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For future fuels it's no idle matter

With diesel engines powering more and more cars, the search to reduce one of the diesel’s least desirable characteristics – noise and vibration when idling – has come under sharp focus.

Engineers have reduced the engine idle speed to cut fuel consumption (30% of a diesel’s fuel consumption in city traffic happens when the car is stationary) with a consequent increase in idling vibration, and now fuel manufacturers are involved in addressing the problem.

But without an objective way of measuring the relationship between the physical characteristics of diesel engine idle and driver response, ranking different chemical additives according to their effect on idle noise and vibration would be impossible.

Brunel’s Professor Joseph Giacomin of the Perception Enhancement Research Group has developed such a test, working with Dr Marco Ajovalasit. At its heart is the idea of accurately measuring steering wheel vibration, a key element in a driver finding it unpleasant to sit in an idling vehicle.

The test was rapidly adopted by petrochemical giant Shell Group. All new Shell fuels now have to pass the new test standard and two commercial fuels have been modified by Shell to minimise idle roughness using the results.

Car manufacturers have also welcomed the new test standard. For them the challenge is that while all drivers want to achieve maximum miles per gallon they now expect levels of comfort and quiet undreamt of even a decade ago.

Engineers at Ford, Bentley, BMW, Fiat, Ferrari, Jaguar Land Rover, Peugeot-Citroen and Renault are all using the test standard protocol and acceptability metric to rank the success of their efforts to reduce idling diesel engine vibration.