| 摘要 |
PURPOSE: A harmful exhaust gas reducing method in case of cold start is provided to sacrifice a part of engine output to activate a catalyst in an earlier stage, thereby reducing an amount of harmful exhaust gas generated in an initial time of cold start. CONSTITUTION: A harmful exhaust gas reducing method in case of cold start includes the steps of checking whether a starting temperature of an engine is lower than a threshold value or not after preheating preparation time from the engine starting, finishing the control if the engine starting temperature is higher than the threshold value or operating a variable valve timing unit for a catalyst preheating time to advance an exhaust valve open time by a predetermined angle per 1 cycle if lower, and returning the exhaust valve open time to a normal state and finishing the control after the catalyst preheating time.
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