New System Description

New System Description
With a conventional power assisted (hydraulic) steering system, a belt driven pump provides pressure to the control valve which is integral in the power steering rack. When the steering shaft is turned, the control valve provides pressure to assist (decrease effort) in turning the steering gear.
On some BMW vehicles, this control pressure is reduced by increasing vehicle speed via an electronically controlled bleed off valve (Servotronic). However; hydraulic power assisted steering systems utilize a reservoir, hydraulic fluid, pump, hoses/lines, cooler, hydraulic valve/steering rack, Servotronic valve, purpose built steering shaft and column.
Electric Power Steering (EPS)is used for the first time by BMW in the (E85) Z4. It provides the typical BMW power assisted steering characteristics and "feel". The EPS is a very direct, sporty steering element with a change over between normal and "Sport" mode by the Dynamic Driving Control (Sport) button.
The EPS differs from the conventional hydraulic power assisted steering system by utilizing electrical electronic components to provide power assisted steering while retaining a complete mechanical connection. The EPS is a "dry system", the hydraulic components and oil are not required.








The programmed EPS control functions are influenced by vehicle speed and provide additional benefits regarding steering tuning, absorption adjustments and active steering return characteristics.
The EPS system includes:
1. EPS Control Module
2. EPS Electric Motor
3. Lower Steering Column
4. Steering Rack
5. Steering Gears
6. Steering Angle Sensor

The advantages of EPS are:
^ Less maintenance and assembly
^ Improved driving dynamics
^ Increased comfort
^ Increased driving safety
^ Weight reduction
^ Increased environmental compatibility
^ Less power consumption

Improved Driving Dynamics:
^ The EPS Electric Motor provides good power assisted steering control characteristics.
^ Active return to center.
^ Switchable steering characteristic (Dynamic Driving Control).
^ Use of light weight sport steering wheels (1 kg less than other steering wheels).

Increased Driving Comfort:
^ Decouplesunnecessary steering oscillations (from road disturbances) while maintaining relevant road feel information (different road conditions) to the driver.
^ Speed dependent steering assist force (parking vs. high speed driving).

Increased Driving Safety:
^ EPS provides a direct mechanical connection to the steering gear, conveying direct road feel.
^ Speed dependent steering actively absorbs left/right roll.

Increased Environmental Compatibility:
^ Reduced fuel and engine power consumption
^ Leak free dry system