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Challenges of the U.S. 500
As the chief designer ofrace-winning Mercedes-Benz racing engines in both the PPG CART World Seriesand the Formula One World Championship, Mario Illien is accustomed tochallenges. Some of the most difficult challenges Illien faces are thetechnical demands of a 500-mile Indy car race. The U.S. 500, at MichiganSpeedway in Brooklyn, Mich., July 27, is a grueling test of performance andreliability that influences the engine design process from the verybeginning.
"We always aim to have a wide powerband, a flat torque curve," saidIllien, who along with partner Paul Morgan, founded Ilmor, the raceengine-building arm of Mercedes-Benz. "That way, the engines are good forthe variable demands of road course racing and the full-throttle running ofovals. But there are some critical aspects specific to 500-mile races thatfigure into the design."
Successful Compromise
As with nearly everything in racing, engine design is a compromise. Power is a function of revolutions per minute (rpm); the higher the rpm,the faster you go. Reliability, on the other hand, can be inverselyproportional to rpm; the faster you go, the more likely something willbreak. The question Illien must answer is: How does one build a racingengine powerful enough to propel a car in excess of 230 miles per hour yetresilient enough to survive 500 miles -- more than three hours -- of nearlyconstant full-throttle running?
"There are two critical areas we look at," explained Illien, anative of Switzerland. "Valve springs are the first. Steel springs (perCART rules) are the limiting factor on rpm. In 500-mile superspeedwayraces, we run at an almost constant speed, with perhaps a 1,000-rpm range. The springs are subjected to a similar kind of stress over and over. Anykind of resonance in that rpm range could destroy the spring, the valve orboth.
"The other critical area is piston design. The pistons are exposedto a great deal of heat and mechanical stress. They must be designed towithstand those stresses and temperatures, or they can become a limitingfactor on the rpm level as well, requiring a lower Īrev limit' to make themsurvive."
Fuel Economy
The seven Mercedes-powered teams have applied strong fuel economyand strategy to good effect: six consecutive wins for Mercedes and thepoints lead in nearly every major category. Mercedes leads the enginemanufacturer's points, PPG Cup driver points (Paul Tracy) and rookie of theyear (Patrick Carpentier) standings. The U.S. 500, a race which willlikely include eight or more pit stops, presents another opportunity forthe application of such fuel economy strategy.
"Three factors affect fuel efficiency: combustion -- how fast andhow completely does the charge burn? Internal friction -- how much energyis lost in the moving of internal engine parts? And fuel preparation in theinjection system -- you're injecting huge quantities of methanol into theengine, so you want as many small droplets as possible."
Technology Transfer
Fame and fortune are the spoils of victory at the U.S. 500, but forIllien the PPG Cup crown jewel also carries a reward of a different kind:technological advancement. The saying "racing improves the breed," istrue, and never was it more so than in a 500-mile contest.
"Every new engine concept comes from experiences with previousengines," said Illien. "We're always learning from one year to the next inCART, but we've also taken a number of those ideas into our Mercedes-BenzFormula One program. In F1, you're at full throttle for 16 to 17 secondsmaximum, but in a 500-mile Indy car race, the engine must survive literallyhours of full throttle application. The lessons in reliability that wehave learned from these experiences can be applied to both programs (F1 andCART)."
If any one of the seven drivers using Mercedes-Benz power rise tothe top at the U.S. 500, scoring another win for the three-pointed star, itwill certainly be a victory by design. In 1997, Mercedes-Benz engines havepowered cars to race wins in the PPG CART World Series, Formula One and FIAGT championships (with the new Mercedes-Benz CLK-GTR). Mercedes is the onlymanufacturer to win in each of those categories this season, continuing along tradition of motorsport success and innovation. Mercedes-Benz engineshave been winning races around the globe for more than 100 years.
Ilmor Engineering: A Decade of 500-Mile Race Wins
Since 1987, Mario Illien-designed engines have won 14 grueling Indycar 500-mile races. In the same decade, no other CART engine maker has wonhalf as many.
Drivers with 500-mile race wins powered by Mario Illien-designedengines:
| Driver | Wins |
| Rick Mears | 4 |
| Al Unser Jr. | 3 |
| Emerson Fittipaldi | 2 |
| Danny Sullivan | 2 |
| Michael Andretti | 1 |
| Scott Goodyear | 1 |
| Arie Luyendyk | 1 |
| Total 500-mile wins: | 14 |
Source: Mercedes-benz USA