‘Twinster’ allows Ford’s hot hatch to chart a different route
WHAT MAKES THE FOCUS’S ALL-WHEEL-DRIVE system different is that, when drive to the rear is engaged, a small difference in gearing between the front and rear axles (less than two per cent) overspeeds the rear wheels. They turn a little faster, loading the rear and giving a rear-drive feel.
The key part in all this is the GKN ‘Twinster’ device that takes the place of the rear differential. The propshaft to it is always spinning, but the Twinster is only engaged when required, at which point its twin wet clutch packs – one for each rear wheel – are activated. In steady-state running they are open, disconnecting the drive to the rear wheels, aiding economy but also essential because the difference in gearing would constantly try to rotate the rear wheels faster than the fronts.
The Twinster also delivers one of the holy grails of drivetrain function: pure torque vectoring. The electronically controlled, hydraulically activated clutch packs send the appropriate torque independently to each rear wheel based on inputs such as steering wheel angle, lateral acceleration, yaw and speed. The moment the system senses rear-drive can help, torque is sent to the outer rear wheel. This speeds it up, rotating the Focus into the turn. Up to 100 per cent of the torque available at the rear can be sent to one wheel.
Electronic stability control systems typically manipulate a car’s balance by braking individual wheels, whereas the Focus’s system is enabling rather than restricting, adding positive torque rather than braking force. The degree of torque delivered to the rear wheels, and thus the attitude created, depends on the selected drive mode, from neutrality in Normal, to appreciably rear-drive in Track, and ultimately generous power oversteer in Drift.
Engine In-line 4-cyl, 2261cc, turbo Power 345bhp @ 6000rpm Torque 347lb ft @ 2000-4500rpm 0-62mph 4.7sec (claimed) Top speed 166mph (claimed) Weight 1547kg (227bhp/ton) Basic price £32,765 evo rating