Driving a Pickup with Electric Power Steering

Driving a Pickup with Electric Power Steering

What’s it like to drive a pickup with electric power steering? We drove an EPS-equipped Chevy Silverado at Nexteer headquarters in Saginaw, Mich., and we found that, despite the huge technological change, the effects on driving were minimal, but the potential is nearly limitless.

Several weeks ago, we reported on Nexteer's efforts to replace conventional 12-volt hydraulic rack-and-pinion steering systems in half-ton pickups with all-new electric power steering systems in the near future. In today's fast-changing and environmentally conscious times, EPS has several benefits. It offers up to a four percent improvement in fuel economy by getting rid of the losses that come from operating a hydraulic pump, a nearly infinite tuning of steering feel and the elimination of hydraulic steering fluid and hoses.

Tony Dodak, Nexteer's manager of rack-based EPS and premium manual gears, provided us with two late-model Chevrolet Silverado 1500 pickups: one with standard hydraulic steering and the other an EPS engineering demonstrator (not from GM).

After driving both trucks, it’s clear that the changes that drivers notice when EPS finally makes it to their driveways won't be near as dramatic as the technology switch itself. In fact, drivers probably won't notice much difference at all. And, in some ways, it's better than hydraulic steering could ever hope to be.

Probably the easiest way to tell the difference between old and new steering systems was when the truck was parked or moving at low speeds. In a hydraulically steered pickup, when you crank the wheel all the way to one side, you can feel and hear the steering pump strain as it hits the boundaries of the mechanical stops. In the EPS-equipped truck we drove, rather than let us steer all the way to stops and get a clunk, the system gently reduced assistance to zero up to right before the stop. There was no motor noise because there was no assist.

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.

Running on Nexteer's track, we could tell the difference between the hydraulic and EPS steering systems because of tuning differences, not because of component changes. To prove that was the case, Chris Fabien, a Nexteer EPS system engineer -- who's never worked on hydraulic steering systems -- changed steering characteristics as we drove. At the start of our lap, the EPS Silverado's steering felt slightly firmer than when we turned the hand wheel of the hydraulic Silverado. Fabien said it was based on another Nexteer engineer's personal driving preferences.

"Using my laptop” -- connected to the truck's steering system -- “I'm able to change [software] knobs and settings that we use to change how the steering feels," Fabien said. Fabien also showed us graphed curves that represented how much electric steering assist was provided, based on the truck’s speed and steering input. In real-time, the curves changed, depending on how fast the truck was traveling. What we felt with our hands, we could see on his laptop.

"There's a large table data the system looks up again," Fabien said. "It uses that to create the graphs, which represent feel."

That wasn't the most remarkable item. With a click of the mouse, Fabien changed the truck's steering feel as we drove. One moment it felt firm but responsive, then, the next moment, it felt like we were driving a Class 7 utility truck as Fabien switched to a setting that offered much less assist throughout the steering range.

In other words: Need better steering feel? There's an app for that.

EPS Assembly on a Table
Rack-mounted EPS system. It's arranged opposite from the illustrated EPS diagram. The ball screw rack (shown in front) sits inside the assembly.

The demonstrations hammered home the advantage that EPS can give to truck manufacturers, who often spend months agonizing over the steering feel of a new pickup.

With hydraulically steered trucks, engineers may have to drive a truck for days or weeks to get a feel for its turning characteristics. When a change is needed, a valve that controls the flow of hydraulic fluid has to be machined. It's an approach that's both labor- and time-intensive.

In contrast, EPS allows engineers to tune steering feel at the moment that they determine a change is needed.

"We have a crosshair on the computer that we use to follow steering performance over curves as we drive," Fabien said. "It's really great for tuning because when we find a maneuver that feels too light or too heavy, we can immediately drag that point [on the graph] to change the steering feel. It can save weeks of development time."

Dodak compares EPS tuning to an eyesight test. "Is A clearer than B? Is B better than C? We go back and forth quickly to find just the right feel," he said.

Pickup trucks manage much heavier front-end loads than the small cars, where EPS is already used. Can a 12-volt EPS system can handle big weights over the front axle? Nexteer showed as a full-size Cadillac Escalade SUV with about 1,000 pounds of sand sitting over its front end. At rest, without the benefit of forward momentum to help reduce steering effort, we were easily able to turn the wheels in both directions without any sign of strain.

