The effects of thermal state changes on friction during the warm up of a spark ignition engine

The extent to which thermal behaviour of a modern 2.0l, 4 cylinder spark ignition engine can be manipulated to improve fuel economy during warm-up and fully warm operation by influencing local thermal conditions has been investigated. Experimental results providing a detailed insight to variations of metal, oil and coolant temperatures are presented and described. The different relative rates of warming, particularly between locations around the combustion chamber and those at the bottom of the engine around the crankshaft and sump, give rise to significant changes in spatial temperature distributions as warm-up proceeds and final steady state values are established. The friction penalties and potential to reduce friction by modifying temperature distributions are described. The routes by which inroads might be made in this direction are explained, and practicalities and benefits considered.