Electric Power Steering is Coming to Light Duty Pickup Trucks

Electric Power Steering is Coming to Light Duty Pickup Trucks

Pickup trucks are rapidly changing to become more fuel efficient. But it’s not just new powertrains and aerodynamics that are pushing the limits of frugality. Even the way you steer your truck is about to change.

Executives from Nexteer Automotive, a driveline manufacturing spinoff from General Motors and Delphi, say conventional 12-volt hydraulic steering systems are about to be replaced in half-ton pickups with all-new electric power steering systems.

"We expect that all three domestic [truck manufacturers] will converge to a 12-volt rack EPS architecture within the next three years or so," said Mike Richardson, Nexteer’s vice president of engineering and global steering business line.

Until recently, EPS systems were available only in smaller cars and crossovers because the components weren't strong or efficient enough to meet the higher front axle steering loads of pickup trucks. Only GM's 2009-10 Chevrolet Silverado and GMC Sierra Two-Mode Hybrid pickups offered EPS because their powerful (and unique) 42-volt electrical architectures provided enough energy to support the feature.

Whereas a hydraulic power steering system uses an engine-driven pump and pressurized hydraulic fluid to help turn a truck's wheels and reduce driver effort, EPS replaces the hydraulic pump and fluid with an electromechanical motor-driven connection to the steering system.

And whereas a hydraulic steering pump always requires power, even when the truck is traveling in a straight line, EPS requires power only during steering maneuvers, which helps make the vehicle more fuel efficient.

"In general, there's about a 4 percent improvement in fuel economy," said Tony Dodak, Nexteer's manager of rack-based EPS and premium manual gears. "[In a pickup] that equates to around 0.5 to 1 mpg depending on the vehicle and the mileage of the powertrain."

Several innovations have made 12-volt EPS in a pickup possible. The first was the conversion of half-ton pickups from traditional recirculating ball steering linkages with greater leverage capabilities to handle high steering loads (they're still used in almost every heavy-duty pickup) to rack-and-pinion systems, which offer better feedback to the driver.

Nexteer's EPS setup uses a so-called belt and ball-screw system, where the electrical motor turns a belt that runs to a ball screw that provides direct assist to the rack-and-pinion gear set.

EPS Diagram
This diagram shows an enlarged cutaway of the EPS motor assembly (bottom middle) attached to the steering system on the passenger side of the vehicle. The ball screw portion visible (top left) under the driven (large) pulley and extending out is the rack. The small pulley is attached to the driveshaft of the electric motor. A belt wraps around both pulleys and acts as the first stage of a two-stage gear reduction that makes EPS possible in a light duty pickup. The second stage is between the ball nut and ball screw.

The second innovation was the development of a two-stage gear reduction system — which eases the load on the electrical motor while still delivering high enough torque to help with steering duties in heavy-vehicle applications — coupled with high-efficiency brushless electric motors.

But perhaps most important innovation was measuring and metricizing the feel of hydraulic steering systems so that a similar feel could be replicated and potentially improved with EPS. Early EPS-equipped vehicles have been criticized for feeling numb and disconnected in drivers' hands.

"We've spent the last 12 to 15 years converting our competencies from hydraulic-based steering to electric," Richardson said. "Now, OEMs can’t tell the difference whether they’re driving an electric-powered steering system or hydraulic. Some refuse to do blind rides. That's really a milestone. The industry has gotten to the point where you can’t tell the difference."

It's important to note that EPS is not drive-by-wire, which removes direct mechanical linkages from the steering wheel to the drive wheels. EPS provides power assistance while the truck is still controlled from the steering column to an intermediate shaft to the rack-and-pinion gears and to the tie rods at the wheels and tires. If you lose power assist, you can still manually turn the wheels.

In some cases, EPS systems can go one better than conventional hydraulic systems by increasing or decreasing power assistance and steering feel based on specific speed and driving conditions. In high-wind situations, extra torque could be automatically applied to help keep a vehicle straight on the road, a feature that could benefit pickups towing trailers. It could also help half-ton pickups parallel park themselves with minimal assistance from the driver.

But EPS also has a few disadvantages in its current state of development.

Nexteer depends on software to provide just the right level of power assistance and feedback that's tailored and calibrated to the model and powertrain available in a pickup. A buyer customizing an EPS-equipped pickup with new wheels, tires or suspension modifications could find the truck behaving or feeling differently from what’s expected. It's just one of several factors we've previously cited that could limit how much you can modify your pickup in the future.

Future EPS with more intelligent software could be the answer, but it won't be available in first-generation EPS systems in half-ton pickups.

"Right now, the system has a lot of margin for change at the vehicle level. It can allow for different adaptations and still be OK for performance," Dodak said. "Eventually, manufacturers may add custom features that we could apply as an aftermarket tool. We could provide interfaces in the future for highway tuning versus sporty city tuning."

EPS also won't work in HD pickups with recirculating ball power-steering systems. The parasitic load is too high for a 12-volt electrical architecture to provide enough torque. One possible solution to this issue is to apply some of the lessons learned from EPS to provide more intelligent hydraulic power assist that can vary boost levels based on driving conditions.

