Sunday, September 13, 2009

Contentious Vehicle Electronic Systems

A friend in San Diego recently sent me a news story about an off-duty CHP officer who, with his wife, daughter and a relative, was killed when his 2009-model loaner crashed at very high speed.

Although the final report isn't yet in, it appears the driver had applied heavy, prolonged braking for miles prior to the impact. Witnesses reported seeing flames coming from all four wheelwells. Investigators said they were looking into the possibility that the car was equipped with dealer-installed floormats, the subject of an earlier recall after reports that they could jam the pedal and cause the throttle to stick wide open.

Investigators also mentioned that this model's engine can't be shut off unless the start button is depressed for at least three seconds. They were unsure if the driver had tried to kill the engine or shift into neutral.

It's been my experience that not every vehicle allows its transmission to be shifted from drive into neutral once underway. Some allow the selector to move but refuse to disengage the forward gear. Others—many current-model Dodges and Chryslers, for instance—allow the driver to grab neutral from drive, but limit revs to protect the engine. At the opposite end of the spectrum is the Mini, which will let drivers destroy the engine if they insist. It all depends upon the manufacturer's design philosophy.

This led me to think of some instances where I've found myself at odds with the design of a vehicle's electronic systems. (Some of my other opinions on related subjects are to be found in the road test section on

Turn Signals

I sometimes want a turn signal to flash once. Not two or three times, just once. But Audi, Mercedes, VW and a host of others know better. Depress the lever momentarily and you get... three flashes. It’s their way of saying, “No, you don’t want one flash. Nobody wants one flash. You’re changing lanes while juggling a Big Mac, placing a call on hold and checking in your mirror for a five o’clock shadow. So we’re going to flash the turn signal three times to help you out.”

Anti-lock brakes

Once I was driving a new German compact sedan in wintertime Denver. (No model names; we're talking about a difference of opinion here, not liability.) After a light snow overnight, sand trucks had been out and I could see diamond-like granules of rock salt glittering in the intersections. At their approaches, snow had been compacted and burnished into ice by the spinning tires of morning rush hour traffic.

Following another car as it slowed for a four-way stop sign, I moved off-line to avoid the icy tracks and began braking. It was instantly apparent that I'd overestimated the traction coefficient. As the back of the other car grew ominously close, I stood on the brakes and felt the anti-lock system begin pulsing. The ABS performed perfectly and not a wheel was locking—but neither was the car slowing very much. Moments away from impact, in desperation I yanked the emergency brake lever and locked the rears. There was a series of shudders as the rear tires chewed down toward the pavement, building up little piles of debris ahead of themselves. I lurched to a stop with millimeters to spare.

Moral: anti-brakes are generally wonderful, but not in every situation.

Electronic Stability Control Systems, Part One

At a press event a few years ago at Willow Springs Raceway north of Los Angeles, I was the first journalist of the day to drive a new German performance sedan. Its robust 342-horsepower V-8 was a treat, but I despaired of the ESC system’s heavy-handed intrusion. No matter how smoothly I drove, just when I wanted full power to exit the off-camber, medium-speed Turn 5, the electronic nanny sensed imminent disaster and instantly chopped engine power.

On the second lap I pressed the ESC switch to shut if off, an event verified by a big amber warning light in the cluster. Freed from the hobble, at Turn Five I tried a different line, one I’d seen Hurley Haywood try earlier in a 997 C4 Porsche—and found I’d turned-in a bit early. No worries. I let the back end rotate under hard braking, applied opposite lock and, at the appropriate moment, toed deep into the throttle to straighten it out. In response, the engine dropped to idle and I could feel the ESC vainly locking the outside rear brake as I executed a snap spin, coming to rest backward with the right wheels on the marbles.

As I entered the pits, the manufacturer's West Coast PR manager was waiting silently for me by the pit wall, hands clenched behind his back. He didn’t look happy. There wasn’t much to discuss; spinning a car on a race track generally indicates driver error.

“One hundred percent my fault,” I stammered. “I thought ESC was shut off but maybe it wasn’t. I apologize for spinning your car.” He graciously accepted my apology—but the car was done for the day. Though it was unscathed, a few small pebbles had lodged between a wheel rim and tire, forcing him to withdraw the vehicle from the event.

Heading home on the plane the next day, I was scanning Car and Driver magazine. By coincidence, they’d tested the same car some weeks earlier. One of their complaints: an intrusive ESC system that couldn’t be disabled. They'd discovered that when the system indicated that it was off, it really wasn’t. Turning if off merely raised the intervention threshold a bit. The ESC systems of other manufacturers are similarly deceptive. And there's no way to know their truthfulness until the limits are probed, but then it's usually too late.

