FACTfile - Alfa Romeo 147 GTA - Page 2

Power has been increased by making radical mechanical changes

Engines and Gearboxes
The Alfa 147 GTA power unit is the same 3.2 V6 24 valve engine fitted to the Alfa 156 and Alfa Sportwagon GTA. It is derived from the 3 litre V6 24 valve unit fitted to the Alfa 166 and GTV models. The 147 GTA engine differs from its predecessor in certain respects. First and foremost, power has been increased by making radical mechanical changes. The power could simply have been increased by adjusting the timing, fuel system and electronics.

But instead the engineers changed the crankshaft and pistons on the GTA to increase the cylinder capacity to 3.2litres and lengthened the stroke to 78 millimetres. This was done to ensure absolute performance and high power and torque peaks combined with smooth, gradual delivery from low speeds. For this reason, the 3.2 V6 24v unit can deliver a top speed of 246 km/h and 0 to 100 km/h in 6.3 seconds - but can also be used as an everyday car. The aim of the GTA is to offer a racing car feel yet still be perfectly serviceable for everyday use.

The 3.2 V6 24v unit fitted to the Alfa 147 GTA develops 250 bhp at 6200 rpm with a maximum torque of 300 kgm (30.6 kgm) at 4800 rpm. These figures are complemented by a torque curve that permits high values at low speeds. The car can also travel in sixth gear at less than 2000 rpm and unleash speed spurts without changing gear. The increased cylinder capacity naturally 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 half-axles are new, while the clutch is bigger and the six-speed gearbox offers new, sturdier components. The current manual gearbox will be joined in 2003 by a Selespeed version. Developed by Magneti Marelli, this sophisticated device has a Formula 1-derived operating system that makes for swifter gearshifts at both low and high speeds. The 3.2 V6 24 valve unit fitted on the Alfa 147 GTA already meets the tough Euro 4 emission limits.

Safety
In addition to a braking system with outstanding performance (consisting of305 mm ventilated front discs with dual pump Brembo callipers and 276 mm rear discs), the Alfa 147 GTA also comes with state-of-the-art electronic devices for controlling the car's dynamic performance: from braking to traction. Hence not merely an ABS but also an EBD to distribute brake force over front and rear wheels and a sophisticated VDC to control dynamic stability on corners, complemented by MSR and ASR (the former moderates brake torque while changing down through the gears while the latter limits wheel slip during acceleration).

ABS with EBD
The new model is fitted as standard with a Bosch 5.7 ABS, one of the most advanced units currently available on the market with an integral electronic brake force distributor (EBD). This device - which comes with four active sensors, four channels and a hydraulic control unit with 12 solenoids - has active sensors that can process a wheel input signal themselves instead of sending it on to the control unit. It can therefore cut in 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. An electronic brake force distributor (EBD) distributes braking action over all four wheels to prevent them locking and ensure full control of the car in all situations. The system also adapts its operation to wheel grip conditions and brake pad efficiency to reduce pad overheating. This ABS is so sophisticated it ensures: maximum braking force on each wheel close to locking depending on grip on the ground; full car control even with the brake pedal pressed to the floor; high ability to adapt automatically to different service conditions and very prompt responses.

VDC - MSR
The 147 GTA is also fitted with a VDC (Vehicle Dynamic Control) device that first made its appearance on the Alfa 166 3.0 V6 24V. The VDC cuts in under extreme conditions when car stability is at risk and helps the driver control the car. The VDC - which is permanently engaged - is not activated under normal driving conditions but does cut in when the situation is just about to become critical.

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 then generates a yawing movement in the opposite direction to the movement that gave rise to the instability by braking the appropriate wheel (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). However engine power reduction is contained to ensure performance and driving satisfaction.

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