by John Robison

[John Robison, Springfield, MA, services Land Rovers and other marques at his company, JE Robison Service while enjoying the success of his latest book, Look Me in the Eye –ed.]

In this article I’d like to take you inside the electronics on a Range Rover Sport. I think you’ll be amazed at how sophisticated these machines have become.

If you were to name one particular capability that Land Rover was known for, what would it be? The wise guys among you would pick oil leaks or Lucas electrics, but I’d pick surefootedness or superior traction. To me, that’s what Land Rover is all about. From the very beginning, the Land Rover was a vehicle that went where nothing else could. And even more important – it came back, under its own power.

When you think about it, the coming back part is often the hardest. After all, if a ravine is steep enough, you can get anything to roll to the bottom. Rusting Lincolns and Caddies at the bottoms of the gullies and canyons out west are certainly testament to that. But it takes an exceptional rig to reach the bottom intact and an even more exceptional rig to climb back out under its own power.

The Series Land Rover was such a rig. A well tended Series truck could climb anything, even – as we saw in The Gods Must be Crazy – trees. In the beginning, Land Rover’s off-road prowess came from its mechanical design. It had a unique blend of weight and balance, suspension travel, gearing, and four wheel drive. But the Land Rover’s design came with some built-in limitations and some of them significantly reduced on-road capability. When Land Rover returned to the American marketplace in 1987 with the Range Rover, it was clear something had to be done if they were to maintain their off-road reputation while delivering the speed, power and boulevard ride demanded by the American market.

For this generation of the Range Rover, Land Rover set its sights on the top positions on both the road and the trail. So if they had to climb trees, they had to do it automatically, while the stereo played and the air conditioner kept the passengers cool. That kind of automatic operation can only be achieved with electronics.
As a country, England is not known for it’s prowess in that field, but they pulled things off pretty well in the latest generation of Rovers.

Rover applied electronics to many aspects of vehicle management. Let’s look carefully at one area – traction control. This system began as an outgrowth of the antilock brake system (ABS) sourced from Wabco of Germany for the upscale 1990 models.

After using the ABS system alone for a few years, Rover upgraded to a fancier version that combined ABS and traction control. That system used the ABS wheel speed sensors to detect a slipping wheel that speeds up when traction was lost. The control unit then responded by applying brake pressure to a single wheel. By grabbing the slipping wheel, traction is transferred to the wheels that still had grip and the truck moved forward. At first, traction control was limited to the rear wheels, but by 1995 it was expanded to cover all four corners.

Electronic traction control essentially took the place of mechanical front and rear differential locks. For the first time, a driver could enjoy the interior amenities as the car took care of itself in mud or snow. The electronic system engaged and disengaged as needed, so there were no worries about drivers leaving diff locks engaged and breaking things. The electronics also worked smoothly, preventing the broken axles and joints that come from aggressive use of hard mechanical locks.

I was impressed by the system the first time I drove it, in a 1993 County LWB. The truck would begin to slip in mud or snow, the traction control would begin buzzing, but the Rover just kept moving forward. It was remarkable, but it took some getting used to. When the system actuated, it made a loud noise, and your instinctive reaction was to let off the gas when you heard it; actually, the best thing to do was to hold steady. Once I learned to do that, I got great results with this system. That basic traction control served Land Rover well for ten years. The only trouble was – everyone else adopted similar electronic traction control systems, so the capability that was unique among four wheel drives in 1995 was common by 2005. If Land Rover wanted to stay ahead of the pack, something more was needed. That’s what led to the Terrain Response system that debuted in the new LR3 and Sport models. Terrain Response takes electronic vehicle management to a whole new level. Check out the way a new Sport handles wheel slip and you’ll see how far Land Rover has come.

The first step remains the same – the wheel speed sensors detect a slipping wheel, and the controller applies a brake to stop the slippage. That was the end of the old system’s capability, now it’s just the beginning. As the load shifts to the other wheels, sensors monitor them, too.

If more wheels begin to slip, but the vehicle is moving, the traction control program doesn’t just apply more brakes. It does something else – it tells the engine management system to reduce power so the slipping wheels can regain traction. The computer balances brake application with throttle modulation to keep the vehicle moving with minimum slippage. That combination makes for a significant jump in the system’s effectiveness. Earlier Land Rovers used a mechanical connection between the gas pedal and the engine. Today’s Rovers use a drive-bywire system, where the gas pedal sends a signal to a throttle control unit, which signals the engine management computer, which in turn sends a signal to the electronic throttle. By going to drive-bywire,

Land Rover engineers allowed the traction control system to control power output in marginal situations.

In addition to backing off the gas to prevent wheel spin, the Terrain Response program reduces the speed at which the vehicle responds to the throttle. When the ground is slippery, everything has to be gentler to keep the wheels from spinning. A quick jab of the gas pedal will produce a snappy takeoff on pavement, but it will just dig a hole in packed snow. Terrain Response compensates for overenthusiastic drivers with very gentle acceleration in deep snow or mud. That response modulation is the first feature that sets Terrain Response apart from traction control in other brands.

If the wheels continue to slip, the Terrain Response has yet another trick up its sleeve. The new Rovers use computer controlled air suspension. Now, that system is also called upon to increase traction. They achieve that by sending more pressure to the air springs at corners that are slipping. That presses the slipping wheels more firmly into the ground and helps the vehicle maintain its footing. It’s the computerized equivalent of piling a few guys on the back bumper to give slipping wheels traction.

In addition, if the wheel is slipping because it’s in a deep rut, the system can shove the tire down several inches to find firm ground. When that happens, the computer knows to raise the whole vehicle to keep it clear of rough ground later, and it does that automatically.

As soon as the truck has good traction on level ground, all systems return to their normal modes. The whole thing is actually invisible to the driver, except for the results, which are remarkable. Last winter, I took my own Sport and my old ex-NATO ‘91 Defender into a snow covered meadow to compare traction. The Sport had stock Continental all-season tires. The Defender had Michelin XZL military tires, one of the gold standards of off roaders. The result? When it came to traction, electronics allowed the Sport to easily outperform the Defender.

I was surprised, but the results spoke for themselves. The new Sport’s traction is impressive by any standard. Of course, the Defender still has the edge with skid plates, tire chains and a winch, but that wasn’t the purpose of this particular comparison. And you could always fit those things to a Sport if you were so inclined. In fact, I’m looking forward to the day a Sport enthusiast brings one to our shop for some serious off-road customization. I think the result will be very impressive.

When the ground gets rough, the Terrain Response does even more. It modulates the throttle and the transmission to get up hills, and then it uses the brakes to automatically keep the vehicle from running away on the downgrades. It’s a little surprising the first time you experience it, as it chatters away, but there is no doubting the effectiveness of the system. All this interplay between suspension, engine, transmission, and brakes couldn’t take place without a sophisticated computer network. In a Rover, they call that network the CAN bus, short for Controller Area Network. CAN allows all the different computers in the car to share and exchange data, and it allows them so spread tasks across multiple systems. If Rover were to combine the electronic finesse of today’s Sport with the mechanical brute-force capability of the Defender, the result would be impressive indeed. The obvious question is – why don’t they do that? I believe the answer is twofold: ruggedness and serviceability.

The electronics are great when they work, but you need fragile and expensive electronic testers to service the systems. That’s a problem in much of the world. There is also the issue of training service personnel to fix the electronic systems. In addition, the simple mechanical systems Land Rover built their name on are more rugged when there’s constant exposure to off road conditions. The electronics are great, though, for anyone who off-roads occasionally.

( For more information, check out www.robisonservice.com or jerobison.blogspot.com )

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