To provide a control method for preventing change in engine performance against change in cetane number, by indirectly determining the cetane number by means of an inexpensive sensor, in a compression self-ignition type diesel engine.

Under a predetermined operating condition, engine exciting force by pressure inside cylinder is detected by an exciting force detection means having a piezoelectric element, and the cetane number corresponding to the detected exciting force is determined based on correlation data between the exciting force and the cetane number prepared in advance under the same operating condition, so that an engine control is performed based on the determined cetane number. The cetane number is determined indirectly from exciting force generation timing, an engine speed, CO concentration in exhaust, and torque or the like, in place of the exciting force. Accordingly, an ignition delay period is corrected to be shorten, particularly in low cetane number, to prevent generation of white smoke or irritating odor.

COPYRIGHT: (C)2005,JPO&NCIPI