SI Engine Warm-Up: Water and Lubricating Oil Temperature Influences

A Ford Valencia engine was tested with a sudden start-up to a fixed speed and load and the coolant, lubricating oil and exhaust emissions were monitored as a function of time. Steady state tests were carried out with and without air preheat and with synthetic lubricating oil. These showed that the air preheat had a major impact on the hydrocarbon emissions and this had to be eliminated if the influence of the lubricating oil and water warm-up alone was to be investigated. The synthetic lubricating oil tests showed the importance of the lubricating oil in the hydrocarbon emissions as well as the reduced sfc. Tests with water and lubricating oil initially at ambient temperatures were compared with tests with the water externally heated and the lubricating oil cold, and with cold water and hot lubricating oil. The results showed that there was still a significant transient development of the emissions when the cooling water was hot prior to the start up, but that when the lubricating oil was hot there was little transient change in the UHC emissions. The three comparative results demonstrated that the slow warm up of the lubricating oil determined the time taken to achieve the minimum sfc and dominated the UHC emissions reduction time.