Alfa 147 GTA In The UK | Part Four

Engine And Gearboxes

Power is provided by the same 40HC all-aluminium 3.2 litre V6 24-valve engine as that fitted to the Alfa 156 GTA and Sportwagon GTA. It is a spirited, widely acclaimed engine derived from the now classic three-litre V6 24-valve unit fitted to Alfa’s top-of-the-range 166 and GTV models.

However it differs from the 3.0 litre unit in many key respects. Power could simply have been increased by adjusting the timing, fuel system and electronics. But instead, Alfa Romeo’s engineers changed the crankshaft and pistons to increase cylinder capacity to 3.2 litres, and lengthened the stroke to 78 millimetres. This was done with one specific aim: to ensure absolute performance and high power and torque peaks, combined with smooth, linear power delivery from low speeds. For this reason, the 3.2 V6 24v unit delivers sensational performance, but it is also very docile. The GTA’s objective is to offer sensations unique to a racing car, yet still be very easy to drive and entirely suitable for everyday use.

The Alfa 147 GTA develops 250 bhp at 6200 rpm, with a maximum torque of 221 lb.ft at 4800 rpm. These figures are complemented by a torque curve that offers high numbers at low speeds. Thus, the car can cruise in sixth gear at less than 2000 rpm, and accelerate rapidly and smoothly away without the need for changing gear.

The increased cylinder capacity required further changes. For example, the control unit software has been rewritten, the cooling system has been upgraded with the addition of an engine oil radiator – and the intake and exhaust ports have been tuned by applying a new timing pattern.

The transmission has also been reinforced. The halfshafts are new, while the clutch is larger and the six-speed gearbox contains new, sturdier components. The current manual gearbox will be joined later in the year by a Selespeed version. Developed by Magneti Marelli, this sophisticated electro-hydraulic system has a Formula 1-derived operation that makes for swifter gear shifts at both low and high speeds.

The 3.2 litre V6 24-valve unit installed in the Alfa 147 GTA already meets the tough Euro 4 exhaust emission limits.

Safety

In addition to a braking system with outstanding performance (consisting of 305 mm ventilated front discs with four-piston Brembo callipers, and 276 mm rear discs), the Alfa 147 GTA also comes with state-of-the-art electronic systems for controlling the car’s dynamic performance: from braking to traction.

Thus ABS anti-lock braking is combined with EBD to distribute brakeforce over front and rear wheels, and a sophisticated VDC unit controls dynamic stability on corners, complemented by MSR and ASR (the former modulates braking torque when changing down through the gears, while the latter limits wheelspin during acceleration).

ABS with EBD

The new Alfa 147 GTA is fitted as standard with a Bosch 5.7 ABS anti-lock braking system, one of the most advanced units currently available. The system incorporates an electronic brakeforce distributor (EBD). The beauty of this system – which comes with four active sensors, four channels and a hydraulic control unit with 12 solenoids – lies in the fact that its active sensors can process a wheel input signal themselves, instead of passing it on to the control unit. The system can therefore activate itself more quickly and also detect speed signals close to zero (passive sensors do not detect speeds lower than 4 km/h). They are also less sensitive to interference caused by electromagnetic fields and road surface heating.

Because they can detect very low speeds, the active sensors also allow more effective use of the satellite navigation system to allow more accurate updating of data on the route covered by the car.

EBD distributes braking action over all four wheels to prevent them locking, and ensures full control of the car in all situations. The system also adapts its operation to the amount of grip available, and brake pad efficiency, so as to reduce pad overheating.

VDC - MSR

To ensure control of the car under all conditions, the Alfa 147 GTA is also fitted with VDC (Vehicle Dynamic Control) that made its first appearance on the Alfa 166 3.0 V6 24v.

This innovative system is permanently engaged and is activated under extreme conditions when vehicle stability is at risk, helping the driver to control the car. As befits a true Alfa, the VDC is a sporting system that does not interfere prematurely, and allows the driver to enjoy the full satisfaction of controlling the car as long as conditions do not become critical.

To achieve this result, VDC continually monitors tyre grip in both longitudinal and lateral directions. If the car starts to slide, VDC cuts-in to restore directionality and stability. It uses sensors to detect rotation of the car body about its vertical axis (yaw), lateral acceleration, and the steering wheel angle set by the driver (which indicates the chosen direction). It then compares this 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 lose adhesion (understeer or oversteer).

To restore the required trajectory, it then generates a yawing movement in the opposite direction to the movement that gave rise to the instability, by braking the appropriate wheel individually, and reducing engine power (via the throttle). The key attribute of the system, designed by Alfa Romeo engineers, is that 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). Engine power reduction is also contained to ensure the maintenance of outstanding performance and great driving satisfaction at all times.

As it carries out its complex task, VDC stays in constant communication with the brake sensors and engine control unit, but also with:

  • The steering wheel and steering column (via the steering sensor)
  • The control panel (active warning lights)
  • The body computer that constantly exchanges information with the ABS, engine management unit and automatic transmission unit
  • The electronic throttle (that communicates with the ABS in turn)
  • A gyroscopic sensor installed on the passenger compartment floor to record vehicle yaw angle and lateral acceleration

ASR

The Alfa 147 GTA also comes with ASR (Anti Slip Regulation), a feature of the VDC system, to limit wheelspin in cases of low road surface grip. This sophisticated system works at any speed and prevents the driven wheels from spinning by adjusting torque according to the grip coefficient detected at the time of slip.

The system 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 driven wheels to spin (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 spins (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.

The ASR optimises vehicle safety and is particularly useful when grip is lost, (icy multi-storey car park ramps are one example), and whenever the asphalt does not guarantee a constant coefficient of friction.

Another advantage of ASR is the lower stress exerted on mechanical parts such as the differential and gearbox, due to more effective control of low speed take-off and traction.

ASR is activated automatically whenever the engine is started. To turn off the system, all the driver has to do is press a switch on the central console. When ASR is operating, a warning light on the control panel flashes. A control panel warning light also illuminates to indicate system faults or irregularities.

ASR deactivation is required when snow chains are used because the wheels must be able to slip by small amounts to pile up the snow so that force can be transmitted to the ground.

Published 30 October 2002 Melanie Carter
 

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