BMW’s Advanced 335d and X5 Clean Diesels Coming to American Roads

BMW will begin selling two diesels, the 335d sedan and X5 xDrive35d Sport Activity Vehicle, in all 50 states in the fall of 2008. This is the first BMW diesel for the U.S. market since the BMW 524td sold here in the 1980s. The BMW 524td was acknowledged as the fastest diesel of its time. BMW currently offers seven diesels -- three four-cylinders, three six-cylinders, and a V-8 -- in other markets. In fact, 67 percent of the BMWs now sold in Europe are diesels.

These new diesel vehicles exemplify the BMW EfficientDynamics strategy that aims at combining maximum driving pleasure with minimum fuel consumption and emissions. That adds up to more environmentally-friendly Ultimate Driving Machines. To meet this objective, the 3.0 liter in-line six-cylinder engine uses BMW Advanced Diesel technology that includes Variable Twin Turbo Technology and BluePerformance. This allows BMW meet the stringent U.S. federal Tier2/Bin 5 requirements so they can be sold everywhere in the U.S.

With Variable Twin Turbo Technology, a small turbocharger operates at low speeds. Its low inertia allows it to produce boost and provide instant response to even the smallest throttle input without turbo lag. As engine speed increases, a second, larger turbocharger kicks in, developing maximum torque of 425 lbs-ft at just 1,750 rpm. Maximum power output is 265 horsepower. An efficient, high-performance electronic engine control unit manipulates the interaction of these two turbochargers.

This engine, which was first introduced in 2007, offers other features including an aluminum crankcase in lieu of a cast iron one, previously a heavy necessity that handicapped the diesel engine, especially in high-performance and agile cars. A third-generation, common-rail direct fuel injection system is also incorporated. Its precision piezo-injectors deliver the precise dosage of fuel into the combustion chambers with the smallest volume of pre-injection. This ensures a particularly clean injection process with optimized fuel consumption, minimum emissions, and smooth, quiet running.

To fully comply with emission standards in California and other U.S. states, BMW uses selective catalytic reduction (SCR) technology to handle NOx emissions. Called BluePerformance, it incorporates an oxidation catalyst placed just downstream of the exhaust manifold, a diesel particulate filter (DPF) housed in the same unit, and an SCR catalyst incorporating urea injection. In addition to filtering out even the smallest particles from the exhaust gas, this combination ensures effective reduction of nitric oxides (NOx) by way of a chemical reaction within the exhaust system. This reaction is initiated by the injection of a small dose of urea, or "AdBlue." AdBlue is already widely used in Europe. The ammonia generated within the SCR catalyst converts nitric oxides into benign nitrogen and water vapor.

BMW uses two tanks for the AdBlue solution, a 1.6 gallon "active" tank and another 4.5 gallons in a passive tank. This is a sufficient volume of the urea solution so replenishment can be done with oil changes, both covered by the BMW Maintenance Program. Refilling of the AdBlue tanks is a no-charge service for four years or 50,000 miles. In the BMW 335d, the active and passive tanks are at the rear end of the car, while in the BMW X5 xDrive35d the active tank is in the front right section of the engine compartment, with the passive tank under-floor next to the transmission. Since the urea solution freezes at 12.2-degrees F, the active tank and dosage pipes are heated. The DPF does not require maintenance and regenerates itself by incinerating the diesel particles as necessary.

The 335d can accelerate from 0-62 mph in 6.2 seconds while offering fuel economy of 23 mpg in the city and 33 mpg on the highway. This is about 25 percent better compared to a similar displacement gasoline engine. The X5 xDrive35d can accelerates from 0-62 mph in 7.2 seconds with fuel economy of 19 mpg city and 25 mpg highway.

BMW's diesel advancements are obvious. A BMW diesel in the 2008 model year generates only one percent of the particulate emissions originally contained in the exhaust gas stream of a 1983 diesel model. This innovative technology now enables BMW diesel models to fulfill U.S. market demands in terms of power, performance, running smoothness, efficiency, and emissions limits. That signals a potentially lucrative new market for BMW diesels in the years ahead.