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4x4 Electronic Performance Systems - Then & Now

Posted in How To: Electrical on October 1, 2005 Comment (0)
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Photographers: Courtesy of Toyota Motor Sales USA

Five hundred issues ago, everything was a trade-off. By increasing suspension height, you gained ground clearance-but your 4x4 leaned like a drunken sailor every time you drove around a corner. The quick steering you wanted for the trail made the vehicle twitch and dart all over the highway. Tires that delivered better traction melted away in no time. You could get much better traction by adding lockers, but then you couldn't steer. If you set up the throttle for nice, light response, it tended to surge in low-range.

Now, all those trade-offs can be practically eliminated. Computers have radically changed the design envelope. The precursor system, ABS, was ho-hum at first, and late making its way into 4x4s. But then manufacturers started developing finer sensors and better coordinated logic. Those systems, originally developed for on-road safety, have now become off-road performance systems. What was merely amusing has now become amazing. And we haven't seen the end of it yet.

Take traction. Early traction control systems required wild wheelspin to kick in, throwing rocks and burning tires. Now we see systems that kick in with just the smallest amount of wheel slip. Working in the background, electronic systems can flash differentials through lock-and-unlock modes, managing as many as three locking diffs at once. With front, rear, and center diffs clicking in and out a hundred times a minute, working the brakes to supply torque to any individual wheel as necessary, an unmodified 4x4 can crawl steadily across steep, slippery terrain. As long as any one wheel has traction at any given instant and throttle is applied, the vehicle moves forward.

With no wheel slip, milder tires can be used. So you tear up the trail less, your tires last much longer, and you can live with the tire on pavement. You are driving elegant, courtesy of modern electronics.

The latest systems, such as Toyota's TRAC, work using magnetic sensors on the wheels that count how much the wheel is rotating, and whether it is moving forward or backward. With that information coming in, a processor checks to see what you are doing with the throttle and transmission-in effect, it determines your intentions-and locks or unlocks a diff, brakes a spinning wheel, or selectively applies ABS pulsing. The instant intervention is no longer required, and the computer flashes back to a routine mode.

We hate to say it, but it's true: no matter how many selectable lockers you have or how fast your fingers might be, there is no way any human being can take similar actions, or make better decisions, on the fly. You cannot manage three locking diffs and wheelspin at all four corners, locking and unlocking, braking and releasing, all in the space of 1 inch. But the computer can do it all day long.

Traction control also reduces the need for extreme gearing. Good, low gearing to crawl slowly upward and roll slowly downhill also results in a 4x4 that takes three gears to reach 25 mph and screams bloody murder on the highway. That reality spawned a wide variety of overdrives, underdrives, and other complex mechanical solutions. Those things will work, but also induce other complexities, such as too-short driveshaft length and driveline component adapter availability.

Now, with electronic traction control and an automatic transmission, uphill progress is slow and relentless, with minimal wheel slip, if any. On the downhill side, another electronic system controls each tire individually for a slow, progressive descent.Meanwhile, your on-road driveability is not compromised.

The Range Rover Sport is a high-performance touring SUV, tuned for the street with low-profile tires. Because it has an electronic air suspension, electronic traction control, throttle control, and electronic swaybar disconnects, the Sport can walk up Wipe Out Hill at Moab without spinning a wheel.

There are also electronic systems that add the kind of performance that nothing mechanical can address. Take hillclimbs. You're nine-tenths of the way up Suicide Hill when you drop two tires into holes dug by the last guy who just wouldn't give up. Now you're bouncing, kicking up dust, and you have to lift the throttle and set the brake. A hill start from here would be touchy. So you decide to back it down for another try, and looking back, you notice you're just one slip away from a real-world rollcage test that ends up as a video on Four Wheeler TV.

If you had one of the two systems Toyota and Lexus include on the LX470 and other 4x4s, you could breathe a whole lot easier. One system, called Hillstart Assist Control (HAC) automatically holds the vehicle in place to regulate roll-back. So you can pause to try a different line without rolling back. If you do have to back down, another system called Downhill Assist Control (DAC) will regulate downhill speed to 2 or 3 mph. Just put it in Reverse and all you have to do is steer. We had a chance to test the Toyota system on a very steep hillside that started out as dirt and gave way to loose rock. It wasn't a long hill, but it was a very steep, jumbled mess of loose dirt and rock. We were surprised at how well DAC worked, especially in Reverse.

