Car Design News: New Fiat 500 In Depth

Page 1: Manifesto
Page 2: In brief
Page 3: Joint effort
Page 4: Engines
Page 5: Gearbox
Page 6: Safety
Page 7: Experiencing the 500
Page 8: Standard features
Page 9: Specifications

Class-beating safety

The Fiat 500 does not only offer styling with plenty of personality, modern, reliable engineering, lavish equipment and outstanding comfort. It is also an extremely safe car. More than individual devices it is a combination of various systems that make it one of the safest cars in its segment.

The new model is the first car in this category to offer up to 7 airbags (front, side, curtain- and knee-bags are all standard throughout the range, except for the Naked version). And the new 500 also proposes a number of sophisticated technical solutions to control the car�s dynamic behaviour. They include ABS complete with EBD, the sophisticated ESP (Electronic Stability Program), ASR (Anti Slip Regulation), HBA (Hydraulic Brake Assistance) and a Hill Holder device. And to guarantee the safety of the occupants, the bodyshell of the new model is designed to respect all the latest impact resistance criteria (it is the first super-mini with a front structure designed specifically to improve compatibility between vehicles in a head-on impact), and is rigid around the passenger compartment to protect occupants with high-absorption areas on the outside.

Seat-belts with double pretensioners and load limiters are standard on the front seats, with three-point belts at the rear. The front and rear seats are fitted with antisubmarining devices that prevent the occupant from sliding forward, under the seat-belt. Isofix attachments for child seats are standard throughout the range.

The Fiat 500 is fitted with all the dynamic and comfort features that ensure occupants can tackle any type of road comfortably and safely. The credit also goes to the suspension: an independent MacPherson system at the front, and semi-independent interconnected wheels with a torsion axle at the rear. The two layouts have evolved from a Magneti Marelli design and have been used on other Fiat models in the past; they have now been revised and modified for the new car, to guarantee outstanding handling and the highest possible level of comfort.

Active safety

The braking system on the new car has two independent cross-over circuits to guarantee prompt, smooth braking and shorter stopping distances. The pedal has a short stroke, so that the characteristics of the servo assist are exploited in full.

The front discs have a diameter of 240 mm; they are solid for versions with the 1.2 8v engine and ventilated for the 1.3 Multijet, with a diameter of 257 mm for versions with the 100 bhp 1.4 16v. The rear brakes mount drums (180 mm) on the 1.2 8v and 1.3 Multijet, and discs (240 mm) on the 1.4 16v. The 9� brake servo makes braking easier and more effective, decreasing the effort needed on the pedal.

ABS system

The ABS on the Fiat 500 has four active sensors, four channels, a hydraulic control unit with eight solenoids and comes complete with EBD (Electronic Brake Distribution). The system can guarantee the best possible braking effort even with each wheel close to locking, which means it is possible to control the direction of the car fully in emergency situations using the steering wheel.

The strong points of the system are the active sensors, which process the wheel speed data themselves (without having to send them to the control unit); they can read values very close to nought (passive sensors do not register speeds below 2.5 km/h) and are less sensitive to disturbance caused by electromagnetic fields.

This advanced ABS system is supplemented by electronic brake force distribution, EBD, which distributes the braking force between the front and rear wheels to prevent the rear wheels from locking, guaranteeing a balanced response from the car in all conditions. The system also adapts to the grip conditions of the wheels and the efficiency of the brake pads, and it reduces the temperature of the front brakes and the effort demanded from the brake servo.

ESP (Electronic Stability Program)

The new Fiat 500 offers the sophisticated Electronic Stability Program to guarantee complete control over the car; this program cuts in when conditions are close to the limit, and the car�s stability is at risk, to help the driver to control the vehicle (the device is standard with the 1.4 engine and an option with the other two).

To do so, ESP constantly verifies how the tyres grip the ground, longitudinally and laterally, and if the car does skid, it cuts in to recover the trajectory and trim stability. It incorporates sensors that measure the wheel speed, the vehicle�s rotation around its vertical axis (yaw speed), the lateral acceleration and the steering angle set by the driver (which indicates his chosen direction). It then compares these data with the parameters processed by a computer and uses a complex mathematical model to establish whether the car is taking a bend within the grip limits, or whether the front or rear is about to veer (understeer or oversteer).

