The New BMW 3 Series Coupe - Twin Turbo 3 Litre Engine Performance Figures | Part Two

BMW 3 Series Coupe

Twin-turbo in-line six-cylinder

The all-new Coupé bodyshell clothes the twin-turbo 3.0-litre engine in the new BMW 335i SE that develops 306hp and 400Nm of torque between 1,300 - 5,000rpm. With such performance statistics, the 335i forms the pinnacle of the new 3 Series range.

The 335i SE Coupé accelerates from zero to 62mph in 5.5 seconds, and, if left unchecked, would travel on to an electronically-limited top speed of 155mph. This level of performance is made possible by two turbochargers, each supplying compressed air to three cylinders each. The use of two smaller units ensures that the turbochargers react more quickly to changes in the throttle position all the way to the 7,000rpm red line while also eliminating the previous scourge of turbocharged engines - ‘turbo lag’.

The turbocharged engine is also considerably lighter than a normally aspirated powerplant of equal power. In the case of the 335i, the new twin-turbo six-cylinder engine weighs approximately 70kgs less than an eight-cylinder engine of corresponding performance. This weight advantage benefits both fuel economy and weight distribution.

BMW’s all new high-precision Direct Injection system also aids these high levels of performance while also benefiting economy. Piezo injectors, located centrally in the combustion chamber between the inlet and exhaust valves, deliver atomised fuel in a conical burst into the chamber to ensure a smooth, efficient burn.

Piezo crystal injectors work when an electrical current is passed through the crystal to create a very precise and consistent fuel delivery. The result? Only the exact volume of fuel required is delivered into the combustion chamber on each cycle guaranteeing that all the vapourised mixture is burnt. This method of injection also serves to aid combustion chamber cooling, thus offering a higher compression ratio. As a consequence, the new car delivers an average fuel consumption of 29.7mpg on the combined cycle.

Entry-level six-cylinder

At the launch in September, the new 325i SE Coupé will form the entry point to the range. Delivering 218hp and 250Nm of torque from its 2.5-litre in-line six-cylinder engine, zero to 62mph is achieved in 6.9 seconds and the top speed is 153mph. However, performance does not compromise economy with the 325i SE Coupé delivering 33.6mpg on the combined cycle. This is made possible thanks to BMW’s patented VALVETRONIC variable induction technology and VANOS variable valve timing that, when combined, balance the requirements of performance and economy.

This level of economy is also made possible as a result of a number of weight and power saving measures in the engine. The 325i Coupé is the latest BMW to benefit from the magnesium-aluminium composite cylinder block first seen on the BMW 630i in spring 2004. The lightweight combination of materials reduces the overall mass of the car and helps achieve the near-perfect 50:50 front-to-rear weight distribution for improved handling.

Finally, the 2.5-litre engine uses an electrically-powered water pump. This not only eliminates the engine power normally needed to drive a conventional crankshaft driven unit but also reduces the engine heat-up time to improve engine efficiency and occupant comfort.

continues... | Part Three

Published : 22/04/06 Author : Melanie Carter

BMW 3 Series News

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