It's not often that we see this significant of a mechanical change in pickups. It could be compared to the switch from carburetors to fuel injection. But one thing is certain: EPS is coming to half-ton pickups and, ready or not, you're going to get your turn to steer your truck with this technology.

Comments

Not being able to put custom wheels, tires, and a lift on your truck is going to be a huge issue with aftermarket manufacturers. What are they even thinking by not fixing that problem before they make the big push to get this system into half tons.

Do this,and maybe experience the Toyota Corolla lane wander issue...

"In some cases, EPS systems can go one better than conventional hydraulic systems by increasing or decreasing power assistance and steering feel based on speed and driving conditions."

97+ C/Ks have this: Variable Effort Steering (VES). It's been around for a long time and IS available on conventional hydraulic systems.

Ford also has this: they call it variable assist power steering and first introfuced (VAPS) on the 1988 Lincoln...

I would suspect that one of the reasons Ford made the Raptor was to offer a truck that would work with all the new technology, most of which, is being mandated by the government.
There was a story posted a while back that the new laws mandating stability control would hurt the aftermarket industry. If the lift and tires buggers up the stability control the owner or the aftermarket company would be libel in a crash. Same could happen with electronic steering assist. I can see more aftermarket goodies being sold with a big notice - "for offroad or closed course use only". That would transfer liability to the owner of the truck.
At least these systems are NOT drive by wire.

Given all the makers have to do to produce small MPG gains, I shutter and wonder when Big brother will start to 'try' to control what we do to the trucks after we buy them.

They add lower airdams, e power sterring, you name it and we go add a 2" leveling kit and heavy 10 ply rubber and kill it all. So in effect what have the expensive changes accomplished in real world conditions? Zip. Its all such a farce.

Even the "29" mpg trucks with 3.08 rear ends. First winter guy puts on real rubber and its with the rest of the pack. (with no low end)

As a Ford guy I'd be happy with e PS jsut to get rid of the Ford PS whine @ startup when its -40 in winter!

@POWERKID

Though there is a significant MPG loss with a lift and bigger tires, the truck with the MPG features will still do better than the lifted truck w/o them.

The Farce is that most of the people who bitch about gas prices (especially when they were near $4) are the same ones who dont put in the individual effort to help lessen the problem.

Gee, the ATV folks kinda beat the auto/truck manufacturers to the punch on this one by years!

For recirculating ball type steering gears they could have an electrically driven hydralic pump. Simple, but i doubt the extra cost would be worth it. The belt seems pretty iffy to me.

@Tim and Tom: My apologies about my poor phrasing in the opening sentence of that paragraph. Hydraulic steering pumps in trucks haven't offered the scenario-specific, fine-grained boost assistance that electric steering promises to be able to using software and discrete moment electric motors.

Later this month I'm going to do a side-by-side drive comparison of the two systems in identical full-size pickups. Stay tuned!

Good to see, companies are trying to get every bit of non efficent tech out of these things.

Since we are on the subject of electricity, what hurdles would you have to clear to start putting electric water pumps in trucks? Is it even feasible?

@No Big deal, I have already owned a 2005 model car with EPS, so it's not new to auto manufacturers either. Just new to pickup trucks, where fuel economy has only just started to become a big deal.

I see Toyota Tundra has this kind of set up...

They do these little things to try to bump up economy by one or two percent but all it seems to do is bump up the price, Look at the Dodge Ram they brag about its arodynamic and its more efficiant powertrain, but in the real world it still only gets 13MPG, or the same as what it was ten and fifeteen years ago.

Great. These systems have been trouble in just about every vehicle they have been installed in so far.

Nooo... Not another stupid kind drive-by-wire stuff, that kills the car-feeling, feedback while driving!

The EPS unit on a Ford Edge retails for $1,800.
Steering feel is great on that vehicle.

I saw a new technology called "Direct Link Steering" (DLS). This system features no complicated hydraulics or electric components. Just the wheel and your two arms. Great feedback...you can feel it in your arms even after you're done driving!

@JEFF

The reason the ram gets only 13 mpg in the "real world" is because people in the real world drive like idiots. IDIOTS!!!!! If you drive more with your brain and less with your foot, you can easily exceed the EPA mpg ratings. This is the typical american attitude, instead of putting in the effort to drive more sensibly, we will sit back on our lazy asses and depend on others to fix the problem. It's like the guy who is 200lbs overwt, he doesn't want to diet, he doesn't want to get off his fat butt and exercise, all he wants is someone to give him a magic pill to make him skinny.

so, besides an improvement in fuel mileage, does anyone see a change in size? it still looks just as big as hydralic assisted brakes.

Oldie has the best comment. I think cars and trucks should be more simple like they used to be.

Really an interesting post.Thanks for an insightful post.It’s my first visit.I like very much your way of presentation.Keep up the good works and hope you post again soon.

Electric Power Steering is replacing hydraulic power steering in many new vehicles today. One of the advantages of electric power steering is that it eliminates the power steering pump. This improves fuel economy while also eliminating the weight and bulk of the power steering pump and hoses.

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