Mercedes-Benz has set a new record for diesels in the legendary Pikes Peak hill-climb race with a near-production C 250 d 4MATIC. Test driver Uwe Nittel completed the 12.4-mile-long route, which includes more than 150 bends at a range in altitude of nearly 5,000 feet, in just 11 minutes 22 seconds.
"With extensive simulations and gruelling durability trials at test sites all over the world, the Mercedes-Benz testing program is one of the most rigorous in the industry," says Prof. Dr. Thomas Weber, member of the board of management of Daimler AG, responsible for group research and Mercedes-Benz Cars development. "Pikes Peak raises the bar even further, and the virtually series-production C 250 d 4MATIC proved that sporty performance and clean exhaust technology are not mutually exclusive."
The test drive at Pikes Peak also demonstrated how well Mercedes-Benz diesel powertrains are adapted to the special requirements of the U.S. market, which include extreme climatic conditions. The course’s numerous switchbacks put the car’s suspension and 4MATIC powertrain through their paces when accelerating out of bends. Meanwhile, the diesel engine had to contend with thin mountain air, propelling the C-Class to a finish line more than 14,000 feet above sea level.
"Shoving a series-production diesel sedan with an automatic transmission up Pikes Peak sounds like a crazy idea, but it was a lot of fun," Nittel reports. "It shows that the preconceived notions about diesel engines are no longer relevant."
Nittel’s extensive rallying background includes numerous victories in national championships. He was named a vice world champion in the 1996 Rally World Championship, and in 2011 belonged to the team that won the FIA European Truck Racing Championship.
Road warrior: The C 250 d 4MATIC
The 201 hp C 250 d 4MATIC, equipped with a 7G-TRONIC PLUS automatic transmission, competed in the hill-climb race in largely series-production configuration. Modifications included disassembly of the interior (typical for racing cars) as well as regulation safety modifications, including a rollover cage, racing tank, fire extinguishing system, enhanced brakes and ultra-high-performance (UHP) tires.
The diesel’s environmentally-friendly engine technology went unchanged. Thanks to a highly effective emission control system, the C 250 d is the first diesel model to surpass U.S. ULEV 70 emissions requirements, which are among the strictest in the world. With a combined rating of 34 mpg, the C 250 d’s fuel economy surpasses that of most hybrid vehicles on the U.S. market.
Diesel engine technology: clean and economical
The C 250 d is powered by a four-cylinder diesel engine with fourth-generation common-rail direct injection featuring piezo injectors, two-stage turbocharging and exhaust gas recirculation. A highly sensitive engine control system responds precisely to the most diverse operating conditions, optimizing the combustion process. The emission control system incorporates a close-coupled, electrically heated oxidation catalytic converter and a diesel particulate filter, shortening regeneration times.
The core of the emission control system takes the form of a selective catalytic reduction (SCR) catalytic converter, with an AdBlue® injector connected upstream. AdBlue is a synthetic, aqueous urea solution which causes the nitrogen oxides (NOx) to be reduced to harmless nitrogen in the SCR catalytic converters. Monitoring and diagnosis of the complex exhaust gas aftertreatment processes are performed by various sensors, including a differential pressure sensor, a lambda sensor and NOx and temperature sensors.
The hill-climb race: legendary and gruelling
With 156 bends and a nearly 5,000-foot range in altitude over a distance of just over 12 miles, the "Broadmoor Pikes Peak International Hill Climb" (PPIHC) in the US state of Colorado is arguably the most spectacular and demanding hill-climb race in the world. The uphill gradient averages 7 percent. The epithet "Race to the clouds" derives from the Rocky Mountains topography: The race begins at an altitude of 9,390 feet above sea level and concludes at the mountain’s summit 14,111 feet above sea level. The entire route has been asphalted since 2011.
PPIHC is one of the oldest motorsport events. Automobile and motorcycle races have been held at Pikes Peak since 1916, and this year’s event marked PPIHC’s 93rd anniversary. The best-known winners include Bobby Unser, who won the hill-climb race 13 times; Indycar drivers Mario Andretti (1969) and Rick Mears (1976); and rally drivers Michèle Mouton (1984, 1985), Walter Röhrl (1987), Ari Vatanen (1988) and Sebastien Loeb (2013).