2004 Alfa Romeo 156 Crosswagon

Four wheel drive

The Alfa Romeo 156 Crosswagon transmission features 4 permanently engaged drive wheels, three differentials and torque distribution preferentially to the rear.
The Torsen C differential continuously modulates torque distribution between front and rear axles according to grip. This feature makes for a sporty drive that in turn increases active safety.

The mechanical modulation is continuous and progressive. It conveys an optimum driving sensation that is satisfying and easy for the driver. Torque distribution takes place without any time lag. The car’s grip performance adapts gradually in linear fashion to changing road conditions. This mechanical system is complemented by an electronic system for extra performance and safety margins in line with the Alfa Romeo philosophy.

The Alfa Romeo 156 Crosswagon is absolutely cutting edge as far as engineering is concerned and offers unexpected benefits.
Beginning with ride comfort. The increased ground clearance and generous tyre size brings a decided improvement when driving over obstacles while the stiffer body helps lower sound resonance effects.

Because not all the torque needs be transmitted through the front axle, it has been possible to configure the geometry of the double wishbone front suspension for ride comfort. Permanent traction makes it possible to increase roadholding, driving satisfaction and smoothness of response. No other four wheel drive, implemented using electronic couplings, can offer the same optimum balance between oversteer, understeer and smoothness of response typical of the Alfa Romeo 156 Crosswagon, that translates into great roadholding and active safety. Preferential torque distribution to the rear axle adds further driving satisfaction because vehicle handling is improved while guaranteeing maximum stability during sudden high speed lane changes on the motorway, as sometimes happens during emergency manoeuvres.

3. Off-road performance is also better than expected. The driver need no longer fear transmission lag and the combination of electronic and mechanical control makes differential locking effective in extreme conditions. For example, the car negotiates demanding obstacles like twists, where one wheel is completely off the ground, with complete aplomb. In short, the Alfa Romeo 156 Crosswagon is four wheel drive Alfa Romeo style: an essentially mechanical system complemented by the most advanced electronics to assure maximum driving comfort together with optimum performance and total safety.

Suspension

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

The earlier version 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 pull-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 Alfa Romeo 156 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

Power and character. The Alfa Romeo 156 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 with the powerful 1.9 JTD 16v Multijet developing 110 kW (150 bhp) 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 (31 kgm) 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 Romeo 156 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 Romeo 156 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 Alfa Romeo 156 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:

• a Body computer that constantly exchanges information with the ABS, engine management unit and automatic transmission unit;
• an electronic throttle (that communicates with the ABS in turn);
• a control panel (active warning lights);
• the steering wheel and steering column (via the steering sensor);
• 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 Romeo 156 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.

Short history of Alfa Romeo 4×4 cars

The first four wheel drive system in Alfa Romeo’s history made its debut in 1951 on the AR51 – 1900, an off-road car with state-of-the-art engineering features designed for military use. The ‘Matta’ (or crazy car – as it was affectionately dubbed by those who appreciated its exceptional off-road properties) is now a real cult item appreciated far beyond the restricted circle of Alfa Romeo collectors.

The Alfa Romeo 33 4×4 made its debut in 1983. The layout adopted for this compact saloon meant that the rear wheel drive had to be engaged by means of a lever in the passenger compartment. A central differential prevented any slippage between both axles. Because it offered higher ground clearance than front wheel drive cars, the 33 4×4 acquitted itself well in many critical situations and could pass easily from snowy surfaces to unsurfaced roads. Altogether a multi-facetted car that allowed great flexibility of use. In 1991, the Alfa 33 (again) was fitted with a sportier interpretation of the four wheel drive concept. The transmission layout of the new Permanent 4 (this was the name of the version) was more complex than its predecessor: a set of sensors managed the action of a viscous coupling that transferred movement to the rear wheels (generally free) when it detected significant differences between wheel rotating speeds across both axles. These features assured the 33 outstanding dynamic performance, an up-to-date blend of high performance, sports handling and top level active safety.

The following year saw the arrival of the Alfa Romeo 155. The new Quadrifoglio 4 tag was the emblem of state-of-the art Alfa Romeo sportiness. One specific feature of the Alfa Romeo 155 Q4 was the presence of a permanent four wheel drive system with three differentials: a conventional unit at the front; a central epicyclic unit that engaged directly with the gearbox layshaft incorporating an integral Ferguson viscous coupling – and a Torsen unit at the rear. Under normal conditions, the central distribution distributed drive torque with a slight preference to the rear wheels. If one of the two axles lost grip excessively compared to the other, the Ferguson coupling cut in to transfer drive torque (up to 100%) gradually to the wheels with more grip. The efficacy of the system was further increased by a Torsen rear differential that acted as a self-locking unit and allowed the wheels to turn at different speeds.

This transmission configuration was combined with a particularly advanced ABS. This technical configuration ensured that the 155 Q4 remained glued to the ground and was easy and entertaining to drive while remaining safe in every situation. These attributes were also displayed by the racetrack versions that fought out the German touring car speed championship. In 1993, the Alfa Romeo 155 V6 TI saw off the competition to triumph in the DTM with Larini at the wheel.

Alfa Romeo brought the incredible technical experience it had built up over the years to bear when it produced a four wheel drive version of its range leader, the 164. In December 1993, customers were able to buy a Alfa Romeo 164 Q4 powered by the legendary 231 bhp V6 engine. In this case, the four wheel drive layout had been further developed to ensure maximum performance and peak driving comfort. The heart of the system was the central Viscomatic viscous coupling developed exclusively by Alfa Romeo in conjunction with Steyr-Puch. The Viscomatic was managed by an on-board electronic system that communicated in real time with the engine control unit and ABS control unit. Moment by moment, the system detected and processed information on four different parameters: total drive torque requested, speed, steering angle and slip difference between front and rear axles. It was able to adjust drive torque distribution between the axles with incredible speed on the basis of vehicle speed, cornering radius, engine rpm, throttle opening and closure and ABS parameters. This guaranteed improved torque distribution at any moment and in any situation. In this case too, the Q4 drive system was based on a Torsen self-locking rear differential. This rear differential was responsible for the important task of redistributing the torque allocated to the rear end (in real time) between the wheels on the rear axle: this benefited traction and also car handling over mixed routes. An epicyclic unit was also fitted between the coupling and rear differential to amplify speed differences between coupling input and output. This made it faster and more sensitive while reducing the level of torque managed by the coupling.

The latest addition to the Q4 heritage is the Alfa Romeo 156 Crosswagon Q4.

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