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Wednesday, January 27, 2016

How The Fiat 500 Handles Snow

Fiat 500C in Snow

The Fiat 500 may be small, but it packs a lot of capability within its lean frame. Take for instance driving in snow. Fiat has given the 500 a sophisticated traction control system. Throw a set of snow tires on when you're in the really deep stuff and you have a surprisingly good snow car. As Italy is a mountainous country, it should be no wonder! Watch these videos and you'll be a believer.

This Fiat 500 tackles a steep icy driveway with 7 inches of fresh snow.

Here is a look at the technology that helps the Fiat 500 tackle slippery conditions and maintain its composure.

The Fiat 500 combines its Antilock Brake System (ABS) with Electronic Stability Control (ESC) and All-Speed Traction Control (TCS) to help the driver maintain control. ABS prevents wheel lockup during braking, helping retain directional stability and steering control.

The anti-lock brake system consists of the following components:

  • Integrated Control Unit (ICU)
  • Hydraulic Control Unit (HCU)
  • Antilock Brake Module (ABM)
  • Four Wheel Speed Sensors (WSS) - Four sensors (one at each wheel)
  • Steering Angle Sensor - integrated into Steering Column Module.
  • Dynamics Sensor Module - includes Yaw rate and lateral acceleration sensors

Good demonstration of the Fiat 500's Electronic Stability Control System.

The ABS operates at vehicle speeds above 5–8 km/h (3–5 mph). During braking, if wheel locking is detected by Wheel Speed Sensors (WSS), the hydraulic pressure in the four wheel circuits is modulated to prevent wheel skidding. Each wheel circuit has their own electric solenoids to maximize braking, but to ensure vehicle stability, both rear wheel solenoids receive the same brake pressure as the wheel with the highest slip. The system switches off when the car slows to a speed of 5–6 km/h (3–4 mph), which may allow the wheel to lock up, and is normal and can help when on snow or gravel.

An interesting fact it that although the ABS prevents complete wheel lockup, some wheel slip is desired in order to achieve the best braking performance. Wheel slip is allowed to reach up to 25–30 percent, and may result in the typical tire chirping noise heard during ABS operation. This should not be thought of as wheel lock up, and can be seen on the road surface as light patch markings and not the dark black markings made by a skidding tire.

Fiat 500C Winter Drive

The Fiat 500's Electronic Stability Control (ESC) helps maintain directional stability under all condition, including snow, ice or gravel. If there is a discernible difference between driver input through the steering wheel and the Fiat 500’s path, ESC applies selective braking and throttle input to guide the vehicle back on to the driver’s intended path within the limits of available traction.

Electronic Stability Control (ESC) includes Hydraulic Brake Assist, Traction Control, Electronic Roll Mitigation, and Brake Lock Differentials.

ESC uses the ABS along with the following components to operate:

  • Dynamics (ESC) Sensor - under the center console, near the center of gravity of the car for efficient sensing.
  • Steering Angle Sensor (SAS) - located in the steering column.

Electronic Stability Control (ESC) has two modes in Fiat 500 models. Abarth models have an additional OFF mode.

Full On
This is the normal operating mode for ESC and is on when the vehicle is started. This mode is used for most driving situations and should only be turned to Partial Off for the reasons listed below.

Partial Off
This mode is intended to be used if the vehicle is in deep snow, sand or gravel conditions and more wheel spin than ESC would normally allow is required to gain traction. In Partial Off mode, Traction Control is deactivated, and ESC doesn't intervene as quickly as in the Full-On mode.

Fiat 500C Skiing

Traction Control System (TCS) prevents wheel slip when accelerating on slippery surfaces and works up to 85 mph (137 km/h). The system uses signals from the ABS wheel speed sensors to determine when to apply the brakes to one or more wheels and when to reduce engine torque output to prevent wheel slip during acceleration. Because TCS can precisely control engine torque as well as applying the brakes, it is possible to achieve a smooth torque application to the wheels which greatly enhances traction.

The system is identified as “all-speed” traction control because by reducing engine power, braking effectiveness is maintained and the system can operate throughout the normal vehicle speed range.

The traction control system may be turned off or on by depressing the ESC Off switch button.

European Fiat 500C

The Brake Lock Differential System (BLDS) is part of TCS and offers similar performance as a locking differential. If one wheel starts slipping, the ABS slows the spinning wheel. This automatically transfers more drive torque to the wheel with traction. The advantages of BLDS over a mechanical locking differential are faster and more progressively intervention and lighter weight.

Hydraulic Brake Assist helps the driver overcome the tendency not to apply the brakes hard enough or quick enough to achieve the minimum stopping distance during a panic stop. In an emergency brake situation, the system applies maximum braking power, minimizing the stopping distance.

Electronic roll mitigation (ERM) anticipates if vehicle at risk of entering a potential roll situation and applies brakes individually and modulates throttle position as needed to keep the car stable.

Images: FCA NV
Information courtesy of FCA US LLC
Video: Camper1234599 YouTube Channel , Bergstrom FIAT YouTube Channel