29/1/12

Overview: Toyota Land Cruiser V8

Toyota’s biggest Land-Cruiser has been revised for 2012, with changes to the power-unit and a variety of new and upgraded driver-assistance systems.

The Land Cruiser’s twin-turbocharged 4461cc diesel has gained new injectors and a particulate filter to bring it up to EU5 emissions standards — a trifle tardily. A device called Turn Assist — no details are available yet — reduces the vehicle’s turning radius when driving through tight off-road bends, and the existing Crawl Control now has five speed settings for tackling steep climbs or descents.

The variable assistance of the power steering system now has an off-road setting. A new terrain monitor uses four external cameras to provide a 360-degree view of the area immediately around the vehicle, while Multi-terrain Select offers five selectable driving modes to tailor the car’s behaviour to different off-road conditions.

Background

The Land Cruiser V8’s dimensions and specification place it a little behind the Range Rover in most key measures, with one interesting exception: it has a much better wading depth, perhaps a mark of superior door seals.

Power is supplied by a twin-turbocharged 4461cc V8 diesel, its twin fuel rails running at a maximum of 180MPa. Changes to bring the unit in line with Euro 5 emissions standards have seen 12PS disappear from the maximum power available, but it still peaks at a very gentlemanly 3600rpm and maximum torque has not been affected. Toyota boasts that the engine will run ‘faultlessly’ at -30°C. The blowers are low-inertia units with variable nozzle geometry; the nozzle size is controlled by a 12V DC electric motor.

The V8’s engine block (like the Range Rover’s) is cast in compacted graphite cast iron (CGI). An oil scavenging system fitted to the turbochargers to collect surplus oil and reduce blue smoke emission when driving on an incline, turning or braking. Two electronically-controlled hydraulic engine-mounts are used.

The exhaust gas recirculation (EGR) system is water-cooled using a multi-layered EGR cooler. The EGR gas passages have been incorporated into the cylinder head to reduce the complexity of parts and the all-up mass of the engine instalation. Two rotary solenoid diesel throttles and linear solenoid EGR valves are used to cut the level of visible smoke and avoid unstable combustion.

Drive torque is directed to all four wheels permanently by way of a six-speed automatic transmission driving through a Torsen centre differential unit. In fully automatic mode, the gearbox uses ‘artificial intelligence’ shift control, to modify the shift pattern according to how and on what type of surface the car is being driven. This can take account, for example, of up- or down-hill driving. The transmission also features a deceleration downshift which helps slow the vehicle; it also provides a fuel cut-off control.

In normal dry-road driving, torque distribution is 40/60 front to rear. However, the Torsen unit can send up to 50 per cent. of the torque to the front wheels and up to 70 per cent. to the back.

The Land Cruiser uses a body-on-frame construction. There is high tensile steel in the chassis, though Toyota isn’t saying what proportion. Hydro-forming is used for some of the cross-members: this affects the strength of the wlded joints between the cross-member and the side-rail as well as that of the members themselves. The frame’s torsional rigidity is claimed to be 1.4 times greater than that of the outgoing Land Cruiser Amazon, with flexural rigidity 1.2 times better. An extra lightweight front suspension cross member has been added, and the coil support area of the front suspension has been strengthened. High-tensile steel is used ‘extensively’ throughout the body.

At the front, coil springs replace the Amazon’s torsion bar, with claimed benefits to ride comfort and wheel control. The suspension has a double-wishbone layout with inclined coil springs and dampers. The front wheel stroke has been increased by 11 per cent. for load and 18 per cent. for rebound, now totalling 230mm; rear wheel travel remains at 240mm. The four-link coil-sprung rear suspension from the Amazon is carried over to the V8, with some retuning to improve handling, ride comfort and off-road performance. Roll-steer has been tuned by moving the control arm.

Spring rate control operates on the front suspension, using a single control valve to adjust the suspension characteristics when turning or braking. This means that the front suspension can be stiffened to reduce roll or pitch angle during high-speed manoeuvres, but softened in normal driving.

A mechanical system functions as a link between the four wheels. On the road, the balanced pressure across all four wheels provides normal car-like behaviour; but off-road, the movement of wheels out of phase with each other allows the hydraulic pressure to vary and releases the individual wheels, increasing wheel articulation.