Before electronically adjustable suspensions, a setup for reasonable on-road manners meant there would be no articulation on the trail. Antisway bars limited suspension droop. With KDSS, a Lexus GX470 suspension droops as if there are no antisway bars at all...

A number of manufacturers have added similar descent control systems into their latest SUVs, some with more capability than others. One system we particularly like appears in the Land Rover LR3 and Range Rover Sport. The Land Rover system, which they call Descent Control, can be adjusted for rolling speeds on the fly, all the way down to 1.6 mph.

Another Toyota system we tested is called VDIM, for Vehicle Dynamics Integrated Management. It's an advanced handling system that integrates brakes, steering, electronic traction controls, throttle, and engine management to prevent skidding. So let's say you're blasting down a long, unfamiliar dirt road. There are little dips, patches of loose gravel, occasional turns, and sometimes a washout obscured by vegetation or terrain. You come up on one a little too fast and whoops! You're sideways, heading for the ditch.

...The value of sway-bar disconnects has long been known. But now the disconnects are electronic, actively managed by a computer. The advantage in suspension travel, about 4 inches, makes a huge difference when rockcrawling.

With VDIM, the ability to correct a skid is practically a religious experience. We tested it on a loose-gravel road at Toyota's Arizona Proving Grounds. Without VDIM, we skidded all over the place, even at 20 mph. With VDIM, we headed deep into the corners at 35 or 40. Just when you know you're going to die, the truck slows a bit, comes around and goes exactly were you steer it. One guy referred to it as the "Hand of God" system, because what it did seemed like a miracle.

The system works by looking at everything-steering angle, yaw rate, throttle position, and more-and figures out what you are trying to do. And then it organizes a fix. It uses selective braking-maybe just the two brakes on the driver side of the truck, for example-to correct side drift. It might also influence an electronic variable steering system to slow the steering rate to reduce skidding, and tell an electronic "brake by wire" system to maintain traction via ABS pulsing. All of these responses occur at the proverbial speed of light, and are practically transparent to the driver. With remarkably little loss of speed, you steer back onto the road and accelerate toward the next corner, where hopefully you take a decent line this time.

FYI: If it sounds like dirt-roading is fun with VDIM, we admit it is.

High-speed, emergency lane-change tests at the Toyota Desert Proving Grounds outside Phoenix, help illustrate how Toyota's Vehicle Dynamics Integrated Management (VDIM) system works. On a slippery surface, like a graded road, VDIM is uncanny beyond rational comprehension. It uses brakes, steering, and an array of sensors to keep a 4x4 on the road well beyond reasonable speeds. It also works on pavement.

Yet another emerging performance enhancement adds (or subtracts) suspension articulation. There are several kinds out already. Toyota calls its Kinetic Dynamic Suspension System, or KDSS. KDSS appeared on the Lexus GX470 in 2004, which pretty much won Four Wheeler of the Year testing because of it. When our Ned Bacon built project TraiLex, he made a point to keep all KDSS functions intact, because it works. The system adds about 4 inches of articulation, an improvement of 22 percent versus the standard suspension. It also works with the electronic shock control system, continuously changing damping in response to road conditions and driver input.

Land Rover has a similar system on the Range Rover Sport, which they call Dynamic Response. It has different hardware, kind of like a sliding sleeve system in the middle of the axle, but the effect is to add articulation off-pavement and limit body roll on pavement. With Dynamic Response, we drove the new Range Rover Sport, a high-speed touring SUV with 40-series tires, up Wipe Out Hill at Moab.

Jeep has a system about to come out they call Dynamic Handling (DHS). It uses hydraulic-controlled stabilizer bars that can be decoupled, except when they are needed to improve cornering performance. The system checks steering angle and two lateral accelerometers that detect body roll. Then actuators pressurize the bar links as required.

Electronic descent control is not new, but it is getting better. It's hard to see how steep this hill really is, and how slippery. Using Toyota's Downhill Assist Control (DAC), we rolled down with no drama. It works even better in Reverse. Another great adaptation is called Hillstart Assist Control (HAC), which allows you to stop and start on a hillclimb without spinning a tire or rolling back. If you lose grip, you can pause, pick a new line, and move forward.

