FACTfile - Alfa 156 Crosswagon – Page 2

Suspension
Driving satisfaction is always a strength of Alfa Romeo cars and the Crosswagon is no exception. The model therefore repeats the layout adopted on the 156 with some adjustment: high double-wishbone at the front, MacPherson at the back with transverse rods of different lengths.

The suspension has been redesigned and optimised due to the car's higher ground clearance compared to the basic model while also maintaining the steering feel and precision typical of an on-road Alfa 156. The rear suspension has also been revised to increase car stability during turn-in, release and breaking to adapt to four wheel drive performance.

In detail, the choice of a double wishbone layout for the front suspension meets a specific aim: to achieve maximum lateral hold, a highly effective and precise steering response and excellent traction - and to wed these specifications with an ability to absorb and damp road surface roughness typical of the most comfortable cars in the segment. The double wishbone layout allows high longitudinal flexibility to be achieved on the wheel side without impairing roadholding on corners and steering dynamics. The car's on-road behaviour is aided by a rear suspension that gives the model the greatest stability during high speed manoeuvres and all the agility required of a true sports car over tight mixed routes. Hence the choice of a MacPherson suspension featuring asymmetrical arms and refined elastokinetic properties.

On the Crosswagon, the rear suspension is connected to the chassis by a crossmember made out of vacuum cast aluminium. The benefits of the MacPherson strut layout include low weight, great comfort (assured by extensive wheel travels and longitudinal flexibility) and numerous ride control options. The front and rear suspension layout also allows the various joints, including the steering arm joints, to yield in a calibrated manner without this affecting driving precision. The set of features adopted allowed us to achieve the very highest level results in terms of insulating out all noise and absorbing the minor roughness that often causes annoying knocking sounds to reverberate from the body.

Engine and Gearbox
The Crosswagon combines the great driving comfort offered by its suspension with all the exuberant character of an Alfa sports model. This explains why the new model is equipped initially with the powerful 1.9 JTD 16v Multijet developing 110 kW plus a 6 speed manual gearbox with sports ratios. The unit is a 4 cylinder in line engine with a bore of 82 millimetres and a stroke of 90.4 mm, capable of delivering a power output of 110 kW at 4000 rpm and a torque of 305 Nm at 2000 rpm. The new turbodiesel has undergone several engineering changes to increase performance and engine torque at low speeds and to reduce noise and vibration levels.

For example, the Common Rail system used on the 1.9 JTD 16v Multijet includes two new strategies for automatically calibrating and balancing the diesel injected to lower noise and reduce vibration.

Braking System and Active Safety Systems
The Alfa Crosswagon braking system is hydraulic, power-assisted and consists of two independent crossover circuits. This particularly effective system offers prompt, smooth braking and short stopping distances. In particular, the front discs, derived from the GTA, are ventilated with a diameter of 330 millimetres and come with four piston (38 and 42 mm) aluminium fixed Brembo callipers. The rear discs are only slightly smaller at 276 millimetres.

In addition to a high-performing brake system, the Alfa Crosswagon also comes as standard with a BOSCH 5.7 ABS, one of the most advanced systems available on the market today. It features four active sensors and a 12 valve control unit. The ABS contains an electronic brakeforce distributor (EBD). This device apportions braking action over all four wheels to prevent locking and ensure full control of the car under all conditions. The system also adapts its operation to wheel grip conditions and brake pad efficiency to reduce pad overheating.

The Crosswagon also assures absolute mastery of the car in all conditions, however extreme, due to its VDC (Vehicle Dynamic Control) and ASR (Anti Slip Regulation) systems. More specifically, the VDC is Alfa Romeo's version of the ESP (Electronic Stability Program), an innovative device that cuts in under extreme conditions when car stability is at risk and also helps the driver control the car. As befits a true Alfa, the VDC is a sporting device that allows outstanding roadholding. It allows the driver the full satisfaction of controlling the car as long as conditions are normal but cuts in just before things become critical. The VDC is permanently engaged. The MSR (Motor Schleppmoment Regelung) cuts in when the gear is shifted down abruptly in low grip conditions. This device restores torque to the engine to prevent the wheel skidding as a result of lock.

To achieve this result, the VDC continually monitors tyre grip in both longitudinal and lateral directions. If the car skids, it cuts in to restore directionality and ride stability. It uses sensors to detect rotation of the car body about its vertical axis (yaw speed), car lateral acceleration and the steering wheel angle set by the driver (which indicates the chosen direction). It then goes on to compare these data with parameters generated by a computer and establishes - via a complex mathematical model - whether the car is cornering within its grip limits or if the front or rear is about to skid (understeer or oversteer). To restore the correct trajectory, it generates a yawing moment in the opposite direction to that which gave rise to the instability by braking the appropriate wheels (interior or exterior) individually and reducing engine power (via the throttle). This is the key attribute of the device designed by Alfa Romeo engineers. It acts in a modulated fashion on the brakes to ensure the action is as smooth as possible (and the drive is not therefore disturbed). The engine power reduction is contained to ensure outstanding performance and great driving satisfaction at all times.

As it carries out its complex task, the VDC stays in constant communication with the brake sensors and engine control unit but also with:
1. The body computer that constantly exchanges information with the ABS, engine management unit and automatic transmission unit;
2. An electronic throttle (that communicates with the ABS in turn);
3. A control panel (active warning lights);
4. The steering wheel and steering column (via the steering sensor);
5. A gyroscopic sensor installed on the passenger compartment floor to record car yaw and lateral acceleration.

An integral part of the VDC is the ASR (Anti Slip Regulation) system which optimises traction at any speed with the aid of brakes and engine control. The device computes degree of slip on the basis of wheel rpm calculated by the ABS sensors and activates two different control systems to restore grip: when an excessive power demand causes both drive wheels to slip (e.g. in the case of aquaplaning or when accelerating over an unsurfaced, snowy or icy road), it reduces engine torque by reducing the throttle opening angle and thus air flow; if only one wheel slips (e.g. the inside wheel following acceleration or dynamic load changes), this is automatically braked without the driver touching the brake pedal. The resulting effect is similar to that of a self-locking differential. This enables the Alfa Crosswagon to readily negotiate icy roads - only one wheel requires grip to transmit drive to the car - as well as off-road twists, when an obstacle leaves the vehicle with only two wheels operative and, of the other two, one is off the ground. The ASR is activated automatically whenever the engine is started but must be turned off by means of a cut-out switch on the central console. Finally, ASR deactivation is required when snow chains are used because the wheel must be able to slip by tiny amounts to pile up the snow so that force can be transmitted to the ground and the ASR tends to prevent this occurring.

© italiancar.com.au 29/02/04

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