Alfa 147 GTA In The UK | Part Three

Alfa Romeo 147 GTA

Alfa Romeo 147

MECHANICALS

Suspension

Alfa 147 GTA suspension is based on the combination of high double wishbones at the front, (the only car in its class to offer this configuration), and an advanced MacPherson arrangement at the rear. This engineering option has already brought the Alfa 147 great success and has been specially adapted to the upgraded features of the new car to ensure the Alfa 147 GTA of outstanding dynamic performance.

The suspension is the final outcome of a long and thorough development process carried out on the basic layout, with the aim of achieving the highest levels of driveability and handling. These features allow the driver complete control of the new car’s performance for the best possible results on the road. From the customer’s viewpoint, the new version:

  • Is responsive
  • Is smooth and accurate in its steering
  • Is very stable and easy to control, even when close to the limit
  • Features well contained body movements
  • Offers remarkable comfort in all service and road surface conditions

Front

The Alfa 147 GTA offers its drivers optimum control typical of front-wheel drive cars, plus outstanding responses and driving precision. This is particularly evident over varied routes. The credit for this goes first and foremost to the high double wishbone front suspension which was developed specifically for the model by the Fiat Research Centre and Alfa Romeo Research. It departs from the configuration used on the Alfa 147 in offering a reinforced lower beam, lower ride height, new spring and damper settings, a special strut that is fastened to the steering link in a different position – and a larger diameter anti-roll bar.

These engineering improvements increase the dynamic performance of the set-up, the structure of which consists of a cast iron lower arm, a steel strut and an upper light alloy arm. The coaxial spring-damper unit is connected to the body via a flexible mount and to the lower arm via a light alloy fork. For reasons of space and structural stiffness, the upper arm is jointed to an aluminium shell (anchored to the body) which acts as a support to the upper spring-damper attachment.

From a dynamic viewpoint, the high double wishbone layout combines long wheel travel with outstanding control. This is achieved because the upper arm is located higher than the wheel centre, which means that the area between wheel and power unit ancillaries can be exploited to the full.

Other benefits of this configuration include maximised tyre grip, improved traction even under extreme conditions, a self-alignment effect proportional to the lateral acceleration applied in a corner, superior steering precision and sensitivity, graduated steering wheel effort up to the grip limit, and the minimisation of pitching under extreme acceleration or braking.

Fluid dynamic bushes are used to hinge the upper suspension triangle to the bodyshell; Teflon split gaskets and bushes are loaded with glassfibre for the damper stems, and there are Teflon seals for the damper pistons.

Rear

The rear suspension has also undergone many technical improvements. The geometry and the constructional details of the tried and tested MacPherson configuration have both been revised. The outcome is a different body attachment position; revised spring settings; different damper and bush stiffness; and an anti-roll bar with a larger diameter.

The GTA’s MacPherson suspension also adopts innovative construction features. For example, the coil springs not only offer a different stiffness and lower ride height to those of the Alfa 147, but also rest on upper and lower plates with an interposed rubber ring to reduce noise levels. The anti-roll bar (connected directly to the damper via plastic connecting rods and jointed on steel ball joints) features a Cellasto upper end travel block (closed cell polyurethane that maintains its flexible properties over time). The new double-acting hydraulic dampers are pressurised and built in high strength steel with reduced thickness. Lastly, all the suspension arms and rear beam bushes are made especially for the Alfa 147 GTA.

The upper damper attachment displays a new tapered block fastening system. Assembly is easier and the system is more reliable because the attachment need not be bolted to the body.

These significant technical innovations and features improve performance and driving enjoyment still further. Suffice to say that the modified rear suspension can absorb obstacles more easily because the wheels ‘withdraw’ longitudinally to keep the car on its trajectory. The system also assures maximum directional stability when the car meets obstacles such as tram lines, or expansion joints on motorway bridges.

The rear suspension also increases the smoothness and alacrity of steering response, and means the car is more able to align itself automatically, even under extreme conditions. This is achieved by ensuring the wheels steer consistently under lateral load. The Alfa 147 GTA gains negative camber during roll due to the new rear suspension. In other words, cornering grip is increased by ensuring the roll centre position is more accurate, so as to improve the car’s general balance.

continues... | Part Four
Published 30 October 2002 Melanie Carter
 

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