The present invention describes a fuel-management system for minimizing particulate emissions in turbocharged direct injection gasoline engines. The system optimizes the use of port fuel injection (PFI) in combination with direct injection (DI), particularly in cold start and other transient conditions. In the present invention, the use of these control systems together with other control systems for increasing the effectiveness of port fuel injector use and for reducing particulate emissions from turbocharged direct injection engines is described. Particular attention is given to reducing particulate emissions that occur during cold start and transient conditions since a substantial fraction of the particulate emissions during a drive cycle occur at these times. Further optimization of the fuel management system for these conditions is important for reducing drive cycle emissions.

A method for operating an internal combustion engine having multiple cylinders. A warm-up operation is carried out after the internal combustion engine has been started, during which a speed of the internal combustion engine is limited to a limit value. The limit value is selected during the warm-up operation at least temporarily as a function of a starting temperature of the internal combustion engine.

A method, performed by a control device, for starting a combustion engine during free-wheeling with engine off is described. The method comprises a step of controlling the clutch to a partially closed state, thereby starting the combustion engine; a step of controlling the clutch to an open state when the combustion engine has started, but prior to the output shaft of the combustion engine has reached a rotational speed synchronized with the rotational speed of the input shaft of the gearbox; and a step of synchronizing the speed of the combustion engine to the speed of the input shaft of the gearbox through control of fuel injection to the combustion engine.

A method of controlling fuel injection subsequent to engine start, comprises: a) at, or after synchronization, in respect of a potential upcoming firing or injection event for a particular cylinder, determining or selecting a first injection profile; b) determining if there is sufficient time for the first injection profile to be implemented; and c) if so, implementing the said first injection profile with respect to said event.

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 system and method for a variable displacement internal combustion engine using different types of pneumatic cylinder springs on skipped working cycles to control engine and aftertreatment system temperatures are described. The system and method may be used to rapidly heat up the aftertreatment system(s) and/or an engine block of the engine following a cold start by using one or more different types of pneumatic cylinder springs during skipped firing opportunities. By rapidly heating the aftertreatment system(s) and/or engine block, noxious emissions such as hydrocarbons, carbon monoxide, NO.sub.x and/or particulates, following cold starts are significantly reduced.

Methods and systems are provided for heating a catalyst via a catalyst heater are presented. In one example, the catalyst may be heated to provide a minimum amount of time for the catalyst to reach a threshold temperature. In another example, the catalyst heater may be heated to minimize an amount of power that is used to heat the catalyst.

Systems and methods for operating an internal combustion engine that is included in a hybrid vehicle are described. In one example, the internal combustion engine is operated in a two stroke mode during cold starting to increase mass flow to an electrically heated catalyst so that engine emissions may be reduced.

Disclosed is a system for detecting an operating state of a vehicle engine. The system comprises: an input coupled to a power line of a vehicle; means to filter out relatively high frequency transient noise components of a signal received from the power line; a first detector for receiving the filtered signal and detecting when transient noise associated with the power line rises above a first threshold and generating a first detection signal in response thereto; a second detector for receiving the filtered signal and detecting when the transient noise falls below a second threshold, which is lower than the first threshold, and generating a second detection signal in response thereto; and means for generating a first output signal in response to the first detection signal and a second output signal in response to the second detection signal.

A split cycle internal combustion engine includes a combustion cylinder accommodating a combustion piston and a compression cylinder accommodating a compression piston. The engine also includes a controller arranged to receive an indication of a parameter associated with the combustion cylinder and/or a fluid associated therewith and to control an exhaust valve of the combustion cylinder in dependence on the indicated parameter to cause the exhaust valve to close during the return stroke of the combustion piston, before the combustion piston has reached its top dead centre position (TDC), when the indicated parameter is less than a target value for the parameter; and close on completion of the return stroke of the combustion piston, as the combustion piston reaches its top dead centre position (TDC), when the indicated parameter is equal to or greater than the target value for the parameter.