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Because of recent strong demands for environmental protection, all nonroad engines for agricultural and construction equipment should be conformed to the exhaust emission regulations in Japan, the United States and Europe. Some regulations include transient smoke standard at free acceleration in addition to exhaust emissions at steady state condition such as nitrogen oxides (NOx), hydrocarbon (HC) and particulate matter (PM). Therefore, especially a turbo charged diesel engine needs a countermeasure to reduce the smoke level at free acceleration. This study confirms a mechanism of the smoke discharge at free acceleration and realizes that the injection pattern of the PFR injection pump with timer function reduces the smoke level at free acceleration. As a result, we could develop the engine complied with the transient smoke standard without boost compensater, with which it is very difficult for small engines to make a fine adjustment of proper fuel delivery.