Tony Swan, executive editor of Car and Driver received the 2004
Ken Purdy Award for the following article, reprinted with the magazine’s
permission, from the November 2003 edition. The 24 Hours of Dudenhofen A sparkless push for economical speed records with a unique finish.
April 3, 2004
Do you recall your whereabouts at 10:00 Greenwich mean time on July 27, 2003? I’m not likely to forget mine anytime soon. I was pushing a one-of-a-kind Opel Speedster the last few meters into the pits at the Dudenhofen Test Center, Opel’s high-banked development track, named for the nearby town, not far from Frankfurt. This would be the kind of pushing you do with your feet on the pavement and your hands exerting pressure against the car. Not the preferred kind, entailing pedal to the metal.
It was hot and humid, and I was wearing soggy Nomex. And the car, though light in weight, wasn’t getting any lighter, nor were the Bridgestone low-rolling-resistance tires offering any less resistance to rolling. Beyond that, gullwing doors don’t make pushing any easier, since the pusher has to crouch beneath the door while conducting his battle with friction—assuming he also wishes to steer. I tried centering the steering wheel and pushing from behind, which was a lot easier, but the car stubbornly refused to maintain course, yawing gently left or right despite my increasingly colorful verbal urgings.
I was doing this because the car had ceased to function normally as I passed the pits at the outset of the 24th hour of a 24-hour run. As I trudged along, it occurred to me that during this little blip in the space-time continuum my existence was unique. Not another soul on the planet was engaged in an identical activity.
This was an epiphany with a pretty sour center. As with any other endurance driving event, the guy who’s at the wheel when the car ceases to be self-propelled loses face with the support crew. His status goes from grudgingly accepted necessity—hey, someone’s gotta pedal the thing, Jürgen—to known saboteur. Typhoid Mary wearing a name badge and warning labels would get a warmer reception. Never mind that the driving discipline was simple in the extreme: get in the car, stand on the gas—stand on the diesel, in this case—for about two-and-a-half hours, then come in for a driver change. Never mind that internal combustion ceased with no warning whatsoever, even though the crew was equipped with telemetric monitoring equipment. Never mind that I’d put up the fastest lap of the first 12 hours. Pushing the dead car into the pits and shrugging your shoulders when they ask what happened is analogous to taking Halle Berry on a date during which she’s abducted by space aliens. You’re innocent, but try selling that. Yeah, right.
On the whole, at that point it’s fair to say I would have preferred to be somewhere else—visiting the Lawrence Welk homestead in North Dakota, for example. But I was discounting the ingenuity of the Opel crew. We weren’t through yet. Nein.
But perhaps we should begin at the beginning, which dates back three-plus decades. In June 1972, an Opel GT turbo-diesel staged an endurance run on this same circuit and established a fistful of speed records for its class—diesel cars between 2.0 and 3.0 liters. The effort, made with a bubble-canopied single-seat version of the GT coupe, was the prelude to the launch of the company’s first diesel-powered car, the Opel Rekord 2.1 D.
Since then, Opel, Volkswagen, and others have made a number of diesel-powered assaults on the FIA record books, and with a new family of common-rail diesels coming onstream, Opel product planners figured a batch of new records would boost the image of sparkless ignition from the mundane realm of economic necessity to the happier precincts of fun-to-drive. This time around, they took aim at the 1.1-to-1.5-liter diesel class.
High performance was a priority, but the planners didn’t lose sight of economy. The new engine enhances the thrift tradition with cleaner combustion than previous diesels, owing to common-rail and direct-injection technology. Consequently, the car became, officially, the Opel Eco-Speedster. It was quiet, too, with little hint of classic diesel clatter. With the rear bodywork in place, the little engine was all but indistinguishable from any other small-displacement four idling at a stoplight.
The engine in question—officially, the 1.3 CDTI Ecotec—was small, indeed. Tabbed as a 1.3-liter, its displacement is actually 1248cc, and Opel calls it the smallest passenger-car diesel going. Developed at the Fiat-GM Powertrain facility near Turin, Italy, the new engine is a long-stroke design (69.6mm by 82.0mm bore and stroke), with an aluminum head and cast iron block. Its dimensions are compact, though it’s far from light—about 275 pounds, according to Hans H. Demant, who should know, since he’s “the Man” in Opel powertrain development (and GM Europe’s V-P of engineering).
The 1.3 has four valves per cylinder operated by twin cams and roller rocker arms. Fuel finds its way into the combustion chamber via a five-hole nozzle spraying at varying angles to charge the farthest reaches of the space to optimize the explosion and thus quell the sooty particulates that have hitherto helped give diesels a bad name. A turbocharger increases the volume of air available to support combustion.