Variable gear ratio steering is used, with the ratio set higher around the straight-ahead position.

Active Height Control (AHC) functions have been improved to extend the range of height adjustment and shorten the time it takes to lower the car. The front of the Land Cruiser V8 now has 110mm of height adjustment, with 100mm available at the rear. Shifting from normal to low mode takes about two seconds. The ride height is automatically raised when low range is selected in the transfer gearbox, and it is increased by a further 20mm when the system recognises that the vehicle is stuck. It automatically lowers the vehicle to improve stability when driving at high speeds.

The multi-terrain ABS incorporates a control logic that recognises any road surface and automatically switches to the appropriate braking control. Using information such as engine output, acceleration rate and wheel speed, the on-board computer can sense off-road driving, such as snow, dirt and sand. It then controls the ABS using a slip rate programmed for that type of surface.

Electronic Brake-force Distribution (EBD) and Brake Assist (BA) are fitted, detecting emergency braking and automatically boosting the braking force if the system decides that the driver has been a little over-delicate with the pedal.

Vehicle Stability Control (VSC) intervenes when sensors detect the Land Cruiser V8 is reaching the limits of its cornering ability. The system has been upgraded to include a cut-off switch: this enables the driver to deactivate VSC and traction control, preventing it from automatically reducing engine output when using high wheel-spin to escape from mud, fresh snow or other difficult terrain. Another development is that the Active Traction Control (A-TRC) now maximises traction and vehicle speed without the operation of a differential lock when the vehicle is in low-ratio four-wheel drive mode (L4). When L4 is selected, the engine output control is lifted, but the braking system receives stronger hydraulic pressure control. A-TRC works in combination with a number of other traction control devices such as the Hill-start Assist Control (HAC).

The Land Cruiser V8’s Crawl Control system replaced the previous Downhill Assist Control (DAC). It automatically controls engine output and brake hydraulic pressure to maintain off-road driving stability at a steady (low) speed. By activating Crawl Control, the less experienced off-road driver can concentrate on steering the car, as the accelerator and brake are automatically governed by the system. For the 2012 model year, the number of speed setting was increased from three to five.

Hill-start Assist Control allows an easier start when setting off from a steep or low-grip hill position by automatically controlling the brake as the driver moves from brake to accelerator, reducing backward motion. By controlling the rotation of each individual wheel, HAC is able to hold the car, allowing the driver to pull away without losing control.

Inside, eight airbags are fitted, including front knee airbags and curtain shield airbags along the entire length of the cabin. Both front seats feature Whiplash Injury Lessening (WIL) technology, which reduces the effect on an occupant’s neck of a rear collision. An active head-restraint structure senses movement in the lower back-rest and pushes the head-restraint upwards by 30mm and forwards by 25mm to reduce neck movement and, thus, the risk of whiplash.

Toyota
Land Cruiser V8
Range Rover
TD V8
Length 4950 4972
Width 1970 1956
Height 1865 1865
Wheelbase 2850 2880
Turning circle 11.8m 12.6m
Approach (deg) 31 34
Departure (deg) 23 26
Ramp breakover (deg) 24 25/30
Wading depth 700 500
Cd 0.35 0.38
Kerb mass 2555 2635
Towing limit 3500 3500
Fuel tank (l) 93 97
Cylinders 8V 8V
Valves 4 4
Block/head CGI/Al CGI/Al
Swept volume 4461cc 4367cc
Bore/stroke 86.0/96.0 84.0/98.5
Compression ratio 16.8:1 16.1:1
Aspiration 2T 2T
Injection pressure 180MPa 200MPa
PS/rpm 272/3600 313/4000
Nm/rpm 650/1600 700/1500
Maximum speed 130 130
0-100km/h 8.2s 7.8s
Transmission A6 A8
Driven wheels All All
Urban MPG
(l/100km)
23.5
(12.0)
24.6
(11.5)
Combined MPG
(l/100km)
27.7
(10.2)
30.1
(9.4)
CO2 g/km 270 253
Emissions EU5 EU5
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