Exhaust gas recirculation system for a turbocharged engine

A method of decompression braking of a turbocharged multiple cylinder internal combustion engine having a cylinder head with intake and exhaust ports therein, at least one intake valve for each cylinder and at least one primary exhaust valve for each cylinder, an exhaust manifold, an intake manifold, a secondary exhaust port in the cylinder head for each cylinder, a secondary exhaust valve for each cylinder for admitting exhaust gas into the secondary exhaust port when open, and an EGR manifold in fluid communication with the secondary exhaust ports and the intake manifold through an EGR valve to recirculate exhaust gas to the intake manifold, the method of decompression braking comprising the steps of:

• diverting exhaust gas from the EGR manifold to the exhaust manifold;
• opening the secondary exhaust valve of each cylinder near the beginning of the expansion stroke for the cylinder;
• and
• holding each secondary exhaust valve open until later in the expansion stroke.

A method of operating a turbocharged internal combustion engine having multiple cylinders in either an exhaust gas recirculation (EGR) mode or an engine decompression braking mode, the engine having a cylinder head, at least one intake valve and at least one primary exhaust valve for each cylinder, an intake manifold between the turbocharger and the cylinder head and an exhaust manifold between the cylinder head and the turbocharger, the method comprising the steps of:

• operating the engine in the EGR mode by diverting a flow of exhaust gas from the cylinders to an EGR manifold by opening and closing a secondary exhaust valve in each cylinder during the expansion stroke in each cylinder;
• and
• directing the diverted flow of exhaust gas from the EGR manifold to the intake manifold through an EGR valve;
• and
• operating the engine in the decompression braking mode by diverting exhaust gas from the EGR manifold to the exhaust manifold;
• opening the secondary exhaust valve of each cylinder near the beginning of the expansion stroke for the cylinder;
• and
• holding each secondary exhaust valve open until later in the expansion stroke.

An internal combustion engine having multiple cylinders comprising:

• a cylinder head having intake and exhaust ports therein;
• an exhaust manifold in fluid communication with the exhaust ports for receiving exhaust gas therefrom;
• an intake manifold in fluid communication with the intake ports in the cylinder head for directing air to the cylinder head;
• and
• an exhaust gas recirculation (EGR) system comprising:
• an exhaust gas conduit connecting the exhaust manifold to the intake manifold;
• a cooler in the exhaust gas conduit to cool exhaust gas before delivery of the exhaust gas to the intake manifold;
• a first EGR valve in the exhaust gas conduit to regulate the flow of exhaust gas from the exhaust manifold through the cooler and to the intake manifold;
• and
• a bypass conduit including a bypass EGR valve between the exhaust manifold and the intake manifold operable to deliver exhaust gas to the intake manifold without passing the exhaust gas through the cooler.