The foregoing applies to the production version of the engine, which is rated at 69 horsepower at 4000 rpm and 125 pound-feet of torque from 1750 to 2500 rpm. Installed in a car such as the little Opel Corsa, it has a European-cycle fuel-economy rating of 4.5 liters per 100 kilometers, which works out to 52.3 mpg, with a top speed capability of 165 kilometers per hour (102.5 mph).
That’s pretty good, but the objectives for the record-run version of the engine were considerably more ambitious. Opel wanted the car to be capable of 2.5 liters per 100 klicks—94 mpg—and 250 km/h (155 mph).
So how do you get to that higher velocity? More power, perhaps? Hey, how do you say “duh” in German?
Opel enhanced pressure in the common-rail fuel system from the stock level—1400 bar (20,319 psi)—to 1600 (23,222), dropped the compression ratio from 18:1 to 16:1, installed six-hole injectors, added an air-to-water intercooler, and bolted on a 3K-Warner variable-turbine turbocharger with max boost of 1.4 bar (20.3 psi). That’s a bunch of boost, enough to produce instant meltdown in a gasoline engine. But things are different in diesels, since detonation is a nonissue.
The sum of the foregoing was a nice uptick in output, to a little more than 110 horsepower from 4000 to 4500 rpm, which is just about as fast as diesels want to turn. With that much boost, the engineering team could have tuned for a torque peak of 177 pound-feet but elected to hold it to 148 to avoid overstressing the lightweight automated-manual transmission chosen for the job.
This was a modified version of Opel’s five-speed F17 Easytronic, using revised internal gearing and fitted with shift buttons on the steering-wheel spokes. Besides allowing high top speeds, the transmission’s shift programming was worked out to support the ambitious fuel-economy goal, which was the other half of the project mantra—”250 x 2.5,” meaning 250 kilometers per hour top speed, and 2.5 liters per 100 kilometers. Thus the high-speed record run was augmented by a simultaneous fuel-economy competition—the Eco Challenge—on public roads among the auto scribes on hand to cover the event.
Power was only half the battle, of course. Getting a 110-hp engine to propel a car to speeds of 150-plus mph requires a car that’s more willing to be propelled than most. Under the baton of Stefan Arndt, Opel’s smoothers and shapers sat down at their keyboards and created a revised look for the mid-engined Speedster—longer, lower, slicker. The computer-generated coupe was the basis for a one-fifth-scale model that went to the wind tunnel for fine tuning. According to Opel design chief Martin Smith, there was “a fair amount” of this, some 70 hours, including final refinements on a full-scale prototype.
At 37.4 inches, the roofline of the Eco-Speedster is 6.6 inches lower than the soft ceiling of the roadster. Part of this reduction came from lowering the roof, dictating a much steeper windshield angle as well as the gullwing doors. The rest of the height reduction was achieved by dropping the static ground clearance from 5.5 to 3.9 inches. Reducing the car’s height decreased its frontal area by 12.5 percent. At the back, meanwhile, the tail was stretched by 7.2 inches to enhance airflow, and flat wheel covers were installed. The aerodynamicists also added underbody diffusers to neutralize lift at high speed and a pair of NACA ducts to augment engine-bay cooling.
The long-tail Speedster emerged with a Cd of 0.20 versus 0.38 for the production roadster, and this, in concert with the reduced frontal area, added up to a 54-percent reduction in drag, according to Opel.
Weight was obviously another key element in the equation. Although the standard Speedster’s aluminum chassis was the starting point, the body shell was fabricated entirely from carbon fiber. The engine, the transmission, the suspension components, the brakes, and the wheels were weight-optimized as well. The only Opel Speedster we’ve tested (March 2002) weighed 1980 pounds. According to Opel, the Eco-Speedster scaled in at just 1455 pounds.
Bridgestone Potenza RE040 tires designed specifically for this run were the final touch. Bridgestone cooked up three different compounds to accommodate weather variations, all with low rolling resistance as a common denominator. The plan was to use 175/55R-17s in front and 215/45R-17s at the rear, and to make one tire change about halfway through the run.
Preliminary testing indicated the Eco-Speedster was capable of performing as advertised, and the development team pronounced the effort ready to go. A date was set, the automotive press was notified, and a crack team of drivers was invited to help out with the 24-hour run. This proved to be a diverse group, including Alain Uyttenhoven, executive director of the Opel brand and an Opel board member; the aforementioned Hans Demant; Karl Mauer, Opel’s director of technical communications and a veteran of 15 Nürburgring 24-hour races; former German Touring Car hotshoe Klaus Niedzwiedz; scribes from a trio of European magazines; and your humble narrator, the only Yank.
