Tuesday, March 25, 2008

The New Renault Laguna

Four-wheel steering for an exceptional ride

The Active Drive chassis with four-wheel steering brings many benefits, starting with improved manoeuvrability, extremely rigorous dynamic response, and unequalled steering precision which gives the driver truly intuitive control over the cornering line, to attain new heights in driveability and active safety. The steering is immediately reassuring and agreeable, even at low speeds. In town and on winding roads, the car is easy to drive: manoeuvrable and precise.

Advanced roll control, with specific settings and reinforced seat support, gives the impression that Renault Laguna GT corners flat, without leaning into the bend. The driver is pleasantly surprised by the lack of transient dynamic phenomena when cornering, and by the extreme precision achieved by very small steering wheel angles. The Active Drive chassis with four-wheel steering also excels in active safety, both under difficult braking conditions (with good control over asymmetrical grip, and ESP matched to sporty driving styles), and during avoidance manoeuvres at speed ('elk' test).

Impressive low-speed manoeuvrability

The Active Drive chassis with four-wheel steering makes Renault Laguna GT exceptionally easy to handle in town and superbly agile on winding roads. At speeds of less than 60kphh, the rear wheels turn in the opposite direction to the front wheels, up to an angle of 3.5°. This brings two advantages: a smaller turning circle, for easy manoeuvring; and smaller steering wheel angles thanks to the more direct, specially calibrated steering.

With four-wheel steering on the Active Drive chassis, Renault Laguna GT has a 10 per cent smaller turning circle than with two-wheel steering: 10.80 metres (the same as Clio!) with 18- inch tyres, instead of 12.05m. The greater the rear-wheel steering angle, the smaller the turning circle. Enhanced manoeuvrability is especially remarkable in tight parking situations and along narrow city streets.

With front wheels and rear wheels turning in opposite directions, the car effectively pivots, which means smaller steering angles are needed for the same turning effect. Whereas it takes a 16° steering wheel angle to produce a 1° turn in the front wheels on New Laguna, it takes just 13.5° with the Active Drive chassis. And this drops to 12° when the rear wheels are turned at the maximum 3.5° angle in the opposite direction to the front wheels. Because steering is more direct, with less need for wide steering wheel angles, the impression of manoeuvrability and agility is greatly enhanced. For any given bend profile, the driver will need less action on the steering wheel. This makes for more effective avoidance, with the car seeming to weave effortlessly around obstacles.

Ultra-precise steering control

From 60kph, the emphasis is on steering precision. The rear wheels turn simultaneously in the same direction as the front wheels, to enhance stability, almost as if the car were running on rails. The Active Drive system with four-wheel steering counters the centrifugal force that tends to push the rear end outwards round bends, and thus raises the safe cornering speed. The rear axle is set on the ideal trajectory, with a rear-wheel angle of less than 2° in most situations, for stability and efficacy. The Active Drive chassis with four-wheel steering enhances dynamic handling, with sound, reassuring response for outstanding driving pleasure.

Unparalleled active safety

The Active Drive chassis with four-wheel steering also improves safety for heightened reassurance during avoidance manoeuvres. In an emergency situation, the rear-wheel angle can rise to 3.5°. Cut-in of the ESC (Electronic Stability Control) system, specially configured for a sporty driving style, is delayed, so that the manoeuvre can be performed both safely and more swiftly. ESC only switches in when necessary, and is applied gradually because it is synchronized with the rear-wheel turn action. Via the ESC/ABS unit, the 4WS control unit also detects asymmetrical braking situations, adapting the rear-wheel turn angle automatically to keep the car stable with no driver action required. This helps the driver keep control during critical situations, and ensures uninterrupted peace of mind during everyday driving conditions.

Dynamic control logic

Developed jointly by Renault and Renault Sport Technologies, the Active Drive chassis with four- wheel steering implements electronic control of vehicle dynamics. A sensor on the steering column sends steering wheel angle information via the CAN network to the 4WD control unit, located behind the rear axle. The 4WD control unit also inputs vehicle speed from the ESP/ABS unit. And it tracks steering wheel angle information to detect sharp steering wheel movements symptomatic of a sports driving style or avoidance situation. All these parameters are analysed to determine the required rear-wheel turn angle, which is implemented by means of an electric actuator on the rear axle. Dynamic vehicle behaviour is precisely modelled to set the ideal vehicle trajectory at each instant, on the basis of the driver’s input and the actual situation of the vehicle. The controller and electric actuator are supplied by Aisin, a Japanese equipment supplier reputed for its experience in four-wheel steering systems.

High-performance engines

The diesel version of Renault Laguna GT is powered by a 2.0 dCi engine, best-in-class for performance, driveability and acoustics. In this implementation, it yields exceptional peak power of 180hp (131kW) at 3,750rpm. Peak torque of 400Nm is available from 2,000rpm, for prompt, consistent, sustained build-up through to 5,000 rpm. A reduced-inertia variable-nozzle turbocharger enhances dynamic response at low revs to achieve superlative performance: 29.6 seconds for the 1,000m standing start, and 0 to 100kph in 8.5 seconds. This new unit is fitted with a particulate filter and EGR valve with enhanced cooling, which makes intense driving pleasure perfectly consistent with environmental protection: mixed-cycle fuel consumption is just 6.5 litres/100km, which translates into CO2 emissions of just 172g/km. With its ultra-fast glow plugs, the 180hp 2.0 dCi unit roars into action instantly when the Start button is pressed, even in conditions of extreme cold (down to -23°C).

The petrol version of Renault Laguna GT is powered by a sports version (205hp/150kW at 5,000rpm and 300Nm from 3,000rpm) of the two-litre 16-valve unit, derived from Renault Sport technology as featured on M├ęgane Renault Sport, and specifically reworked for Renault Laguna GT, to yield the best in performance, handling and intense driving pleasure. It is superbly versatile, combining velvet smoothness with astonishingly crisp response, ideal for sports usage.

Design features such as the special air-intake system and twin-scroll turbo ensure the rev- counter leaps forward at the slightest touch of the throttle. Renault Laguna GT 2.0T accelerates from 0 to 100kph in 7.8 seconds and takes 28s to cover 1,000 metres from standstill. Yet fuel consumption is a very reasonable 8.2 litres/100km, which makes for CO2 emissions of just 194g/km.

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