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The drive for lower CO₂ emissions places ever greater demand on cooling dissipation for a multi-cylinder internal combustion engine. This challenge has increased the requirements of the engine cooling system, particularly in countries where high ambient temperatures prevail and HVAC usage is high. Environmental necessity coupled with market demands have resulted in cars which emit a higher level of cooling fan noise which is intrusive in an urban environment and objectionable to customers. Conventional quantification of noise using traditional units and metrics was found to be insufficient for effective Sound Quality analysis. To assist Bentley Motors, a high performance luxury vehicle manufacturer, with its brand cachet and its commitment to the environment and customer, a new sound metric analysis has been devised to help the business deliver an ever-quieter exterior power unit cooling system.

Ever increasing challenges on reducing emissions and improving fuel economy has led to the development of not only alternate fuels but also new Powertrain technologies. One such technology employed within the new Bentley Mulsanne is cylinder deactivation, where 4 out of 8 cylinders of a large displacement V8 engine are turned off during light load conditions. This paper identifies the considerations and technical development that was undertaken to deliver limousine levels of cabin refinement with imperceptible half engine mode operation under cruise conditions whilst achieving the desirable sporty character of a large V8. A practical approach to transfer path analysis incorporating structural path disconnections and exhaust orifice routing and its benefits are discussed.