Systems and methods for operating an engine with deactivating and non-deactivating valves are presented. In one example, valves of a cylinder are deactivated in a closed state in response to an indication of degradation of a valve of the cylinder. Further, fuel flow to the cylinder may be stopped via ceasing to inject fuel to the cylinder.

Systems and methods for operating an engine with deactivating and non-deactivating valves are presented. In one example, valves of a cylinder are deactivated in a closed state in response to an indication of degradation of a valve of the cylinder. Further, fuel flow to the cylinder may be stopped via ceasing to inject fuel to the cylinder.

An internal combustion engine having an engine control configured to operate in first and second operating modes. The first operating mode is configured to leave as many ignition devices deactivated per cycle in dependence on the currently present power demand. The second operating mode is configured to reduce a risk of deflagration due to unburned gas-air mixture present in an exhaust stroke. After a first number (N.sub.1) of cycles, for a second number (N.sub.2) of cycles, the second operating mode has more piston-cylinder units produce power per cycle than required for the currently present power demand. After the second number (N.sub.2) of cycles, for a third number (N.sub.3) of cycles, in dependence on a currently present power demand per cycle, the second operating mode has so many piston-cylinder units produce power that this results in a torque of the crankshaft adapted to the currently present power demand.

An internal combustion engine having an engine control configured to operate in first and second operating modes. The first operating mode is configured to leave as many ignition devices deactivated per cycle in dependence on the currently present power demand. The second operating mode is configured to reduce a risk of deflagration due to unburned gas-air mixture present in an exhaust stroke. After a first number (N.sub.1) of cycles, for a second number (N.sub.2) of cycles, the second operating mode has more piston-cylinder units produce power per cycle than required for the currently present power demand. After the second number (N.sub.2) of cycles, for a third number (N.sub.3) of cycles, in dependence on a currently present power demand per cycle, the second operating mode has so many piston-cylinder units produce power that this results in a torque of the crankshaft adapted to the currently present power demand.

Systems and methods are provided for cooling an overheated engine using a combination of variable displacement engine (VDE) technology and direct injection technology. In one example, a method may include deactivating a subset of engine cylinders based on an engine temperature and directly injecting liquid fuel into the deactivated cylinders. In this way, an increased thermal conductivity of the liquid fuel compared to air decreases the engine temperature at a faster rate than when air-based engine cooling methods are used, thereby preventing overheating-related engine degradation.

Systems and methods are provided for cooling an overheated engine using a combination of variable displacement engine (VDE) technology and direct injection technology. In one example, a method may include deactivating a subset of engine cylinders based on an engine temperature and directly injecting liquid fuel into the deactivated cylinders. In this way, an increased thermal conductivity of the liquid fuel compared to air decreases the engine temperature at a faster rate than when air-based engine cooling methods are used, thereby preventing overheating-related engine degradation.

Methods and systems are provided for providing secondary air to an exhaust system during catalyst warm-up. In one example, a method may include, during a cold start condition, operating an engine with a first number of cylinders unfired and a remaining number of cylinders fired during an engine cycle, opening an intake valve of an unfired cylinder of the first number of cylinders during an expansion stroke of the unfired cylinder, and opening an exhaust valve of the unfired cylinder during a compression stroke of the unfired cylinder. In this way, the unfired cylinders may provide the secondary air to the exhaust system during a stroke that increases mixing of the secondary air with burned exhaust gas from fired cylinders, thus increasing exotherm production in the exhaust system to increase a temperature of the catalyst.

Methods and systems are provided for providing secondary air to an exhaust system during catalyst warm-up. In one example, a method may include, during a cold start condition, operating an engine with a first number of cylinders unfired and a remaining number of cylinders fired during an engine cycle, opening an intake valve of an unfired cylinder of the first number of cylinders during an expansion stroke of the unfired cylinder, and opening an exhaust valve of the unfired cylinder during a compression stroke of the unfired cylinder. In this way, the unfired cylinders may provide the secondary air to the exhaust system during a stroke that increases mixing of the secondary air with burned exhaust gas from fired cylinders, thus increasing exotherm production in the exhaust system to increase a temperature of the catalyst.

A method and system for operating a hybrid vehicle that includes an integrated starter/generator and a driveline disconnect clutch is described. In one example, the method determines whether or not to rotate an engine via an electric machine while propelling a vehicle via the electric machine according to vehicle efficiency.

A method and system for operating a hybrid vehicle that includes an integrated starter/generator and a driveline disconnect clutch is described. In one example, the method determines whether or not to rotate an engine via an electric machine while propelling a vehicle via the electric machine according to vehicle efficiency.