To bring it back to the correct trajectory, the system generates a yaw moment opposite to the one that caused the instability, singly braking the appropriate wheel (nearside or offside), and reducing the engine power by adjusting the throttle valve. This is where the device developed for the Fiat 500 differs from other systems. Its intervention on the brakes is modulated to be as gentle as possible (therefore without disturbing the driving), and the reduction in engine power is limited, to guarantee excellent performance and enjoyable driving at all times. ESP is always engaged.

ASR (Anti Slip Regulation) and MSR (Motor Schleppmoment Regelung)

To limit any slipping of the driving wheels when grip on the road is poor, the new Fiat 500 is equipped with a sophisticated device that controls traction automatically. It is known as ASR (Anti Slip Regulation), and is standard equipment on all versions that mount the ESP system. ASR functions at all speeds and adjusts torque on the basis of the grip detected.

Based on the number of wheel revs calculated by the ABS sensors, the device calculates the degree of slipping and activates two different control systems to recover grip:

� when an excessive demand for power causes both drive wheels to slip (for example when aquaplaning or accelerating on an uneven, snow-covered or icy road surface), the system reduces engine torque by decreasing the throttle valve aperture and thus the air flow;

� if only one wheel slips (for example the wheel inside a bend following acceleration or dynamic changes to the load), this is automatically braked without the driver having to press the brake pedal. The effect obtained is similar to that of a self-locking differential.

ASR helps to maintain vehicle stability, and it is particularly useful when there is a loss of grip (just think of the ramps in a garage in Winter) and when the paving does not guarantee homogeneous friction.

Another advantage of ASR that should not be overlooked is the reduction of stress on mechanical organs such as the differential and gearbox, which is achieved by controlling take-off and traction at low speeds.

ASR is engaged automatically every time the engine is started, but can be excluded by a switch on the centre console. When ASR is activated a telltale on the instrument panel flashes. If the telltake in the control panel comes on, but the LED on the switch is off, this indicates a malfunction or irregularity in the system. ASR must be de-activated when snow chains are mounted, because in order to transmit torque to the ground, the wheel has to be able to �pile up� snow with small slips that the ASR system tends to avoid.

If the driver changes down suddenly and grip is poor, the MSR device (Motor Schleppmoment Regelung) takes over, returning torque to the engine and preventing slipping due to wheel lock.

HBA (Hydraulic Brake Assistance)

The Fiat 500 adopts a device that assists in emergency braking. On cars fitted with ESP this function is performed electronically by the ABS control unit and it is called HBA (Hydraulic Brake Assistance).

During �panic� braking, most drivers recognise an emergency situation and put their feet down very rapidly on the brake pedal, but not with the necessary additional effort. Because, unless he is a professional driver, the motorist is accustomed to braking by applying a certain �load� to the pedal, and like all automatic gestures repeated over and over again, he tends to use the same effort in all circumstances.

On the new model, at this point the Brake Assist devices are triggered, and although the pressure on the pedal remains the same, they ensure the same deceleration that you would achieve by braking with every possible force.

The panic braking assist is also useful for more expert drivers who do brake rapidly, and with the right amount of energy when necessary. Because in any case the system reduces braking implementation time, i.e. the time between the moment he applies the force on the pedal and the moment that the circuit reaches maximum pressure and can give its best performance.

Hill Holder

The Hill Holder is a system that helps the driver on hill starts. It cuts in when the ESP control unit perceives a difference in the inclination of the car through a longitudinal acceleration sensor on the floor under the front passenger seat. During a hill start, the control unit prepares to intervene when first speed is engaged and the brake and clutch pedals are depressed. The pressure on the front brake callipers is maintained for about 2 seconds after the driver releases the brake pedal, allowing him to set off without difficulty. The Hill Holder is not activated when the car is started downhill with first speed engaged. Similarly, when reverse is engaged, the system is activated for downhill starts, and it is not activated for uphill starts.

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