FIELD: engine devices and pumps.
SUBSTANCE: diagnostics system includes a cylinder pressure sensor and an ECU. The ECU is configured to: (a) determine whether each cylinder from an estimated target cylinder group is the cylinder with a lean mixture; (b) assess the degree of lean air/fuel ratio of the available lean-mix cylinders when the lean-mix cylinders are available in the estimated target group; (c) compute polytrope index in the expansion stroke for each cylinder; (d) correlate the information on the relation to define the ratio between the value of the polytrope in the expansion stroke and the value of the air/fuel ratio with a polytrope index in the expansion stroke of the lean-mix support cylinder; and (e) calculate the difference in air/fuel ratio between the cylinders on the basis of the polytrope index of the supporting cylinder with the lean mixture, information on ratio correlated with the polytrope index of the supporting cylinder with lean mixture.
EFFECT: possibility to calculate the air/fuel difference between cylinders or calculate the value of the air/fuel ratio using the cylinder pressure sensor even in the area where the air/fuel ratio is below the theoretical ratio.
9 cl, 11 dwg
