日本丰田公司和德国大众公司分别开发了自己的直接喷射式汽油机，其目的都是为了既降低污染排放又提高燃油经济性。同一些直喷式柴油机一样，汽油被直接喷火燃烧室内，这样发动机在正常运转范围内提高了燃烧效率。直接喷射的困难在于要求燃烧稳定，性能优而NOX排放较少。解决上 Toyota and German Volkswagen have each developed their own direct injection gasoline engines, both designed to reduce emissions and improve fuel economy. As with some direct-injection diesels, the gasoline is injected directly into the combustion chamber, thus improving the combustion efficiency of the engine over its normal operating range. The difficulty with direct injection is that it requires stable combustion, good performance and NOX emissions. Solve the problem