PURPOSE: To avoid an engine output from abrupt change when the supply and shut-off of assist air are changed over.
CONSTITUTION: When a requirement for shutting off 16 assist air 15 is established, an ignition timing is delayed by a certain angle (S3). While the assist air is shut off (S5) when the total delay angle correction amount reaches a predetermined value, the ignition timing subjected to the delay angle correction is returned to the basic ignition timing (S6). Since the process for returning the ignition timing subjected to the delay angle correction to the basic ignition timing is the correction for advancing the ignition timing, the reduction of output caused by the shut-off of the assist air can be restrained by the advance angle correction.
MIYATA MITSURU
SHIMIZU HIROKAZU
NANBA TOSHIO
