Internal combustion engine with dilution reduction in response to surge detection

Claim 1

A dilution control for an internal combustion engine having a plurality of combustion chambers in which fuel charges are ignited in a predetermined order, a rotating crankshaft and a dilution control mechanism controllable to vary the dilution gas content of the fuel charge according to a predetermined schedule, comprising in combination: first means effective to detect the time duration of a constant predetermined crankshaft rotational angle during the period of crankshaft deceleration before top dead center (BTDC) for each consecutively ignited combustion chamber; second means effective to update an average time duration with selected periodic time durations detected by the first means; third means effective to compute the difference between selected periodic time durations detected by the first means and the average time duration; fourth means effective to detect zero crossings of successive differences as computed by the third means and derive therefrom the period and therefore the frequency of said zero crossings; fifth means effective to compute and store each new maximum value of the difference as computed by the third means between zero crossings as detected by the fourth means and thereby detect the maximum value of the differences between said zero crossings; sixth means effective, for selected periodic zero crossings, to generate a surge signal if the period of said zero crossing as derived by the fourth means corresponds to a predetermined frequency range of substantially 2 to 10 Hz and if the maximum difference as detected by the fifth means is greater than a predetermined reference; and seventh means effective to decrease dilution from the predetermined schedule in response to said surge signal and allow dilution to return to the predetermined schedule in the absence of the surge signal.