PURPOSE: To prevent a flame from being blown out or the like, by constituting a device so as to enable a swirl generating function by a swirl generating means to be suppressed when a mixture in a combustion chamber is in a temperature of predetermined value or less, in the case of an engine which generates a swirl when the engine is in low load operation.

CONSTITUTION: An intake port 4 is partitioned into a primary port 4A for use of low speed and low load and a secondary port 4B for use of high speed and high load. And in a low speed and low load operation condition, an engine, which closes a swirl control valve 13 in the secondary port 4B performing an intake from the primary port 4A provided being offset a predetermined angle with respect to the center of a combustion chamber, generates a swirl. Here the engine provides the first and second water temperature thermistors 26, 27, and when a mixture in the combustion chamber, detected from outputs of these thermistors, is in a temperature of predetermined value or less, the engine suppresses the generation of the swirl by opening the swirl control valve 13 even in a region of generating the swirl.