The Important Differences In Approach To Power Steering for EVs (& All Vehicles)
Steering is an underrated thing in cars, especially electric cars. We can get so worked up about horsepower and torque numbers, range, charging speeds, and 0-60 times that we forget to think about other things. All of the big numbers we see are basically connected to the accelerator and brake pedals, but it’s easy to forget about the thing we use the most: the steering wheel.
In this article, I’m going to share a quick video, then go through the history of power steering for electric vehicles. It has been an interesting challenge, first for DIYers and then for manufacturers. They all have a certain feel they’re going for, and getting there can be a pain.
First, let’s look at a recent video at Engineering Explained, where Jason goes through the important considerations for each type of power steering system, along with how they work. He does this while driving a McLaren with a less common type of steering system:
No Power Steering (Manual Steering)
If we’re going to talk about the history of power steering, we have to start at the very beginning: no power steering at all!
One of my favorite cars I’ve ever owned was the Pontiac Fiero. I had a 1986 with an automatic when I was pretty new to driving, and I had a 1987 with a manual (that car was infinitely more fun, even though the third gear synchro was worn out). One of the really cool things about the car was its complete lack of power steering, which was a real oddity in the 1980s.
I say it was really cool because at normal driving speeds in the city or on the highway, you really don’t need power steering at all. You get a very direct feel for the road through the steering wheel, and you get real resistance. It can be a bit rough at times, especially on roads that induce vibrations, but most of the time it’s like a minimalist running shoe (I like those, too). You really feel connected to the road.
The downside that most people just aren’t willing to live with is that steering is difficult at lower speeds, especially in parking lots. With no power steering, the driver must provide all of the power. Being intersex (here’s a decent explanation of what that means), my arm strength is naturally strong by female standards, but weak by male standards. For that reason, I’m one of the few women who really like manual steering. Most women just can’t live with it, because it can feel borderline impossible to navigate parking lots and parallel parking.
Power steering was often marketed early on with women in mind (because the stronger man wants his wife to be able to drive the car), but if the men were honest, they also would tell us they appreciated things just being easier. There are still a few old guys around who tell people that every car they’ve ever driven had power steering, because they provide the power (this is usually said while flexing arm muscles).
Whatever the reasons for inventing and buying power steering, it’s included in all but a few rare cars these days, even the vehicles most loved by men. Pontiac decided to not install it in the Fieros I had because the engine was located in the back, and running the long hydraulic lines from a power steering pump to the front would have been problematic, expensive, and possibly dangerous. Plus, the car was originally designed for maximum efficiency, and a power steering pump lowers gas mileage.
Hydraulic Power Steering
In that last paragraph, I got a bit ahead of myself. We need to discuss hydraulic power steering real quick. In all cases, there’s a power steering pump that must be turned to provide hydraulic pressure to the power steering fluid in the system. This hydraulic power is then used in the steering rack to make things easier for the driver.
In all but the newest hydraulic systems, the power steering pump is an engine accessory, and thus was driven by a pulley attached to the engine’s crank, along with things like the water pump and alternator.
The downside is that primitive power steering systems robbed the driver of most of the road feel, regardless of what the marketing departments claimed. The simplest systems gave more assistance at higher speeds, and less assistance at lower speeds — basically the opposite of what is actually needed. Later systems provided constant assist power across all engine speeds, but that is problematic because giving enough assist at parking lot speeds means far too much for highway speeds. Further improvements led to variable systems that could lower the assist at highway speeds.
Beyond providing for needs at low speeds, there’s another challenge: personal taste.
Some people, particularly luxury car drivers, want a more disconnected feeling from the road. Light and easy steering, with only a little feedback, gives them that. Others want assistance at lower speeds, but no assist at all for higher speeds. Even for the buyers of a particular car, tastes can differ, and hydraulic systems give very little room for customization.
The Challenge Of Power Steering For EVs
People doing their own EV conversions in garages had a particularly hard challenge with this. In a time when most cars came with a power steering pump attached to the gas engine, getting rid of the engine leaves the vehicle with a power steering rack that lacks power, which is harder to turn than a manual rack.
To get around this, the DIY crowd and professional conversion shops had several paths to power steering. Some would attach a small electric motor to the power steering pump (like they did with the AC compressor), and mount that setup on a custom mount under the hood. This provided power steering just like the car had before, but at the cost of range because the motor runs all the time (McLaren uses a better version of this method for some of its gas-powered sports cars, as the video above shares). Some people would swap in manual steering racks, if one were available that would fit.
Later, they did the same thing most manufacturers are doing now, even with gas-powered cars.
Electric Power Steering
Getting rid of the hydraulic power steering system completely makes a lot more sense. By switching the power steering out for one that only provides power assist when it’s actually needed, you save a lot of power for EVs and EV conversions so you don’t lose a noticeable amount of range to power steering’s parasitic load. It’s a real win-win.
Even for gas-powered cars, electric power steering makes a lot of sense because you’re getting rid of a complex system and replacing it with one that has fewer moving parts. You also get better performance and efficiency by not having that power steering pump constantly dragging down the motor. This helps the car get a better fuel efficiency rating, and thus helps the manufacturer meet things like CAFE standards, carbon reduction goals, etc. Once again, win-win.
You also get the advantage of customizability. The programming for the little electric power steering motor can be changed, often in a vehicle’s settings menu, for a lighter luxury feel or for a more raw and sporty feel. Cheaper cars, like my Nissan LEAF, don’t offer this, but better vehicles like a Tesla let you decide how much help you want from the system.
The downside is that electric power steering systems dampen the finer road vibrations a bit, which is why the McLaren uses an electro-hydraulic system with variable motor speed. Outside of the track, though, most people don’t find the tiny vibrations useful or desirable, so electric power steering is still the best solution available.
Featured image by Tesla.
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