In the future, we can expect to see these performance-enhancing systems on much lower-cost 4x4s. We could see it in the 2006 model year, when the new Toyota FJ Cruiser arrives, and probably the next Land Rover Defender. Eventually, Jeep is going to realize electronic traction control can even improve the Wrangler.

If these developments seem boggling, it's because they are. The entire analog world-TV, telephone, video, automotive-is moving toward digital systems. Since these systems are hard to see and understand, they initially threaten our sense of self-reliance. As with ABS and fuel injection, the temptation is to discount technologies we don't fully understand. But in the end, we will drive differently, and as with Project TraiLex, we will modify differently. Time will show that these systems bring clear performance, safety, and operating advantages. It won't take another 500 issues for that to become crystal-clear.







* In the wake of disappointing third quarter sales, Toyota General, the world's largest automaker, announces it will sell off its struggling Buick and Pontiac divisions to arch-rival Nissan-Benz for $124 billion. In other news, Toyota announces a joint venture with MitSuzuki Motors to produce engines for the Hummer H9, a 500hp ATV that debuted in concept form at Tokyo in 2045, as well as plans to expand production of its popular Chevrolet Huron/GMC Juneau/Isuzu Apex/Saab 24-7 midsize AWD hydrogen sport-wagon that debuted last year. No word is forthcoming on the future of the Buick Shasta following the Nissan-Benz acquisition.

* Ford Motor Company CEO Bill Ford VI announces final plans for rollout of the company's hydrogen-powered vehicle line. "We've had a few setbacks," Ford admits, "but we are now on target to be fully implemented by 2050 at the very latest. Our continued commitment to a greener world demands it." In related news, Ford officials announce plans to begin production of the Lincoln Leviathan Mark VII SUV, based off the popular Ford Colossus V-16 platform.

* HondaChrysler Corp. announces that the company will cease production of its flagship Jeep Liberty SUV after years of flagging sales. "The Liberty's had a great run," says outgoing Jeep division president Nick Cappa, "but nothing lasts forever, and it's time to take the Jeep brand in a new and innovative direction." Rumors circulate that the Liberty's replacement in the Jeep lineup will be a midsize hydrogen AWD sport-wagon currently code-named Choctaw.

* In other news, HondaChrysler announces the release of a limited-production "Robin Stover Signature Edition" Dodge Bighorn 2500 pickup to honor the legendary Baja racer and crew chief on his 70th birthday. The truck will be powered by a twin-turbocharged, diesel-propane 12-liter CumminSuzu I-6 that is said to produce 1,250 hp and deliver 50 mpg.

* Mahindra Motors announces plans to reintroduce its storied Land Rover brand to the U.S. market after a 10-year absence. The newest Land Rover, code-named Raj Sport, is rumored to be based off Mahindra's popular Ganesh midsize sport-wagon platform, and will be built at the company's 500,000-square-foot assembly plant in Pine Bluff, Arkansas.

* Upstart Chinese automaker Great Wall Motors unveils its first-ever fullsize pickup truck, the biomass-powered Shaolin XT, to rave reviews at the Frankfurt Auto Show. Journalists marvel at the truck's unique four-wheel-drive system. "Driven by gears and engaged by a lever," Car & Driver editor Sean P. Holman writes, "the Shaolin's revolutionary transfer-case design marks the century's biggest breakthrough in truck technology."

* In Washington, President Jenna Bush issues an executive order directing the Bureau of Land Management to begin soliciting private bids for leases of agency-managed parcels in northeastern Utah. The directive comes on the heels of a geological survey by the Army Corps of Engineers that discovers "huge and substantial" petroleum deposits throughout the Moab Rim Shelf region in Grand County, Utah. Representatives of the Sierra Club announce their intent to file suit in federal court to halt the leases pending environmental impact reports; officials from the Blue Ribbon Coalition announce plans to file an amicus brief.

* Ken Brubaker, who left Four Wheeler in 2010 to become President of Cadillac's Truck & SUV division, becomes the first automotive executive inducted into the Hip-Hop Hall of Fame at a ceremony held in the Bronx, New York.

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