BMW 3 Series Refresh Brings New 3.0L Diesel, Optional Euro 6 Compliance

12 July 2008

BMW 6-cylinder diesel engine with aluminum crankcase and 1,800 bar piezo-injection. Click to enlarge.

With its refresh of the 3 Series, BMW has introduced a newly developed in-line 6-cylinder diesel. The engine of the new BMW 330d delivers an output of 180 kW (245 bhp), 10 kW more than its predecessor, and a 7% reduction in fuel consumption. Maximum torque of 520 Nm (384 lb-ft) is available from 1,750 to 3,000 rpm.

The 330d also offers the option of BMW BluePerformance technology—with no impact on output and fuel consumption—to meet the Euro 6 emissions requirements which will not come into force until 2014.

The new BMW 330d accelerates from 0 to 100 kph (62 mph) in 6.1 seconds, and its maximum speed is electronically limited to 250 kph (155 mph). In the EU test cycle, the new BMW 330d has an average fuel consumption of 5.7 liters per 100 kilometers (41 mpg US) with CO₂ emissions of 152 g/km.

The optimized output and fuel consumption levels result from a fundamental reworking of the 6-cylinder engine in its overall design, in many of its individual components and in the arrangement of its auxiliary units compared to its predecessor 3.0-liter unit.

While the capacity of 2,993 cc has been maintained, the engine features a newly developed crankcase made of a high-strength aluminum-silicon alloy. Newly sized crankshaft bearings and big end bearings reduce frictional losses while at the same time increasing both output and torque. The crankshaft has been given even greater rigidity in the interests of higher output.

The combustion chambers have been redesigned and the height of the cylinder head reduced. The vertical arrangement of the valves together with a newly regulated air intake supports cleaner combustion with a low level of emissions out. BMW is using ceramic spark plugs—a first in a 6-cylinder-diesel engine—to improve starting properties as well as fuel consumption and exhaust emission levels during the warm-up phase.

With a weight of 185 kg (408 lbs), the new 6-cylinder diesel weighs five kilograms less than its predecessor. With its compact design, low height, a new cylinder head cover, an intake silencer which can be deformed in height and the shift of the chain drive to the back of the engine, the new diesel also contributes to the fulfilment of future requirements in relation to pedestrian protection.

With a similar geometry to that of the 4-cylinder diesel, the auxiliary units of the generator, power steering pump and air conditioning compressor are placed at the left-hand side of the engine. Since all auxiliary units are driven by a single belt, no second belt level is required. This also further enhances the efficiency of the engine since it avoids frictional losses.

The third-generation common rail injection system was specially developed for the new 6-cylinder and features centrally located piezo injectors now operating at a maximum pressure of 1,800 bar. The high-pressure pump, the feed and injection lines of the rail pressure sensor and the pressure regulation valve have also been renewed as compared to the previous version of the system.

The new engine management system has increased computing power and larger memory capacity. Among other things, this enables it to tackle the control tasks required to fulfil the EU 6 exhaust gas norm. The engine management system draws its data from sensors in the engine block, the cylinder head, the cooling system and the injection system, the oil circulation system, the exhaust manifold, the air intake system, the exhaust gas recycling system and the area of the exhaust system.

A new variable geometry turbocharger can be controlled with greater precision in relation to load and output requirements. This ensures a spontaneous response at low engine speeds as well as a high level of power density under full throttle. Modified compressor and turbine wheels give the turbocharging process enhanced thermodynamic properties.

The newly conceived exhaust gas recycling system includes a duct integrated in the cylinder head, a newly arranged feed line to the air intake system and an especially effective cooling system. The performance-optimized high-quality steel radiator is positioned at the front of the engine and fitted with a bypass shutter which limits pollutant emissions during the warm-up phase. The quantity and temperature of exhaust gas admixture can be determined precisely according to the engine operating point and engine temperature. This further reduces engine out emissions.

Additional temperature reduction is brought about by ducts in the cylinder head. The cooling effect thereby created additionally reinforces the reduction of the combustion temperature in the combustion chambers which in turn reduces the proportion of NO_x.

As standard, the new BMW 330d is fitted with a diesel particulate filter and an oxidation catalytic converter housed in a shared casing which is located immediately behind the engine. The diesel particulate filter operates maintenance-free and without the use of additives. Regeneration phases are required at regular intervals and are triggered by means of post-injection activated by the engine management system.

With its enhancements, the standard new 3.0L diesel undercuts the threshold levels set for Euro 5 emissions. The BluePerformance option integrates a NO_x storage catalytic converter into the aftertreatment system. The coating of the NO_x storage catalytic converter consists of platinum, palladium and rhodium. The catalysis produced by these precious metals causes the nitrogen monoxide and nitrogen dioxide to bond with the barium carbonate elements installed in the catalytic converter, enabling these substances to be stored in the form of barium nitrate.

By running the engine on a higher proportion of fuel for short periods of time—activated by post-injection—these nitrates can be completely combusted. The sulfur oxides caused by the combustion of diesel fuel are eliminated in the same way. In the optional configuration with BluePerformance technology, the new BMW 330d meets the future Euro 6 ratings.

The Euro 5 NO_x requirement is 0.18 g/km; the Euro 6 NO_x requirement is 0.08 g/km. The current US EPA Tier 2 Bin 5/CA LEV II NO_x requirement is 0.044 g/km (0.07 g/mi).

BMW also enhanced the four-cylinder diesels in the 320d and 318d to meet Euro 5 standards. Optimized EGR uses a high-pressure cooling unit to provide effective temperature reduction and an electrically controlled valve precisely measures the exhaust gas recycling process. The control data is acquired by means of a temperature and exhaust gas pressure sensor.

The effectiveness of exhaust gas aftertreatment has been further enhanced. New precious metal coatings for the diesel particulate filter and the oxidation catalytic converter enable even more intensive conversion or storage of hydrocarbons, carbon monoxide, nitrogen oxides and diesel particles.

All the 3 Series models, gasoline and diesel, are fitted with Brake Energy Regeneration using intelligent generator regulation. In the manual transmission version of the BMW 3 Series with 4-cylinder engines, an Auto Start/Stop Function enhances efficiency in urban traffic particularly.

Additional model-specific measures to save fuel include active control of the air intake flaps in the radiator grille to improve aerodynamics and the operation of auxiliary units—power steering, electric cooling pump, air conditioner compressor—on a needs-only basis. All versions of the new BMW 3 Series are fitted as standard with Runflat tires which have reduced rolling resistance.

Including the models BMW 320d Coupé and BMW 320d Convertible, six models of the BMW 3 Series have a CO₂ output level of 140 g/km.