Focus RS Clutch System Explained

The Heart of Performance: Understanding the Ford Focus RS Clutch

The Ford Focus RS, a name synonymous with performance and driving exhilaration, has captivated enthusiasts worldwide since its inception. Building on a legacy of groundbreaking models, the 2017 Ford Focus RS brought an unparalleled level of performance to the hot hatch segment, particularly in markets like the United States where it was eagerly awaited. A key component of this performance prowess lies within its sophisticated clutch system, intricately linked to its advanced all-wheel-drive (AWD) and dynamic driving modes. This article delves deep into how the clutch system operates on the Ford Focus RS, explaining its role in delivering the car's exceptional handling and exhilarating driving experience.

A Legacy of Performance: The RS Evolution

Since 1969, the RS (Rally Sport) badge has signified Ford's commitment to performance engineering. From the Group B rally-inspired RS200 to the record-setting Sierra RS Cosworth, each RS model pushed the boundaries of automotive technology. The 2017 Focus RS, with its 350-horsepower 2.3-litre EcoBoost engine, Brembo brakes, Recaro seats, and a mission to endure 30 minutes of track lapping without performance degradation, was no exception. The development of this car was spearheaded by engineers like Tyrone Johnson, formerly of Ford Racing, who brought F1 and World Rally Championship experience to the project. This expertise was crucial in creating a vehicle that not only performed exceptionally on the road but also excelled on the track, with every element, from the redesigned exhaust to the functional aerodynamic components, meticulously engineered for maximum effect.

The All-Wheel-Drive System: The Foundation of RS Handling

Central to the Focus RS's exceptional handling is its advanced all-wheel-drive system, developed in collaboration with GKN. Initially, Ford experimented with a Haldex unit, which provided strong straight-line traction but exhibited understeer at the limit and lacked the engaging feel enthusiasts craved. Attempts to mechanically over-drive the rear wheels with larger tires to compensate for the Haldex's limitations proved unsuccessful, leading to driveline failures due to mismatched gear ratios. This challenge led Ford to develop the innovative Torque Vectoring Rear Drive Module (RDM).

The Torque Vectoring Rear Drive Module (RDM) Explained

The RDM is the technological marvel that significantly contributes to the Focus RS's dynamic capabilities. It functions like a rear differential but incorporates electronically controlled, hydraulically actuated clutches on each rear wheel's output. A dedicated computer, monitoring vehicle sensors 100 times per second, precisely manages these clutches. This system allows the Focus RS to:

• Transfer up to 100% of available power to either the left or right rear wheel within a staggering 0.06 seconds. This is achieved by opening one clutch and locking the other, enabling precise torque distribution.
• Lock the rear axle solid when utilizing the launch control system, ensuring maximum traction off the line.
• Declutch both rear wheels to improve fuel economy during cruising. This is a true AWD system that can disconnect the rear axle when not needed, such as on the highway. The clutches can re-engage within 400 milliseconds when the car detects a need for rear-wheel power, such as during cornering or braking.

The Role of the Clutch in Torque Vectoring

The clutches within the RDM are the heart of the torque-vectoring functionality. They are not a traditional clutch in the sense of engaging and disengaging the entire powertrain like in a manual transmission. Instead, they are multi-plate wet clutches, similar to those found in automatic transmissions or performance differentials. These clutches are controlled by hydraulic pressure, which is modulated by solenoids based on inputs from the car's computer. By precisely controlling the clamping force of these clutches, the system can:

• Distribute torque between the left and right rear wheels. If the car is cornering to the left, the system can send more torque to the right rear wheel, effectively pushing the car through the corner and counteracting understeer.
• Influence the car's yaw rate, making it feel more agile and responsive.
• Enable controlled drifts by allowing the rear wheels to slip predictably, managed by the sophisticated electronic controls.

The GKN-supplied front Power Distribution Unit also plays a role, allowing up to 70% of the engine's torque to be sent to the rear wheels, working in conjunction with the RDM to create the car's signature all-wheel-drive performance.

Driving Modes: Tailoring Performance

The Focus RS offers four distinct driving modes: Normal, Sport, Track, and Drift. These modes, developed with GKN's input, radically alter the car's character by adjusting various parameters, including the clutch engagement strategies within the RDM.

