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The use of two or three FID hydrocarbon analysers for the determination of condensable or liquid unburned fuel is described. Each FID has upstream pumps and filters in separate sample conditioning systems operating at three different temperatures of 180C, 50C and 2C. The 50C system could operate at any temperature up to 100C, the use of 50C was because this was the temperature used for sampling diesel particulates. The difference in the three hydrocarbon readings was used to determined on a mass basis the condensable UHC over the sample temperature difference of either 180C to 2C or 180C to 50C. The latter hydrocarbon difference was shown to be close to the particulate fuel fraction of the SOF. A range of applications of this technique to both diesel and spark ignition engines are described, including the warm-up of a Ford CVH SI engine and the influence of nozzle sac volume on condensable hydrocarbon emissions in a Perkins 4-236 diesel.

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 test procedures used to investigate the transient warm-up of two Ford 40 kW SI engines are described. Water, engine casing and lubricating oil temperatures were monitored and the rates of temperature rise determined as a function of engine speed and power. The temperature results showed that for both engines the lubricating oil was the slowest component in the warm-up and may be the limiting factor in engine warm-up. A particular emphasis has been placed on monitoring the gas composition during the warm-up. A special feature of this system is the use of two UHC FID analysers operating at 180°C and 2°C. The difference in the two UHC readings is a measure of the high molecular weight condensible UHC or unburnt liquid fuel that is emitted. It is shown that this is quite significant during the initial period of warm-up.