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2011 BMW Z4
The twin-turbo straight-six power unit already giving the 2011 BMW Z4 sDrive35i truly impressive dynamics and all-round performance is characterised in particular by its spontaneous and direct response to the gas pedal, fascinating free-revving performance, and unusually economical use of fuel for a car in this class.Now the outstanding potential of this power unit is being put to even greater use in the new version of the BMW Roadster, features such as optimised air supply and increased boost pressure ensuring an even better flow of power with the same high standard of efficiency.The combination of BMW Twin Turbo Technology and High Precision Injection offers a level of performance a naturally-aspirated power unit would only be able to provide with a larger number of cylinders and extra displacement, meaning far higher weight and significantly greater fuel consumption.Instead, the BMW Twin Turbo power unit uses two small turbochargers which, through their low inertia, cut in from the start at relatively low engine speeds, each supplying three cylinders with compressed air. As a result, power and performance are built up with a level of spontaneity quite unusual on a turbocharged engine. The turbocharger system developed for the power unit of the new 2011 BMW Z4 sDrive35is maintains a high boost pressure throughout the entire load range. Peak torque now increased to 450 Newton-metres or 332 lb-ft comes from a low 1,400 rpm and is maintained consistently all the way to 4,500 rpm. Maximum output of 250 kW/340 hp, in turn, is delivered at 5,800 rpm.
The 2011 BMW Z4 sDrive35is offers its outstanding power and performance consistently at all times. But this does not mean an increase in fuel consumption and emissions. On the contrary – averaging fuel consumption of 9.0 litres/100 kilometres (equal to 26.1 mpg US) and CO2 emissions of 210 grams per kilometre in the EU test cycle, the new top model offers the same superiority also in this respect as the BMW Z4 sDrive35i with Sport Automatic.This unusually good balance of performance and fuel consumption results from the fundamental design and layout of the six-cylinder combining BMW Twin Turbo Technology with High Precision Injection. So once again, the qualities of direct gasoline injection featured in this engine come out very clearly, piezo-injectors positioned in the cylinder head between the valves and therefore in the immediate vicinity of the spark plugs ensuring particularly precise dosage of fuel and a clean combustion process.Opening up to the outside, the injectors operate at a pressure of up to 200 bar, distributing fuel in a conical spray pattern throughout the entire combustion chamber. A further advantage of such direct fuel injection is the cooling effect allowing higher compression and making the combustion process even more efficient.