The ability to adjust the electronically controlled shocks independently of the drive mode further enhances the customisation. For instance, one could select Track Mode for aggressive torque vectoring but soften the suspension for rougher surfaces by engaging the shock adjustment button. This level of control, easily accessible even at speed, underscores the RS's driver-centric design.

The Clutch in Action: Handling and Dynamics

The real-world impact of this sophisticated clutch and AWD system is profound. On winding mountain roads, the Focus RS feels incredibly predictable and agile. The engine's low-end torque, combined with the RDM's ability to instantly send power where needed, allows for effortless acceleration out of corners. On the track, the car truly shines. In Track Mode, the torque-vectoring system works seamlessly to keep the car planted, even when pushed hard. If the car reaches its limit, the system can execute a controlled four-wheel drift, making even novice drivers feel like rally professionals.

The Drift Mode, as its name suggests, transforms the car into a drift machine. With a more rear-biased torque split and the ability to manage rear-wheel slip, the Focus RS can execute controlled slides with remarkable ease. This is where the clutches in the RDM are actively working to allow significant slip on one rear wheel while sending power to the other, facilitating the drift. The system is designed to be intuitive, allowing the driver to control the slide with steering and throttle inputs.

Comparison: Focus RS vs. Focus ST

It's important to distinguish the Focus RS from its less potent sibling, the Focus ST. The RS is not merely an ST with upgrades; it features a fundamentally different and more robust mechanical package.

The RS's AWD system, with its sophisticated clutch-based torque vectoring, provides a significant advantage in terms of traction, cornering grip, and overall driving dynamics compared to the front-wheel-drive ST. The ability to precisely manage torque distribution to the rear wheels is a key differentiator, directly enabled by the advanced clutch mechanisms within the RDM.

Frequently Asked Questions

Q1: Does the Ford Focus RS have a traditional clutch pedal?
Yes, the Ford Focus RS is available with a manual transmission, which includes a traditional clutch pedal operated by the driver. The clutch system discussed in this article refers to the advanced multi-plate wet clutches within the Rear Drive Module (RDM) that manage torque distribution to the rear wheels.

Q2: How does the clutch system help with drifting?
The clutches in the RDM are crucial for drifting. In Drift Mode, the system allows for a more rear-biased power delivery and enables controlled slip at the rear wheels. By managing the engagement of the clutches, the RDM can send more torque to one rear wheel than the other, helping to initiate and maintain a drift.

Q3: Can the AWD system be disengaged on the Focus RS?
While the rear axle can be declutched for fuel economy during steady highway cruising, the AWD system is not manually disengaged by the driver. The car's computer manages the engagement and disengagement of the rear axle automatically based on driving conditions.

Q4: What is the function of the Torque Vectoring Rear Drive Module (RDM)?
The RDM is the core of the Focus RS's AWD system. It uses electronically controlled clutches to distribute torque between the left and right rear wheels, improving traction, agility, and cornering performance. It can send up to 100% of the power to a single rear wheel if needed.

Q5: Are the clutches in the RDM wear items like a manual clutch?
While the multi-plate wet clutches in the RDM are designed for durability, they are subject to wear over time, especially with aggressive use like frequent drifting or track driving. However, they are generally expected to last the lifetime of the vehicle under normal to spirited driving conditions. Proper maintenance and adherence to driving modes are recommended.

Conclusion: A Masterclass in Drivetrain Engineering

The Ford Focus RS represents a significant achievement in performance car engineering. Its clutch system, integrated within the sophisticated Torque Vectoring Rear Drive Module, is instrumental in delivering its exceptional handling characteristics. By precisely managing torque distribution to the rear wheels and enabling distinct driving modes, this system allows the RS to excel in a variety of conditions, from daily commuting to exhilarating track driving and controlled drifting. It's a testament to Ford's commitment to pushing performance boundaries and providing enthusiasts with a truly engaging and rewarding driving experience, making the Focus RS a standout in its class.

If you want to read more articles similar to Focus RS Clutch System Explained, you can visit the Automotive category.