3 Reasons Automakers Switched To Electric Power Steering

As we wait for the highest levels of automated driving to pry the power to steer from our warm, live hands, power steering systems continue to evolve. A novelty when it appeared in the 1991 Acura NSX, electric power steering (EPS) arrived in the 2014 Infiniti Q50 as a true harbinger of the future. Since then, electric power steering has become the common choice for automakers — even though enthusiasts have not necessarily been happy about it.

Until the 1951 Chrysler Imperial came along with its hydraulic power-assisted system, steering a passenger car could qualify as a workout: unassisted steering feels heavy. In a lightweight sports car, or something like a 1951 Volkswagen Beetle that hung its engine over its butt, that might not be a big deal. But in a large front-engine sedan, you felt the heft of the car on the front wheels — especially when parking and turning.

Hydraulic power steering changed the game completely, making it easier to turn the steering wheel and change direction quickly. Those benefits offset their extra weight and the added complexity of the moving parts a hydraulic system requires.

Three-quarters of a century later, automakers are still balancing comfort and complexity, and safety is front and center. The switch from hydraulic to electric power steering factors all of that in, with technology that’s more efficient, adaptable, and plays well with other sophisticated features.

In 1975, Congress established the first Corporate Average Fuel Economy (CAFE) standards, boosting manufacturer fleet requirements from about 13.5 miles per gallon to 27.5 mpg by 1985. It was going to be a healthy 50 mpg by 2031, but somebody with a magic marker recently lowered that to just 34.5 mpg. Regardless, failing to meet CAFE standards can cost automakers billions in fines, if the government chooses to enforce them. And electric power steering helps automakers sidestep potential penalties by making the most of every gallon.

Hydraulic power steering uses a pump, some valves, hoses, and a pressurized cylinder full of power steering fluid to provide the juice that helps turn the steering rack. The pump that makes this all work is powered by an engine pulley. When the engine is running, that pump is pumping — even if you’re not steering. This draw on the engine saps power and fuel. 

Electric power steering systems replace the pump and pulley with computers and motors, and only engage these when steering input is needed. In hybrids and cars with combustion engines, that means no power is being lost to a parasitic steering system, which improves fuel efficiency — by as much as 3%, according to BMW. Plus, EPS parts are lighter than those in a hydraulic system, so there’s less weight to lug. All of that brings automaker CAFE numbers down, and keeps them out of the corporate penalty box. 

Sometimes a bug and a feature are the same thing. With their sometimes-inactive motors, mounted on the steering column or steering rack to dampen things, early EPS systems in some enthusiast cars sucked human senses out of the equation, while hardcore performance people preferred the precision and feel of hydraulics. That’s less of a concern for the everyday driver. Either way, the switch to electric power steering ultimately gives automakers the advantage of adaptability.

With time, automakers have learned how to better calibrate and tune their EPS systems. Companies can filter levels of feel in or out, and make settings selectable, so performance-oriented drivers can choose for themselves how aggressively the electronics behave. Those electronics can be expensive to replace if something fails. On the flip side, there’s no power steering fluid to maintain, and removing pulleys and pipework frees up space.

This enables automakers to adapt for different design needs. In addition to column- and rack-mounted setups, there are also modular EPS systems and rear-wheel steering components. The next frontier ditches the steering-rack mechanical connection completely — Mercedes-Benz is putting steer-by-wire in the upcoming EQS facelift. Without having to worry about designing around a steering column, you can theoretically put the steering wheel anywhere in the car you can run a cable. 

At pub trivia night, hydraulic power steering would be kind of like a trusted, competent teammate who knows the answers, but won’t participate. Electric power steering is more like the friend who not only plays along, but reads the lips of the genius across the room to get the winning information. And is dying to tell you.

EPS integrates better with other vehicle systems than hydraulic power steering does. Its sensors and electronic control unit can monitor things like steering angle, road imperfections, and wheel speed — then communicate the data to other control units in the broader system — from the ABS box that pumps the brakes to the car’s main computer that manages throttle control.

Love them or hate them, advanced driver-assistance features are not only here to stay, but drivers are getting less apprehensive about hands-off steering help. Features like lane-keeping assist, self-driving, and self-parking all communicate with the steering system.

And soon, these may all be legally mandated features. The National Highway Traffic Safety Administration is on track to make automated emergency braking a requirement by 2029. Forward collision and lane departure warning systems are both listed as crash avoidance systems outlined in federal legislation, pending a compliance date. Electric power steering helps automakers enable these features now, and prepare for the future.