Control system for compression ignition engine

A control system for a compression ignition engine configured to start compression ignition combustion by igniting mixture gas formed by injecting fuel into a plurality of combustion chambers, comprising:

• the plurality of combustion chambers defined in respective cylinders so that displacements of the combustion chambers change by respective pistons reciprocating;
• a throttle valve configured to adjust an amount of air supplied into the combustion chambers;
• ignition plugs disposed so as to be oriented toward the respective combustion chambers;
• injectors configured to inject fuel into the respective combustion chambers;
• a sensor having a plurality of measuring parts including an atmospheric-pressure detector configured to detect an atmospheric pressure, and configured to measure parameters related to operation of the engine to emit measurement signals;
• and
• a controller having a circuitry connected with the throttle valve, the injectors, the ignition plugs, and the sensor, and configured to perform a calculation in response to the measurement signals from the sensor, and output signals to the throttle valve, the injectors, and the ignition plugs,
• wherein when the controller determines that a predetermined condition is satisfied, the controller having the circuitry executes a lean compression ignition combustion control in which compression ignition combustion is performed at a given lean air-fuel ratio higher than a stoichiometric air-fuel ratio,
• wherein the predetermined condition is determined to not to be satisfied, the controller does not execute the lean compression ignition combustion control, and
• wherein the controller restricts the execution of the lean compression ignition combustion control when the controller determines that the atmospheric pressure is lower than a given threshold based on a signal outputted from the atmospheric-pressure detector regardless of whether the predetermined condition is determined to be satisfied.