new models: Alfa Romeo 147 GTA
In addition to a braking system with outstanding performance ( consisting of 305 mm ventilated front discs with dual pump Brembo calipers 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 brakeforce 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 ).
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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 brakeforce distributor ( EBD ). The advantage of this device - 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 sending it on to the control unit. The system 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.
This cutting-edge ABS is complemented by an electronic brakeforce distributor ( EBD ), that 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
To ensure absolute mastery of the car under al conditions, however extreme, the Alfa 147 GTA is also fitted with the VDC (Vehicle Dynamic Control) device that first made its appearance on the Alfa range leader: the Alfa 166 3.0 V6 24V.
This innovative device 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 to enjoy the full satisfaction of controlling the car as long as conditions remain normal and does not cut in until the situation is just about to 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 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 ). 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:
- the steering wheel and
steering column ( via the steering sensor );
The Alfa 147 GTA also comes with ASR ( Anti Slip Regulation ), a feature of the VDC system, to limit drive wheel slip in cases of low road surface grip. This sophisticated device works at any speed and prevents the drive wheels from slipping by adjusting torque according to the grip coefficient detected at the time of slip.
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;
The ASR maintains vehicle safety as much as possible and is particularly useful when grip is lost ( icy multi-storey car park ramps are one example ) and whenever the asphalt does not guarantee even friction.
Another not inconsiderable advantage of the 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.
The ASR comes on automatically whenever the engine is started. To turn off the device, all you have to do is press a switch on the central console. When the ASR is active, a warning light on the control panel flashes. A control panel warning light comes on ( with the switch led off ), to indicate system faults or irregularities.
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 avoid this type of action.
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