Abstract
In a knock control system, a threshold value must be chosen for the system to take action such as retarding the timing. This paper proposes a method of determining the threshold value by using a statistical treatment of a limited number of knock intensities from a simple experiment. The experiment consists of running an engine in a fixed condition (spark advance, speed and load) for several hundreds of cycles while measuring the knock intensity of every cycle. The spark advance is then increased in steps through an audible knock onset and the knock intensities are measured for each step. The results are treated statistically in order to determine the threshold value of knock intensity at which knock starts. The method is especially important in determining the knock onset in a noisy operating condition where the knock onset is difficult to determine by ear.