of double wishbone suspension, except that it is not connected to the strut by ball-joints but by a pair of bushes.
This RevoKnuckle, as Ford calls it, similar to the system used by Renaultsport on the high-performance Meganes and Clios, but has several essential differences which enabled Ford to patent it. (See explanation in box below)
For the brakes, 13.2 in (336mm) diameter ventilated front discs are used, with 11.9 inch (302mm) solid rear discs – not that big by modern standards. There is the usual ABS, and a special stability control designed to enable the driver to get the most out of the car – not so with the ST, where it is best to turn it off when you want to drive the car fast.
Springs 40% stiffer than on Focus ST
To improve handling and reduce roll, the springs are 40% stiffer than on the ST – that it is a lot, bearing in mind that the ST is a sporty version – and the car sits 0.80 in (20 mm) lower on its suspension. The rear suspension is the 'control blade' wishbone suspension.
Continental developed some special tires to get this power on the road, these being 235/35/R19 tires - not that wide - on fat 19 by 8.5 inch rims.
So there it is: a 300 bhp front-driver hot hatch with that power actually being available, and without some of the vices we might expect from a front-driver.
However, all this refinement has come at a price in weight – the RS weighs in at over 200 lb (100 kg) more than the ST. Still, the weight is fairly competitive.
How hot is this hatch? A 0-60 mph time of 5.9 seconds is not that good, beating the 260 bhp Mazda 3 MPS by only 0.1 seconds, and not getting anywhere near the performance available with four-wheel drive. On the other hand, the now-superseded Mazda does have very strong torque steer which spoils the plot.
The Focus RS is an impressive newcomer, taking into account the constraints on the design, and no doubt the mid-range acceleration will be stunning.
With the knuckle buried in the wheel, this design separates the steering geometry completely from the strut movement. This gives much reduced offset between the steering axis and the central axis of the wheel, which was necessary to reduce torque steer. 