The engine was fresh, with only 800 klicks on the clock prior to the Dudenhofen weekend; all systems had been checked and rechecked; the car was supremely easy to manage at high speeds; and the weather, though damp, didn’t seem overly threatening. What could possibly go wrong?
As you’ve already surmised, plenty. And not just in the waning minutes.
Although the official start was delayed while the FIA crew replaced a piece of timing equipment that was kicked over in the prestart photo frenzy, things began well enough at 10 past noon, Niedzwiedz pedaling the Speedster around the high banks with laps in the 156-mph range. As the small flock of reporters and guests settled into the hospitality area—nothing like a little fried calamari while watching a high-speed run—the Speedster whistled past every 1:09, and the records began to topple.
From a standing start, Niedzwiedz covered 10 kilometers at an average speed of 137.072 mph, almost 13 mph better than the mark established by a VW Golf diesel in 1993. At 10 miles, the average had climbed to 144.747 mph versus 127.831 for the VW. At one hour, the Eco-Speedster was averaging 155.279 mph, breaking the 102.615-mph mark set by an Opel Corsa turbo-diesel in 1988.
Niedzwiedz pressed on just past the 500-kilometer (311 mile) mark, boosting his average speed up to 155.878 mph for that distance, almost 54 mph better than the ’88 Corsa, and then handed it over to Uyttenhoven.
With two hours elapsed, the pace was beyond expectations. But you would never have guessed this by scanning the faces of the support crew, which were adorned with the kind of expression we usually associate with impending visits by property-tax assessors. The worry lines were so uniform they seemed to be part of the dress code, and optimism seemed suddenly to be distinctly out of place.
Assuming a suitably grave demeanor, I asked what, if anything, was amiss and why the crew had removed the car’s rear bodywork during its recent stop.
“The transmission oil,” said Mauer. “The temperatures seem to be running a little high.”
“How high is high?” I asked.
“About 155 degrees,” he said. “Normal is about 130.”
Mauer was speaking Celsius, of course. In Fahrenheit, 130 equals 266, and 155 equals 311, which is hot, even for the Mobil 1 synthetic churning around in there. Mauer added that the crew was thinking—hoping?—the problem was faulty data.
Meanwhile, Uyttenhoven was having other problems. The rain morphed from misty to torrential. Although the 39-degree Dudenhofen banking shed water like a church steeple, the surface became a little treacherous nevertheless, complicated by episodes of near-zero visibility. Uyttenhoven prudently throttled back some 15 mph until the downpour slackened, but when he began to pick up the pace, the pit crew radioed orders to hold it to about 150 mph. The transmission-oil temp was still climbing, heading toward almost 350 degrees.
When Uyttenhoven made his pit stop, the crew got the rear bodywork off again, and it was clear to anyone with functioning olfactory senses that there was nothing wrong with the telemetry. The oil had the mephitic fragrance of a Jacuzzi in Hell.
The next driver, Italian journalist Piero Vivarelli, ran at a more conservative pace—between 145 and 150 mph—while the crew figured out how to get the oil temp down to acceptable levels. When Vivarelli made his stop, just before 7 p.m., they were ready. The used-up oil was pumped out and replaced with fresh, the 215/45-17 rear tires were replaced with skinnier 175/55s, and the flat wheel covers were omitted, both tactics aimed at getting more cool air over the transmission.
The stop took almost 13 minutes, but it paid off. Bernd Ostmann, from Auto Motor und Sport magazine, climbed in and ran his entire stint at speeds of 154 to 155 mph, with the transmission-oil temp steady at about 260 degrees.
Then it was my turn—my first turn. Ostmann was hoisted out, I slithered into the cramped cockpit, the gullwing door whacked down on the top of my helmet, and I was outta there.
Like most tracks after sundown, Dudenhofen at night is a far different place from Dudenhofen by day. It’s well lit, with orange-hued mercury vapor lights poking up above the upper guard rail every few yards, but the net effect of the lighting is pure Twilight Zone. My brain knew the track to be a circular bowl, one continuous right-hand turn (running clockwise), just three miles per lap. My eyes, however, told me I was in some sort of outer-space worm hole, with the path curving endlessly up and to the right.
With the otherworldly lighting and a surface mottled by patches of moisture, maintaining a consistent line was tricky, and maintaining concentration trickier still. I began assigning myself tasks—checking off the markers posted at half-kilometer intervals around the ring, changing feet on the throttle from time to time without losing speed, checking my speed on the big LCD readout just past the pits.
