When an operation state switches from a first operation region A to a second operation region B, the valve timing of an intake valve and an exhaust valve is switched upon switching of the operation state from the first operation region A to the second operation region B. When the operation state switches from the first operation region A to the second operation region B, the air-fuel ratio is switched after a first predetermined time T1 has elapsed since when the actual valve timing of the intake valve became a second intake valve timing and the actual valve timing of the exhaust valve became a second exhaust valve timing. In this way, it becomes possible to ensure ignition when the operation state switches.

Methods and systems are provided for improving efficiency of an exhaust gas after treatment system of a vehicle. In one example, a first group of engine cylinders is operated with a rich air-fuel ratio continuously while a second group of engine cylinders is operated with a lean air-fuel ratio continuously. The rich and lean exhaust gases from the two groups of engine cylinders may be oxidized within an exhaust gas after treatment system to improve catalyst efficiency.

Methods and systems are provided for reducing engine compression torque when an engine having a split exhaust system is spun unfueled. In one example, a method may include maintaining closed a blowdown exhaust valve of a cylinder, the blowdown exhaust valve coupled to a first exhaust manifold that directs gases from the cylinder to a catalyst, and opening a scavenge exhaust valve of the cylinder, the scavenge exhaust valve coupled to a second exhaust manifold that directs gases from the cylinder to an exhaust gas recirculation system. In this way, compression of gases within they cylinder is reduced while gas flow to the catalyst is prevented.

A system includes a three-way catalyst (TWC) sulfur load module, a cylinder/fuel cutoff module, a fuel control module, and a valve control module. The TWC sulfur load module is configured to determine an amount of sulfur deposited on a three-way catalyst of an engine in a vehicle. The cylinder/fuel cutoff module is configured to determine whether to enable deceleration cylinder cutoff (DCCO) based on the amount of sulfur deposited on the three-way catalyst. The fuel control module is configured to control a fuel injector to selectively stop fuel injection in the engine when DCCO is enabled. The valve control module is configured to selectively maintain intake and exhaust valves of the engine in a closed position when DCCO is enabled.

A method for operating an internal combustion engine having a cylinder, an intake valve, an air pipe, and a valve element disposed in the air pipe, includes detecting a signal for causing a fuel supply of the cylinder to switch off. The valve element is moved out of a first position into a second position triggering a lower flow cross-section while the fuel supply is still activated, where a first cam for actuating the intake valve is allocated to the intake valve. While the fuel supply is still activated, switching from the first cam to a second cam and via the second cam the intake valve is actuated such that the intake valve causes a reduced air intake. An exhaust cam shaft for actuating an exhaust valve is set in an advance direction such that a valve intersection of the intake valve and of the exhaust valve ceases.

A method for controlling the air-fuel ratio of a vehicle includes: calculating the air amount charged in a cylinder of an engine by using a fresh air amount, a residual air amount remaining inside the cylinder of the engine, and a backflow gas amount flowing back into the cylinder upon the valve overlap of an intake vale and an exhaust valve of the engine, correcting it with the purge gas flow rate supplied to an intake manifold of the engine when the active purge system is operated, calculating the final fuel amount by correcting the fuel amount injected by a fuel injection device with the amount of the fuel component contained in the purge gas when the active purge system is operated, and controlling the air-fuel ratio based on the final air amount and the final fuel amount.

Methods and systems are provided for improving fuel vapor storage canister purging operations for vehicles with dual-path purge systems. In one example, a method may include purging fuel vapors from a fuel vapor storage canister to an engine of a vehicle via a single path, and in response to an unmetered increase in a concentration of the fuel vapors being purged to the engine via the single path, switching the fuel vapors to be purged to the engine via two paths simultaneously. In this way, fuel vapors may be distributed in time along the two paths, which may lower an effective concentration of fuel vapors entering the engine and may thereby avoid degradation of engine operating conditions.

When an operation state switches from a first operation region A to a second operation region B, the valve timing of an intake valve and an exhaust valve is switched upon switching of the operation state from the first operation region A to the second operation region B. When the operation state switches from the first operation region A to the second operation region B, the air-fuel ratio is switched after a first predetermined time T1 has elapsed since when the actual valve timing of the intake valve became a second intake valve timing and the actual valve timing of the exhaust valve became a second exhaust valve timing. In this way, it becomes possible to ensure ignition when the operation state switches.

An apparatus comprises a first circuit and a second circuit. The first circuit is structured to determine that a combustion cylinder is operating in a transition period between an exhaust stroke and an intake stroke of the combustion cylinder. The second circuit is structured to provide an injection command during the transition period to a fuel injector associated with the combustion cylinder, the injection command being to inject fuel into a combustion chamber of the combustion cylinder such that at least a portion of the fuel escapes from the combustion chamber through an exhaust port of the combustion cylinder.

Methods and systems for adjusting engine knock control system dynamic gains are presented. In one example, a plurality of tables or functions output gain values, each of which is adjusted via a unique weighting factor. A rectified and integrated engine knock sensor level is adjusted according to a sum of weighted gain output values of the plurality of tables or functions.