Lexus has upgraded its hi-po IS F model with numerous changes to the interior -- plus a more significant change that, although it can't be seen, will most certainly be felt.
While it might be nice to know your new V8 Lexus sports sedan has improved USB functionality, folding rear head restraints, a revised satnav/air-conditioning fascia and rocker-tyre sunroof switches, serious drivers will be even more pleased about the replacement of the previous brake-actuated 'limited-slip' differential with a new mechanical Torsen LSD.
Formerly the IS F relied on rear-wheel brake application via the stability control system to direct torque to the side with better grip, but this drew criticism as being inadequate to control the 311kW 5.0-litre V8's power, particularly when cornering. The new torque-sensing Torsen LSD (Tor-Sen) does the job within the differential itself by applying torque progressively to the side where it can be better used.
The Torsen LSD detects side-to-side variants in torque and works to bind the gears on the side with better traction for more effective power delivery. A purely mechanical device, the Torsen differential is commonly used in 4WD applications.
Lexus claims adoption of the Torsen LSD makes a measurable difference to its ability to put power to the ground:
According to Lexus press material, the new Torsen-equipped IS F is two seconds a lap faster around the Fuji International Speedway where much of its development took place.
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