Abstract: A control system for a compression-ignition engine is provided, which includes an engine configured to combust a mixture gas inside a combustion chamber by compression ignition, a fuel injector attached to the engine, a state function adjusting part attached to the engine and configured to adjust at least introduction of fresh air into the combustion chamber, a three-way catalyst provided in an exhaust passage of the engine, a wall temperature acquiring part configured to acquire a parameter related to a temperature of a wall of the combustion chamber, and a controller. A swirl flow is generated inside the combustion chamber to circle along the wall. When the wall temperature of the combustion chamber is below a given wall temperature, the controller sets an air-fuel ratio of the mixture gas substantially to a stoichiometric air-fuel ratio so as to remain within a purification window of the three-way catalyst.

Abstract: A PCM (100) selects one of a CI mode or an SI mode based on the operating conditions of the engine (1). In the CI mode, the engine (1) is operated by compression ignition combustion. In the SI mode, the engine (1) is operated by spark ignition combustion. if, while the engine (1) is being operated in the CI mode, a determination is made that an estimated value (Tc) of the catalyst temperature is lower than or equal to a warming start temperature (Ts), the PCM (100) further performs first warming control to assign four cylinders (18) as CI and SI cylinders, which perform the compression ignition combustion and the spark ignition combustion, respectively, such that the four cylinders (18) alternately perform the compression ignition combustion and the spark ignition combustion in accordance with the order of combustion of the cylinders.