Electric vs hydraulic power steering
Power steering is a technology that all drivers take for granted. Before the advent of this technology, the only thing that helped you turn the steering wheel was your own strength. Power steering is now offered in several different ways; hydraulic, electric and, more recently, drive-by-wire. Read on to learn more about power steering, its history, reliability and repairs, and how each type affects a car’s driving dynamics.
What is Assisted steering?
In almost all vehicles, there is a steering column that connects the steering wheel to the wheels through a system called a rack and pinion. Rack and pinion steering transfers driver input to the wheels. This system worked without any electrical assistance, it did on production cars until the early 1950s.
While the first commercial use of power steering was in the 1950s, the technology was first patented 75 years earlier, in 1876.
Why was power steering invented if power steering worked fine then? While driving without help works, it is not always easy. When the car is stationary or moving slowly (think in a parking lot or turning at a traffic light), you have to overcome much more friction than when they are turning. This can make the steering wheel very difficult to turn. Power steering gives you a hand, making it easy to turn the wheel no matter what, where or how fast you’re driving.
Type of assisted steering
The power steering is hydraulic, electronic or electrohydraulic. Drive-by-wire is a variation of electric power steering.
Hydraulic assisted steering
Hydraulic power steering (which simply means fluid moving under pressure in a small space) uses compressed fluid to assist the driver when turning the steering wheel. The fluid is pressurized by the power steering pump, which comes from the engine.
A rotary valve controls the flow of pressurized power steering fluid to one side of a hydraulic piston, depending on which way the wheel is turned. Hydraulic fluid assists in turning the wheels, which means that the required input from the driver is reduced to a minimum.
Pros and cons of hydraulic power steering
Hydraulic power steering has been around for a long time. It is a well understood and designed concept. If you ask an enthusiast, you might hear that hydraulic steering has better “road feel” or a more physical connection to the road.
However, hydraulic steering is not without its flaws. These systems are more complicated as they require the use of an engine driven power steering pump. More components increase the likelihood of failure.
The hydraulic fluid pressurized by the pump can also become contaminated. In some vehicles, periodic fluid changes are required. Although the intervals between changes are usually much longer (50,000 miles or more), it is still a maintenance item that electric power steering systems do not need.
Electric assisted steering
Electric Power Steering, or EPS, eliminates the power steering pump, fluid and lines from the system. Instead, an electric motor fits into the steering column and provides the necessary boost to facilitate steering. This type of steering system communicates with the ECU (engine control unit) via sensors, allowing the system to adjust the steering based on conditions such as vehicle speed.
Pros and cons of electric power steering
Since electric power steering doesn’t rely directly on the engine (the engine gets power from the alternator, only when the wheel is turned), it can contribute to better gas mileage. EPS systems are also less complicated than their hydraulic counterparts, less prone to problems and require less maintenance.
When EPS was first introduced, many drivers complained about the lack of steering feel or feedback. Early EPS systems were disconnected from the road, often described as “sleepy”. Feedback from EPS systems has improved significantly since then. Companies like Porsche now include electric power steering in their high-end sports cars like the 911.
Other types of assisted steering
There are currently two other types of power steering that are used in vehicles.
Electrohydraulic assisted steering
A combination of the two technologies mentioned above, electro-hydraulic power steering uses an electric motor to drive the hydraulic pump. This allows power steering fluid pressurization to not be directly tied to engine rpm, improving steering feel and fuel economy.
Assisted steering by cable
Drive-by-wire, or steer-by-wire, is a relatively new technology that completely eliminates the traditional steering rack of the car. Instead, steering input is sent to the wheels electronically. Relative to other power steering systems, steering by cable is used in very few vehicles.
Assisted steering service at Alex’s Autohaus
European vehicles often feature the latest and greatest technology, and power steering is no exception. If you’re having steering problems with your BMW, Mercedes, Land Rover, Audi or other European vehicle, give us a call or schedule an appointment online today!