Electronic Stability Control Systems, Part Two

A big domestic manufacturer debuted electronic stability control technology on its flagship sports car and soon after its introduction, I was driving one southbound on the Sam Houston Toll Road in Houston. About ¾ mile ahead I saw that the highway zoomed upward sharply as it made a high arc to clear a dozen lanes of Interstate 10 lying far below.

I also noticed a little rain squall moving laterally across my path and estimated that I'd meet the rain very near the summit of the flyover ahead.

Presently, cruising in lane one, the farthest to the left, I hit the uphill section and began climbing. Although noontime traffic was plentiful, no vehicles lay between me and the summit, a situation for which I'd later be thankful.

Right on schedule, as the road leveled off, the advancing black rain cloud moved to intercept me. In anticipation, an instant before piercing the band of rain I reached down for the wiper switch. I was rotating the lever when the blast of water struck the windshield. Without warning, the car snapped sideways. Not a wee bit, either; I was now viewing the freeway through the passenger window.

I lifted from the gas, countered quickly with an armful of opposite lock and the car obediently straightened itself. Then it executed a snap-spin in the opposite direction. This is extremely unusual behavior for a thoroughbred sports car. Actually, it's fairly weird for any vehicle found outside an amusement park.

I'd passed the summit and now was heading downhill, still moving along briskly. A third spin was countered by yet another application of opposite lock, but I was fast running out of ideas. I was off the gas and by rights, the rear end should have hooked up. The car's steamroller Goodyear Eagle F1 Supercar tires are a closed-tread summer performance design and not as sticky as some in the wet, but there wasn't nearly enough water on the pavement to induce this kind of behavior. The effect was identical to a car whose emergency brake is yanked at high speed in mid-curve.

Meanwhile, the electronic stability control system was trying to sort things out. I could feel it locking and releasing the offside rear brake as the back end slewed sideways. This wasn't quite what I had in mind. When a rear tire is sliding, the first order of business is to get it rolling again. But the ESC had its own ideas for a solution.

When the car broke away again I was late in catching it; on the next oscillation it was gone. As I sliced across three lanes backward, heading toward the right-hand railing, there was just enough time to try hard acceleration and opposite lock. No response; dynamically, the car was in way more distress than I or any software program could handle. Finally I stood on the brakes and waited for the impact.

As the car executed an additional half-rotation clockwise, the left quarter struck the guardrail and slammed the car full-length against the concrete, where it came to rest backward.

In the silence I glanced at the cluster, now aglow with warning lights. Clutch in, I cranked the 400-horsepower engine and it caught instantly. Cars were approaching, speed undiminished, apparently unfazed by the sight of another car parked facing them in a travel lane. With no shoulder available for U-turns and with zero time, I dumped the clutch in first gear to rotate the car 180 degrees and accelerated to 50 mph, listening for damaged rotating components. I limped off at the next exit for an inspection.

Surprisingly, the composite bodywork proved far more resilient that I'd expected. It was badly cracked vertically over the left wheelwell and the left taillight area and bumper were ravaged. There were scuff marks all along the left side and both driver-side wheels were deeply scratched by the concrete, but neither was bent. And the car still drove perfectly.

That afternoon I put the car on a lift to learn the full story. I found no additional damage--and quickly discovered the reason for the treacherous handling in the rain. The 3,500-mile press vehicle had two pristine front tires with full tread depth. But the rears were worn into the wear bars, averaging barely 2/32-inch apiece. In effect, they were racing slicks.

Why was I driving a car with bald rear tires? Chalk it up to blind trust and complacence. Auto manufacturers engage press-fleet management companies to maintain these vehicles and strictly speaking, it was their problem. But neither they nor I expected to find a month-old car that required new rear tires—even a high-performance sports car. Uncharacteristically, I hadn't closely checked the condition of the tires before departing.

With the secret of the tires revealed, I pieced together the event. When the toll road changed from uphill to downhill—at almost the precise moment I entered the rain—the ESC system couldn't sense the subtle dynamic weight transfer. (This effect was heightened by a nearly-empty gas tank.) It also didn't know that the rear traction coefficient had changed in lockstep, from sticky to greasy, as the bald tires hit the water. With the throttle feathered and the car rotating around the front axle, the ESC assumed that it could help restore stability by applying rear braking. And it was wrong.

Ironically, I later drove an identical car on the West Coast and on this one, all four tires were bald. (I can't complain about their condition; the company PR manager kept the car in service solely to let me drive it. The following week it was sent to auction.) Driving at speed in a downpour on a nearly-deserted I-8 east of San Diego, it readily skittered into adjacent lanes in reaction to deep standing water. But although it had very little grip, on equally-worn tires it was at least predictable and fairly manageable.

Moral: the ESC system is a wonderful invention, so good that on most vehicles, I leave it engaged during street driving. But it can't account for every variable. Like most electronic systems it's usually a friend, but like most friends, it's not perfect.