That doesn't mean we could tell the system’s durability from our brief test, but without hydraulic fluid and hoses, there won't be any messy leaks as the system ages. And Dodak said that Nexteer has been testing EPS in pickups for 97th percentile truck owners for up to five vehicle lifetimes or about 1.2 million miles.

Chevrolet Silverado 1500 Equipped with 
Nexteer's 12-volt Electric Power Steering System
Nexteer's Chevrolet Silverado 1500 demonstrator equipped with a 12-volt rack EPS.

Nexteer says that EPS can help improve vehicle safety and stability.

Today’s stability control systems reduce throttle or apply the brakes without the driver intervening to help recover a vehicle when there's a near or full loss of control. EPS can add a third control feature by taking inputs from the stability control system to provide wheel torque and assist to help the driver regain control quicker than they would have with the brakes or engine alone.

There's also the possibility of creating special EPS driving modes to help trucks that are towing or fighting crosswinds. Parallel parking and low-speed maneuvering can be tuned with EPS, and certain rough road conditions can be mitigated before you feel them in your hands.

We're impressed with Nexteer's EPS system and think it's time to say farewell to another legacy technology in trucks. How soon can you expect to drive a light-duty pickup with EPS? One full-size truck manufacturer has plans to offer it on their half-tons for 2011 models and at least three are expected to offer it within three years.

Comments

Thank God a new story for the fan boys to argue over. The pick-up sales chart was starting to get old!

I was skeptical about this technology at first but the more I hear about it and its capabilities I think its a big win. No more power steering hoses, fluid or Whine? 4% fuel economy savings and some probable weight savings to boot? Sign me up, i'm in.

Well it'll be interesting to see if this will be the way of the future of trucks, and it's good to see chev is trying something new with technology...Maybe now they can keep up with the Mighty Blue Oval!!! ( sorry i had to start the argument..lol)

"one full-size truck manufacturer has plans to offer it on their half-tons for 2011 models"

Where did that manufacturer place in the 2008 light duty shootout?

Finally, no more power steering whine whens its -40 out.

Three questions:

i) Which manufacturer will offer it on a 2011 model.

ii) Does it save a few lbs?

iii) When your towing your buddys chevy with e steering, how does he steer if he has no engine/power? With his current model he can steer, albeit its quite heavy. ;)

@ Irwin ; What I got from it was that everything is connected the same as the hydraulic steering just assists with an electric motor instead. So if it goes out you can still control your vehicle.

@Irwin:

1) :-)

2) When you add up all the fluid and parts required for conventional steering, there's a slight weight savings moving to electric.

3) Clay is correct. This isn't drive-by-wire. You still have a direct mechanical linkage to the rack, so if the power goes out you'll be able to turn the wheels without boost.

How much does it cost to replace when it wears out with less than 100k miles on it?

It's got to be going in the 2011 Chevy first since they were using it in the test.

@Dave: Maybe. Maybe not. That's a test truck that Nexteer provided. They also had two other trucks on hand that were not GM brands.

I noticed it uses a belt for gear reduction. How often does that belt need to be replaced?

Is this a clue that it's going in the F-150 first?

The Detroit News says that 90 percent of Ford's vehicles will have EPS by 2012. And the 2011 Mustang currently uses a Nexteer system.


Sounds like a good system. Looking at my current fuel consumption, I'd save 80 dollars a year. I'll take it. Any money that can stay in my pocket is a good thing.

I just drove a 2011 Mustang GT today with this steering system and I was quite impressed with it. It is not something that you would notice unless you were looking for it.

@Paul: According to Nexteer, the belt does not need to be replaced for the life of the truck.

we have an 08 escape hybrid,: which has the electric steering. we really like it. if gm offers it in their pickups for 2011," i'd be interested.

just imagine the fuel savings if all would do away with the belt driven cooling fans and air conditioning.

OK Just came to me, GM 2011 1500 order guides have been out for @ a month. I don't recall seeing anything about this. Which = Its a Ford.

I'm guessing Ford will have it in '11. There are a lot of changes coming to the F150, including some weight reduction.

