The interior noise samples in the assistant driver ear's position from four types of cars at different gears and velocities were selected as the evaluation objects. The subjective evaluation test of sound quality was carried out with the magnitude estimation and the paired comparison. Several primary objective psychoacoustical parameters of these samples were calculated. By way of linear correlation and the multidimensional regression analysis, an equation between the subjective evaluation level and the objective psychoacoustical parameters was gained. The research results indicate that the vehicle interior sound quality preference under the steady operation conditions is affected by two psychoacoustical parameters: loudness and sharpness.

The cold start tests were performed comparatively for the liquid petroleum gas (LPG) and gasoline engines at the ambient temperatures of 9,15 and 20 ℃ respectively. The results showed that the fuelair mixture suitable for the LPG engine start is leaner than that of the gasoline engine. The first fuel injection pulse width for the start of the gasoline engine is about 6.9 times of that at the normal idle condition, while it needs only 2.5 times for the LPG engine. Because of the lower volumetric efficiency, the initial throttle openings for the start and idling of the LPG engine are larger than those of the gasoline engine. Generally speaking, the start behavior of the LPG engine is better than that of the gasoline engine.