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Wednesday 13th February 2013


GIVING US THE SLIP

Why carmakers are banishing the electronic nannies to the back seat


Amazing to think it, but performance car brands are finding the courage and the tech to let us explore the limits of grip. You'd think the western world's daily worship at the altar of health and safety would have denied the average driver any exploration of the limits in new performance cars. Incredibly, that's not the case.

Ford says there is the freedom to include slip
Ford says there is the freedom to include slip
Increasingly clever electronics and a refreshing change of attitude to what performance means has led more makers to allow us to safely experience grip loss if we go looking for it.

Case in point, Ford. "We try and get the fun-to-drive factor, which means the driver can destabilise the car if he wants," Len Urwin, powertrain engineering manager at Ford's Team RS, told us. "10 years ago, you couldn't do lift-off oversteer in a Ford because it was construed as being not want the customer wanted. It was seen as unsafe, but these days for performance cars, to a degree it's encouraged."

It was a statement that gladdened our hearts and got us looking for more examples of this liberated attitude. The glaring one is the Toyota GT86.

So, are carmakers going to let us do this?
So, are carmakers going to let us do this?
Toyota has made little secret of the tail-out simplicity of its back to basics sports car, even designing the badge to resemble four drifting wheels within the number 86, or so it says. Fitting a sweet-handling rear-drive car with torque sensing limited-slip diff and three modes of stability control is just about the perfect recipe on paper to safely explore grip.

"Discreet safety net"
Elsewhere Porsche is subtlety promoting tail out action in its new Cayman, pointing out that the PDK twin-clutch gearbox "permits a dynamic driving style" by figuring out the driver is drifting and holding onto gears when the stablilty control is switched off, "assuming a suitably protected roadway".

Latest tech exploited to the max on Cayman
Latest tech exploited to the max on Cayman
Jaguar is another. With similar coyness to Porsche, it says that the Trac DSC setting of its stability control in the new XFR-S "offers the enthusiastic driver more opportunity to explore the outer edges of the handling envelope" while providing "a discreet safety net."

Of course, in the old days, loss of grip threatened whether you went looking for it or not. But for the enthusiast driving right on the edge of grip on road or track was infinitely rewarding, not least because it was usually telegraphed so clearly.

"If the grip started to go you could really feel it," celebrated Jaguar test driver Norman Dewis told us recently. "If you look at these cars today, the grip they've got ... These really wide tyres really glue them to the road."

Jaguar is a big fan of feel and feedback
Jaguar is a big fan of feel and feedback
The breakdown in communications from road to driver continues with all the technology feeding more pressing demands, such as comfort, safety and emissions. But hearteningly technology can also be the enthusiast driver's friend. Case in point, the brilliant stability control Lotus has applied to its new Exige S.

The Lotus race setting
The beautifully balanced V6 two-seater has a version of Lotus's Dynamic Performance Management co-created with Bosch that now offers four different levels of assistance, with the addition of a Race setting just above 'off'. Lotus calls it an 'enhancement' to its traditionalhandling purity.

"We want the car to be able to communicate to the driver, give them enough feedback so they can feel the limit of that grip, and when they reach it, that's when our stability system comes in," principal vehicle dynamics engineer Alan Clark tells PistonHeads.

Lotus's nifty new stability control on the Exige S
Lotus's nifty new stability control on the Exige S
Stability control prevents slides, unwanted or not, by braking individual wheels and reducing engine torque, and is often regarded with disdain by keener drivers for its obvious intrusion. But smarter systems like the Lotus DPM can delicately adjust the help it needs, with Race presenting what Lotus reckons is the perfect level of assistance for the fastest track lap. And, like Jaguar's "discreet safety net" it'll tidy up the larier slides.

"It comes to the point of a certain yaw angle and we say, okay, we need to act here and help the driver out," says Clark.

You'd think the EU would step in this point and wave the red flag, and to an extent it does. From this year all new cars sold in Europe have to be fitted with stability control, but the rules also allow the system to be switched off, providing a light indicates that fact and that when you start the car next time, it reverts to the stability 'on' setting. It's a measure of how discreet Lotus's Race setting is that the EU requires it to trigger the 'off' dash light...

BMW's GKN-supplied diff enables lots of this
BMW's GKN-supplied diff enables lots of this
BMW's "constant drift"
It's not the Lotus way, but a limited-slip diff is often touted as the perfect ingredient to for fast, tail-dancing driving, especially a torque-sensing LSD such as that in the GT86.

"You can steer the car by sliding on the throttle, which many people like," says Heinrich Huchtkoetter, senior engineer for drivetrain engineering firm GKN.
The British firm makes the Visco LokLSDs fitted to the last generation BMW M cars, and Huchkoetter reveals that the M division has long wanted its cars to be driftable. He says, "When BMW first approached us, they asked: 'can do you a limited-slip differential which enables a driver who can do it to keep the vehicle in a constant drift?'"

Drivers found it tricky to balance though, and our engineering insider explains that's because the speed sensing Visco Lok will only lock up when it detects a spinning wheel. "There is a delay, so you had to give more throttle to speed up."

Mid-way 'hero' modes are now commonplace
Mid-way 'hero' modes are now commonplace
High tech hooning
But again we've got technology to help us out. The M5, M6 and forthcoming M3 come with the so-called Active Mdifferential, also made by GKN. The independent control of each driveshaft this gives has a wealth of advantages, including drifting. "You can close the LSD even before the inner wheel is spinning, then you get it more or less controlled by the throttle into a drift immediately," Huchkoetter tells us.

This tech is spreading too. Jaguar's active electronic differential on the XFR-S and the top-spec F-Type is the same system, made by GKN. It can apply "full locking torque almost instantaneously" says Jaguar - ideal for a tail wag.

Even Lotus, not a fan of passive LSDs, is keen. "An active diff would be a better compromise than a mechanical limited-slip diff," says Clark. Plotting one on the new Esprit maybe...?

Exige S is faster with DPM in race mode
Exige S is faster with DPM in race mode
But then the attitude at Lotus is a reminder that purist drivers have a racer's disdain for lurid slides. Says Clark of the DPM stability system, "It'll only kick in if you've made a mistake."

Author: NickGibbs