After a while, this last activity became a little obsessive. The Eco-Speedster was extremely sensitive to steering input and track position. Although the going-in theory was that running a high line on the banking added distance to each lap, the car seemed happier higher than otherwise. I allowed it to creep up the banking and was rewarded by speed readouts that crept up in proportion—156 mph, 156.5, 157, 157.5—culminating in a best of 158.481.
The only hiccup in my run occurred at the end, when I came down off the banking a little too hot for cold brakes and realized I wasn’t going to be able to negotiate the serpentine pit entrance. I picked up the throttle and went around again.
No problem—at least not just then. However, Chris Harris, the British writer following me in the rotation who had witnessed the whole episode via radio communications, managed to duplicate my error, then compounded it by trying to wrestle the car into the pits anyway. He was rewarded with a spin, and the car whacked the hefty pit-lane marker lights, rearranging some of the carbon fiber.
Aside from a driver with diminished popularity, the consequences didn’t seem too severe—some five minutes’ work with duct tape, and the next driver, Karl Mauer, was on his way to the best stint of the entire 24 hours, running laps at 157 to 158 mph. The canny enduro vet drove with his lights off. This tactic saved enough energy to pare a couple 10ths per lap, and Mauer finished with the fastest circuit of the entire run: 159.2 mph.
But the encounter with the pit-lane marker lights created downstream mischief. Unbeknownst to anyone, the tape job began coming undone beneath the car, creating drag and vibration, problems that didn’t show up until Mauer handed off to Vivarelli early in the morning. The car began to slow, then slowed even more when Demant took the helm with about five hours to go.
The crew was mystified, chasing a variety of theories as Demant made a series of four- and five-minute visits to the pits that failed to restore velocity. The problem was finally identified by Demant himself when portions of the undertray began scraping the track. He came in again, the crew got the car up in the air using a handy forklift, and some 10 minutes of furious taping ensued.
With just three hours to go, Demant stopped again—some of the duct tape had come adrift, setting up a heavy vibration—and as repairs were made, I climbed in, prepared to take it the rest of the way, with one more short fuel stop.
You already know it didn’t play out quite that way. And now, the thrilling conclusion:
With the silent Speedster back in the pits, I watched as the crew made several attempts to get it running again. The engine turned freely, but there wasn’t the slightest hint of ignition. A lot of discussion ensued, all of it in German, and much time passed.
The situation was extremely frustrating to the crew, because despite earlier time lost in the pits—almost an hour, all told—and the 24th hour that was slipping away, the car had already gone far enough, fast enough to break the old 24-hour record. There was just one catch: To claim the record, the FIA rules required the car to cross the line at the end of the 24 hours under its own power.
But there was no power. A postrun teardown revealed that a fault in the fuel-metering computer had the injection system squirting just a hair—a micro-hair—too soon, which led to holed pistons and loss of compression. Lose compression in a compression-ignition engine, and what have you got? Silence, that’s what.
But the crew refused to be defeated. A plan emerged: Lock the transmission in first gear, hardwire the starter motor to the transmission, and limp the car across the finish line.
Feasible, but there was another catch. There was no way the car was going to travel almost five kilometers on battery power. Even with extra batteries, the starter would burn up. So, how to get the car close to the line so the driver could limp it to glory? Keeping in mind that pushing was allowed, but only by the driver?
The answer: Karl Mauer would push the car around the track, get in, buckle up, and complete the run. The crew was allowed to get him rolling, but only as far as the pit exit. He coasted about 50 yards, climbed out, and began pushing.
Now in his mid-50s, Mauer is one tough hombre. Besides motorsports, he also competes in endurance bicycle races and has run the New York City marathon twice. And he smokes: Marlboro Reds.
But tough carries you only so far on a hot day pushing a dead car. Soon a call went out for all drivers. The FIA observers were flexible on this issue. Any of us could push, but only one at a time.
The driver corps did it in relays, trading off at intervals of 100 or so yards. Then, with the small crowd chanting “Kar-ul, Kar-ul, Kar-ul,” Mauer pushed the car the last 100 yards, got in, belted up, and shut the door. There was an expectant hush, an agonizingly long pause, and finally the little car lurched past the timing lights for the last time. Wow.
The average speed for 24 hours was 139.858 mph, handily beating the existing record—78.780—established by a VW Golf diesel in 1977. In all, the Speedster set 17 records. The fastest lap was 1:08.039, 159.2 mph. The final lap, including pit time, consumed 49 minutes.
And speaking of consumption, average fuel economy for the entire run was 26.3 mpg, not exactly astounding, perhaps, but pretty good for a car lapping at speeds approaching 160 mph. Meanwhile, in the parallel Eco Challenge for maximum economy, the best average recorded was 2.54 liters for 100 kilometers—92.6 mpg—which ain’t bad, either.
So, guys. When do we run again?