Friday, August 17, 2012

Jaguar introduces AWD for XF and XJ; V6, 8-speed transmission and stop/start


Jaguar is introducing a new All-Wheel Drive (AWD) system to its 2013 Model Year XF and XJ saloon cars for selected markets powered exclusively by a new 340PS (335 hp, 250 kW) 3.0-liter V6 supercharged gasoline engine, a ZF eight-speed automatic transmission, and Stop/Start technology.
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Jaguar AWD. Click to enlarge.
Jaguar AWD operates intelligently, continuously monitoring grip levels and driver inputs to both pre-empt and react to wheel-slip, enabling maximum traction in all conditions.
Feed-forward torque distribution allows the system to actively anticipate wheel slippage and prevent it occurring, therefore providing greater driver confidence and vehicle stability in low-grip scenarios. Torque split can be up to 50:50 front/rear. At speed in normal grip conditions the AWD system is rear-wheel drive-biased.
The longitudinal engine installation means Jaguar’s engineers were able to retain the rear axle as the primary drive path, with a multiplate clutch within the transfer case apportioning torque to the front axle as dictated by grip conditions and driver inputs.
Providing the power for the All-Wheel Drive system is Jaguar’s new all-aluminium 3.0 V6 S/C 340 gasoline engine, which delivers 450 N·m (332 lb-ft) peak torque output produced from 3500-5000 rpm, with 400 N·m (295 lb-ft) available from just over 2000rpm for low-down pulling power.
The 3.0 V6 S/C 340 utilizes dual independent variable cam timing (DIVCT) and spray-guided direct injection (SGDI), allied to new spark plug orientation that aligns the electrode precisely within the combustion chamber for enhanced efficiency. These features, along with a compression ratio of 10.5:1, optimize power, torque and economy throughout the rev range.
The latest twin-vortex Roots-type supercharger is mounted in the V of the engine and features electronically managed boost control which offers operating efficiencies of up to 20%. A system of counter-rotating front and rear balancer weights devised by Jaguar’s engineers ensure the V6’s refinement matches that of the marque’s 5.0-liter gasoline V8s.
Utilizing a twin solenoid starter, the Jaguar Intelligent Stop/Start system is able to restart the engine in less time than it takes for the driver’s foot to move from the brake to the accelerator.
The All-Wheel Drive system utilizes the eight-speed automatic gearbox, standard on all XF and XJ models for the 2013 Model Year, but modified to accept the fitment of a transfer case with an active coupling which directs torque to a new front propshaft, front differential and halfshafts as required.
The multiplate wet clutch coupling directs torque through the front propshaft as dictated by the Transfer Case Control Module (TCCM), which monitors grip levels and driver inputs, apportioning the torque front and rear as appropriate.
In order to accommodate this All-Wheel Drive hardware in both the XF and XJ, a new front subframe, cross member, engine mounts and exhaust system have been engineered. The system has been optimally packaged with the front driveshafts running through the engine sump for a lower centre of gravity. The engine itself receives a recalibrated ECU to allow it to communicate with the active transfer case while under-bonnet modifications have been carried out to the fuel lines, hoses, air intake and exhaust to accept the new systems. A new engine undertray and heatshield incorporates a transmission tunnel acoustic pack to ensure refinement is identical to the rear-wheel drive models.
In dry road conditions, the All-Wheel Drive system operates in such a manner that all the dynamic qualities of the rear-wheel drive models are preserved by prioritizing torque delivery to the rear axle. The exception to this is on pull-away from rest when a pre-load torque is always applied to the front wheels to ensure smooth initial acceleration.
This is governed by the feed-forward element of the control algorithms, whereby situations in which wheel-slip might occur are predicted and accounted for by delivering torque to the front wheels as a pre-emptive measure to eliminate the possibility of a loss of grip. Because it is an active, rather than passive, torque delivery method, feed-forward allows the car to offer all-wheel drive security entirely unobtrusively while retaining dynamic rear-wheel drive handling characteristics.
The system constantly monitors road conditions, throttle and steering inputs and should any slip be detected between the front and rear axles, the TCCM will automatically apply reactive feed-back torque to negate any difference in front and rear wheel speeds. The maximum torque split is 50:50 front to rear.
When operating in Winter mode—selected by using the Jaguar Drive Control buttons—the feed-forward function is strengthened to pre-empt the possibility of wheel-spin. In addition, the Dynamic Stability Control system constantly monitors wheel-slip across each axle and uses the anti-lock braking system to selectively brake each of the four wheels as necessary to prevent wheel-spin.
Jaguar Drive Control also offers the driver the option of Dynamic mode in which throttle response is sharpened and the gearbox is instructed to upshift more quickly and at higher revs. Dynamic mode also firms up the damper settings in vehicles equipped with Adaptive Dynamics to deliver more precise, controlled body movements to enhance handling. In Dynamic mode, the All-Wheel Drive system operates in the same manner as in Normal mode.
Combined cycle fuel consumption is 9.8L/100km, equivalent to 234 g CO2/km.


Source: Green Car Congress

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