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Some Electronic Throttle Control (ETC) Air Control Valves (ACV) on automotive internal combustion engines are susceptible to icing of the throttle valve. Ice formation can result in an increase in torque required to open or close the valve. Laboratory studies were conducted to improve the understanding of throttle valve icing on electronic throttle control valves with both aluminum and composite (plastic) bodies over various bore sizes (4 cylinder to 8 cylinder engines). Study results indicated that ice compression at the bore and valve gap, not ice adhesion, is the major contributor to the ETC-ACV icing phenomenon. In addition, testing of parts with various bore sizes, orientations and surface cleanliness resulted in further understanding of the icing issue.

This analysis was undertaken to improve the understanding of the throttle and fuel types, exhaust gas recirculation, and mileage that affect the thickness and location of throttle deposit formation. Some automotive internal combustion engine throttle bodies have experienced field issues causing increased torque in the opening direction or idle stability/stalls. To increase the understanding of the factors affecting throttle deposit formation, a measurement system was developed to quantify throttle deposit thickness. Furthermore, an analysis of variance was completed on throttles from known field usage to identify factors such as oil type, fuel type, EGR, throttle type that affect deposit thickness. Through an analysis of field vehicles with known history and throttle deposits this initial analysis identifies the key factors affecting throttle deposit build up.

The performance and exhaust emissions of a commercially available, propane fueled, air cooled engine with Electronic Fuel Injection (EFI) were investigated by varying relative Air to Fuel Ratio (λ), ignition timing, and Compression Ratio (CR). Varying λ and ignition timing was accomplished by modifying the EFI system using TechniCAL Industries’ engine development software. The CR was varied through using pistons with different bowl sizes. Strong relationships were recorded between λ and ignition timing and the resulting effect these parameters have on engine performance and emissions. Lean operation (λ > 1) has the potential to significantly reduce NOx production (110 g/kW-hr down to 5 g/kW-hr). Unfortunately, it also reduces engine torque by up to an order of magnitude (31 Nm down to 3 Nm).