@ fordmantpw

I keep hearing that. Care to speculate how they acheive those savings? VERY curious as I will almost certainly buy an '11.

Obviously EB will be lighter. What else could they do w/o a major chassis overhaul to acheive any measurable weight savings?

My guess? It will probably be about as reliable as current rack-and-pinion units (which is to say it will rarely make it to 100,000 miles in a light duty truck). No doubt it will have better feel, and will be easier to interface with anti-skid and accident avoidance systems.

Its got to be ford offering it for the 2011 models

They are quick to change things with in the same model year

one to note, they changed to E-Brakes in 2010 from 2009

Why not Electric Steering?


.... just speculating ;)

electric steering is just more B/S to go wrong rack & pinion and p/s boxes has been working for years people are just getting too LAZY to take care of their p/s systems if you keep p/s fluid in the reservoir you wont have a problem......
WTF is next electric brakes

WTF happens when that belt breaks......are you S.O.L.

why would it be more bs to go wrong? it looks a lot more simple than a hydraulic setup.

It know its not on the same scale but there are quite a few brands of ATV's out there (Mine being a Yamaha Grizzly) and they work beautifully and most without failure! Both these systems are very similar and and should work beautifully in a light duty pickup application!

@Irwin

I honestly don't know. I could speculate:
1) Some lighter-weight, but stronger (per lb.) materials in the frame
2) Lighter engines (aluminum vs. iron). Not really sure what else
3) Electric Power Steering :)

Meh i want to see if they fail just as bad with eps on the trucks as they did with the cobalt.

@ Jay Murch

I think you meant to say change to e fan, vs. e brakes?

@ fordmantpw

You really think they' make major mods to frame after 2 years?

Short of that the only thing would be composite materials in place of fenders etc... But that adds cost.

2.5 months we'll know.

Won't manufacturers phase this in?
Start with 4x2's 1/2 ton
Then, the subsequent year move to 4x4 1/2 & 4x2 3/4 ton
Next 4x4 3/4 ton & 4x2 1 ton, etc.

@Irwin
It wouldn't surprise me if ford made some mods to frame material. Ford has been very agressive latelly with adding features and keeping vehicles fresh. Body panels was another thought...I was thinking maybe aluminum??

You're right though...we'll know in a few months. :)

@George
Doubtful. I say it goes full bore on 4x2 and 4x4 half tons, since they use similar (if not identical) steering due to having IFS. I don't think we'll see i on 3/4-1 ton for a while though...I don't think any of them use rack and pinion steering, which I think is a requirement for EPS.

@ mike levine if they all go through this same company is teh steering feel going to be the same of would each company do there own.
As far as going to e-steering I dont see what the big problem is, with efi you cant go anywhere with a dead battery or bad alternator anyway.

@bobsled80: It's unlikely that steering feel will be identical between trucks, even if they're using the same or similar hardware. As described in the story, it's very easy for truck manufacturers to customize feel based on what they determine to be the right characteristics by flipping a few bits.

quote - In other words: Need better steering feel? There's an app for that.

At the flick of a switch many sports cars have different states of performance tuning.
The Raptor has different performance modes at the flick of a switch.
I bet we will see the same thing with e-assist steering down the road.

Come on guys! time for a new article.. Have you seen the new western edition pack Ford is offering on F250's?

@Jordan: Check the upper right part of the front page. The latest news is up there with many other stories.

I find it hard to believe that electric power assist will increase fuel economy by 4 %. The PS pump puts nowhere near the engine load of a A/C compressor and that only decreases fuel mileage by 1/2 to 1 mpg.

Thanks Mike.

my only beef is that it uses a belt inside. Shouldn't it use a chain or a gear instead? Besides if it is sealed, you shouldn't have to buy grease or fluid for it but still have better durability than that belt i saw in the diagram. I mean what would happen if that belt (i assume rubber) snaps or wears out? Think of the costs!?

This system is in the 2011 ford f-150 and there is a Q-200 release that states that these truck can not be equipped with snowplows because of the high electrical demand on the power system it could damage the electric motor in the power steering unit.

I really think electric power steering systems will phase out traditional hydraulic power steering systems within the next 10 years. It is the way to go. Lighter, less power draw from engine, cleaner etc.



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