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Subaru Forester Generations: Through the YearsHow Does Power Steering Work?
Power steering might just be one of the most overlooked technologies in cars today so we’ll break it down into simple terms.
Moving Two Tons of Metal is Hard to Do
Riding a horse without a bridle is possible but is much more difficult. In the same way, driving a car without power steering is also more difficult. Controlling a multi-ton automobile requires great force and before the invention of power steering, drivers had nothing more than their own muscular strength to turn the wheel. Today, we’re going to dive into everything power steering. We’ll talk about how it works, the different types of power steering, and even a little bit about the future of automotive steering systems.
Hydraulic Power Steering
Before power steering popped up, steering a car that was driving at low or no speed was incredibly hard. The weight of the vehicle and its components required real muscle to move regardless of the powertrain. At higher speeds that force was reduced but automakers wanted to lighten the load regardless of speed.
To that end, automakers began including power steering, an invention from the 1920s, almost 30 years later in 1951. That car was a Chrysler Imperial and power steering was dubbed “Hydraguide.” That name might provide a little insight into how hydraulic power steering works.
To put it simply, hydraulic power steering uses hydraulic fluid along with a hydraulic ram to help the driver change direction. The ram decides which way to move based on steering input and the system is fed a power steering pump reservoir in the engine bay. Between the reservoir and the steering rack, the fluid is pressurized by the power steering pump which itself is driven by a belt attached to the engine.
You may have already spotted a problem though. What happens when you’re not steering the car? Well, all of that pressure simply circulates through the whole system but it does create a parasitic drag on the engine. For you, that means worse fuel economy so engineers came up with another option.
Electric Power Steering
Electric power steering (EPS) gets rid of the parasitic loss by removing the engine-driven pump, the hydraulic fluid, and all of the associated hardware. Instead, an electric motor powered by the battery aids the driver in turning the wheel. The motor typically sits in line with the rack or on the steering column itself. Unlike hydraulic systems, EPS offers engineers the chance to change the amount of assistance provided based on different conditions.
For example, automakers can include a “sport” mode where one feature is that the EPS system provides less assistance. The result offers more feedback for the driver and a steering wheel that feels a little heavier. A “comfort” mode can go the opposite direction by offering more assistance and a lighter steering feel. It’s worth noting that many in the automotive community initially criticized EPS for a lack of consistent steering feedback when it first debuted on an array of production vehicles in the 1990s.
Since that time, it’s come a long way and is widely considered to be as good as hydraulic power steering from an enthusiast’s perspective. A few things are unquestionable though. EPS is more fuel efficient, it’s also much less messy to maintain since there are no hydraulic fluid lines or connections to maintain, and it’s capable of providing more engineering flexibility both with hardware location and with software changes.
The Future Of Power Steering
How much further can power steering really go now that we’ve electrified the process? Quite a bit actually. Tesla’s new Cybertruck is the first production vehicle in history to have no physical link between the steering wheel and the front wheels. That’s because it uses full-time steer-by-wire technology. From a technical perspective, this is still electric power steering but with one major benefit.
In every other EPS system, the electronics are there to aid in reducing the effort needed to turn the steering wheel only. In this new system, that still happens but now, the steering ratio can be dramatically different. For example, at low speeds in a parking lot, a 10-degree turn of the steering wheel can produce a 25-degree change in tire angle.
On the highway though, a 10-degree turn of the steering wheel produces far less change at the tire. That enables a car like the Cybertruck, and any built like it afterward, to employ multiple steering ratios which should improve the driving experience even more.
How much further will power steering go? Only time will tell but don’t expect progress to go backward. The automotive industry will likely see a shift to drive-by-wire electric power steering over the next decade. Just as it has been in the past, we expect every automaker to try and find an edge over the competition. Then we all get to benefit from these advancements in power steering.
