Four-stroke internal combustion engine and method of controlling timings of an exhaust camshaft and an intake camshaft

A vehicle comprising a four-stroke internal combustion engine comprising at least one cylinder arrangement, a crankshaft, an exhaust camshaft, an intake camshaft, a turbocharger, and a control system, wherein the cylinder arrangement comprises a combustion chamber, a cylinder bore, a piston configured to reciprocate in the cylinder bore and being connected to the crankshaft, an exhaust valve, and an intake valve, wherein the exhaust camshaft is configured to control the opening and closing of the exhaust valve, and the intake camshaft is configured to control the opening and closing of the intake valve, wherein the turbocharger comprises a compressor and a turbine, the turbine being arranged in an exhaust gas flow path extending from the exhaust valve, wherein a timing of the exhaust camshaft and a timing of the intake camshaft are controllable by the control system, wherein the control system is configured to:

• store a compressor map related to the compressor of the turbocharger;
• store a reference area within the compressor map;
• determine at least two parameters out of:
• (i) a current turbocharger rotational speed, (ii) a current charge air mass flow, and (iii) one of a current charge air pressure or a current compressor pressure ratio;
• and
• in response to the at least two parameters indicating that a current operational point of the compressor is outside the reference area at a higher charge air mass flow than a maximum charge air mass flow of the reference area at a compressor pressure ratio of the current operational point:
• change the timing of the exhaust camshaft to advance closing of the exhaust valve;
• and
• change the timing of the intake camshaft to delay opening of the intake valve.

A method of controlling timings of an exhaust camshaft and an intake camshaft of a four-stroke internal combustion engine comprising at least one cylinder arrangement, a crankshaft, the exhaust camshaft, the intake camshaft, a turbocharger, and a control system, wherein the cylinder arrangement comprises a combustion chamber, a cylinder bore a piston configured to reciprocate in the cylinder bore and being connected to the crankshaft, an exhaust valve, and an intake valve, wherein the exhaust camshaft is configured to control the opening and closing of the exhaust valve, and the intake camshaft is configured to control the opening and closing of the intake valve, wherein the turbocharger comprises a compressor and a turbine, the turbine being arranged in an exhaust gas flow path extending from the exhaust valve, wherein the control system is configured to store a compressor map related to the compressor of the turbocharger, and to store a reference area within the compressor map, and wherein the method comprises steps of:

• determining at least two parameters out of:
• (i) a current turbocharger rotational speed, (ii) a current charge air mass flow, and (iii) one of a current charge air pressure or a current compressor pressure ratio;
• detecting whether the at least two parameters indicate that a current operational point of the compressor is outside the reference area at a higher charge air mass flow than a maximum charge air mass flow of the reference area at a compressor pressure ratio of the current operational point;
• and
• in response thereto perform steps of:
• changing the timing of the exhaust camshaft to advance closing of the exhaust valve;
• and
• changing the timing of the intake camshaft to delay opening of the intake valve.

A non-transitory computer-readable storage medium comprising computer program instructions stored thereon for controlling timings of an exhaust camshaft and an intake camshaft of a four-stroke internal combustion engine comprising at least one cylinder arrangement, a crankshaft, the exhaust camshaft, the intake camshaft, a turbocharger, and a control system, wherein the cylinder arrangement comprises a combustion chamber, a cylinder bore, a piston configured to reciprocate in the cylinder bore and being connected to the crankshaft, an exhaust valve, and an intake valve, wherein the exhaust camshaft is configured to control the opening and closing of the exhaust valve, and the intake camshaft is configured to control the opening and closing of the intake valve, wherein the turbocharger comprises a compressor and a turbine, the turbine being arranged in an exhaust gas flow path extending from the exhaust valve, wherein the control system is configured to store a compressor map related to the compressor of the turbocharger, and to store a reference area within the compressor map, said computer program instructions configured to cause one or more control devices to perform the following operations:

• determining at least two parameters out of:
• (i) a current turbocharger rotational speed, (ii) a current charge air mass flow, and (iii) one of a current charge air pressure or a current compressor pressure ratio;
• detecting whether the at least two parameters indicate that a current operational point of the compressor is outside the reference area at a higher charge air mass flow than a maximum charge air mass flow of the reference area at a compressor pressure ratio of the current operational point;
• and
• in response thereto perform steps of:
• changing the timing of the exhaust camshaft to advance closing of the exhaust valve;
• and
• changing the timing of the intake camshaft to delay opening of the intake valve.