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Concerns over greenhouse gas emissions are driving governments and the automotive industry to seek out ways of reducing vehicle CO₂ emissions. Engine friction reduction is one means of reducing CO₂ emissions, through fuel consumption improvements. Of the different systems within the engine, the camshaft timing drive can contribute around 5 to 10% of the overall engine friction. It is therefore a system that can benefit from careful optimization. MAHLE has undertaken a motored friction-testing program on a 2.2-liter turbocharged diesel engine with the following different types of camshaft timing drive: - Chain drive with hydraulic tensioner. This is the standard configuration for this engine. - Chain drive with friction tensioner. - Wet belt drive. - Dry belt drive. Testing was conducted to allow the differences in friction between the different drive configurations to be calculated, by comparing each camshaft drive against the standard chain drive system.

Concerns over greenhouse gas emissions are driving governments and the automotive industry to seek out ways of reducing vehicle CO₂ emissions. Engine friction reduction is one means of reducing CO₂ emissions, through fuel consumption improvements. The ancillary drive system typically contributes up to 8% of the total engine friction level, so improvements in this system can make a real difference to engine efficiency, fuel consumption and CO₂ emissions. Mahle has undertaken a series of rig tests, based on a 2.5-liter gasoline engine, but built to a minimum friction level of hardware. Using motored drive torques, the losses associated with different alternator drive concepts was investigated: - Standard 150A alternator, - Reduced capacity 120A alternator, - Reduced capacity 120A alternator driven by a dual speed gearbox, and - Reduced capacity 120A alternator driven by a twin-belt dual ratio pulley.

Concerns over greenhouse gas emissions are driving governments and the automotive industry to seek out ways of reducing vehicle CO₂ emissions. Engine friction reduction is one means of reducing CO₂ emissions, through fuel consumption improvements. One area where it is felt that friction reduction is possible is in connection with the camshaft bearings. Mahle has conducted experimental evaluation of rolling element bearings used to support camshafts, replacing the standard plain journal bearings. The aim of the testing was to gain an understanding of the durability of rolling element bearings, tested in a range of different operating conditions. The controlled test conditions included variations to: - Camshaft speed, - Oil temperature, - Oil age/specification, - Oil supply method/flowrate, - Bearing journal line bore misalignment tolerance, and - Bearing journal diametrical tolerance.

Concerns over greenhouse gas emissions are driving governments and the automotive industry to seek out ways of reducing vehicle CO₂ emissions. Engine friction reduction is one means of reducing CO₂ emissions, through fuel consumption improvements. One area where it is felt that friction reduction is possible is in connection with the camshaft bearings. The use of rolling element bearings is generally considered to provide friction reductions by two means: 1. As a direct substitution of the journal bearings by rolling element bearings and 2. As an enabling opportunity to reduce the oil flow requirement of the engine. MAHLE has undertaken a motored friction-testing program on a 2.5-liter gasoline engine, comparing the drive torques associated with the standard camshaft bearings and also with camshafts supported by rolling element bearings. The test engine incorporated a direct-acting valve train design.

Evolving emissions legislation and concerns for diminishing fuel reserves continue to prompt the automotive industry to seek improvements in engine operation. The application of advanced combustion and system-based concepts is being studied in detail. However, it is believed prudent to first consider the optimization of the friction of the engine, to allow a more cost effective CO2 and fuel consumption reduction policy. MAHLE has developed an optimised friction engine to demonstrate the potential fuel consumption gains available to engine manufacturers and designers. The baseline 2.0 litre turbocharged, direct injection gasoline engine was modified to suit the application of new friction optimized components. This included piston, ring pack, connecting rod, crankshaft bearings, lubrication system, valvetrain and cooling system. A discussion of the design changes, including analysis results, is made. Motored rig and fired engine test results are presented to show the individual gains.