|BMW 4-cylinder gasoline engine with TwinPower Turbo. Click to enlarge.|
BMW of North America is introducing the new TwinPower Turbo 4-cylinder engine (N20) to the X3 xDrive28i; the new engine replaces the outgoing inline 6-cylinder engine (N52) as the next step in BMW’s EfficientDynamics strategy. The N20 was first introduced in Z4, 528i, and all-new 328i. (Earlier post.)
BMW estimates that the BMW X3 xDrive28i will provide much improved fuel economy figures with the new TwinPower Turbo 4-cylinder engine over the former 6-cylinder engine it replaces—as it has with other BMW models that have transitioned from 6- to 4-cylinder engines. With the anticipated fuel economy ratings at the end of the EPA test cycle, BMW projects that the X3 will be the most fuel-efficient gasoline powered BMW SAV (Sport Activity Vehicle) sold in the US to date.
The upgrade in power and efficiency is chiefly down to the use of BMW TwinPower Turbo technology, which combines High Precision Direct Fuel Injection, Double-VANOS (VAriable NOckenwellenSteuerung) variable camshaft timing and VALVETRONIC variable valve timing along with twin-scroll turbocharging. These features give the BMW X3 power not expected from a naturally aspirated engine which would require more cylinders and larger displacement. At the same time, with its all-aluminum crankcase, this engine is lighter and more compact than a 6-cylinder engine of equivalent power.
The new 4-cylinder engine is modeled on the current multi-award-winning inline 6-cylinder engine with BMW TwinPower Turbo technology (N55).
The new BMW TwinPower Turbo 4-cylinder’s displacement of 1,997 cc delivers maximum power of 240 hp / (180 kW) at 5,000 rpm while thanks to twin-scroll turbocharging, the maximum torque of 353 N·m (260 lb-ft) is developed at just 1,250 rpm and remains constant up to 4,800 rpm. The BMW X3 xDrive28i accelerates from 0 to 60 mph in 6.5 seconds (preliminary), on its way to an electronically governed top speed of 130 mph.
The new 4-cylinder engines feature twin-scroll turbocharging. The exhaust stream from cylinders 1 and 4, and the exhaust stream from cylinders 2 and 3, follow separate spiral-shaped paths to the turbine wheel. This reduces exhaust back-pressure at low engine rpm, allowing the energy of the exhaust gas pulses to be utilized as efficiently as possible.
The combination of a high power output and a simultaneous reduction in emissions is achieved by VALVETRONIC variable valve timing and Double-VANOS variable camshaft timing. The latest generation of the VALVETRONIC system features a faster-acting, optimized stepper motor with integrated sensor. Seamlessly variable control of intake valve lift dispenses with the need for a throttle butterfly. Instead, the air mass is controlled inside the engine, resulting in faster response. At the same time, pumping losses have been reduced to a minimum.
The High Precision Direct Injection system is centrally positioned between the valves, with solenoid injectors precisely controlling the supply of fuel. The fuel is injected very close to the spark plug, with a maximum injection pressure of 200 bar (2900 psi), resulting in clean and homogeneous combustion. The cooling effect of the directly injected fuel also results in higher compression than on port injection engines, bringing further efficiency improvements.
The performance of the new engine is also due to various innovative features of the core. For example, twin balancer shafts positioned at different heights result in optimized vibration absorption, while a centrifugal pendulum absorber integrated in the dual-mass flywheel conveys a reduction in irregular running at low engine rpm.
Auto Start/Stop will now be standard on both the X3 xDrive28i and X3 xDrive35i. Under certain driving conditions, Auto Start/Stop turns off the engine when the vehicle comes to a stop, providing up to a 3% improvement in fuel economy. Once the driver’s foot is removed from the brake or the steering wheel is slightly turned, the engine will re-start automatically. This feature can be switched on/off via a button located next to the Start/Stop button.
Driving Dynamics Control with ECO PRO can be accessed by a button on the center console enabling the driver to select a new “ECO PRO” mode. ECO PRO enhances fuel efficiency by:
Optimizing drive train, heating, air conditioning and electrical functions by dialing those functions back.
Displaying driving tips on the iDrive screen to help conserve fuel.
Displaying fuel saved as “bonus” miles added to the vehicle’s normal driving range.
A new Driver Assistance Package includes Lane Departure Warning that warns the driver if unintentionally straying out of their lane.
All BMW X3s are produced in an expansion of BMW’s plant in Spartanburg, South Carolina. Technical specifications and EPA mileage ratings for the 2013 BMW X3 Sport Activity Vehicles will be announced closer to the on-sale date.