A single-turbocharged engine system, comprising: an internal combustion engine having a plurality of cylinders, wherein the engine cylinders are divided into a first sub-group of cylinders and a second sub-group of cylinders; an exhaust manifold system comprising a main exhaust manifold that receives exhaust gases from the second sub-group of cylinders, and a bypass exhaust manifold that receives exhaust gases from the first sub-group of cylinders; a bypass line coupled to the bypass exhaust manifold to receive exhaust gases therefrom; an exhaust gas feed conduit coupled to the main exhaust manifold to receive exhaust gases therefrom; a single turbocharger comprising a compressor and a turbine, the turbine comprising an exhaust gas inlet coupled to the exhaust gas feed conduit to receive exhaust gases therefrom, and comprising an exhaust gas discharge conduit for discharging exhaust gases that have passed through the turbine, a downstream end of the bypass line being coupled to the exhaust gas discharge conduit at a position downstream of the turbine; and a partial-engine bypass valve system disposed between the engine cylinders and the turbocharger, the partial-engine bypass valve system comprising a three-way valve having a valve inlet, a first outlet and a second outlet, wherein the valve inlet is coupled to the bypass exhaust manifold to receive exhaust gases therefrom, the first outlet is coupled to the main exhaust manifold to supply exhaust gases thereinto, and the second outlet is coupled to an upstream end of the bypass line, the three-way valve being adjustable to a non-bypass position in which a flow path is opened from the valve inlet to the first outlet whilst the second outlet is closed, thereby establishing fluid communication between the bypass exhaust manifold and main exhaust manifold while preventing exhaust gases from flowing from any of the engine cylinders to the bypass line via the bypass exhaust manifold, such that the exhaust gases from all engine cylinders commingle and pass through the exhaust gas feed conduit for supply to the turbine, the three-way valve being alternatively adjustable to a bypass position in which a flow path is opened from the valve inlet to the second outlet whilst the first outlet is closed, thereby fluidly isolating the bypass exhaust manifold from the main exhaust manifold and allowing exhaust gases from the first sub-group of engine cylinders to bypass the turbine wheel and proceed directly into the exhaust gas discharge conduit whilst exhaust gases from the second sub-group of cylinders flow into the main exhaust manifold for supply to the turbine. an internal combustion engine having a plurality of cylinders, wherein the engine cylinders are divided into a first sub-group of cylinders and a second sub-group of cylinders; an exhaust manifold system comprising a main exhaust manifold that receives exhaust gases from the second sub-group of cylinders, and a bypass exhaust manifold that receives exhaust gases from the first sub-group of cylinders; a bypass line coupled to the bypass exhaust manifold to receive exhaust gases therefrom; an exhaust gas feed conduit coupled to the main exhaust manifold to receive exhaust gases therefrom; a single turbocharger comprising a compressor and a turbine, the turbine comprising an exhaust gas inlet coupled to the exhaust gas feed conduit to receive exhaust gases therefrom, and comprising an exhaust gas discharge conduit for discharging exhaust gases that have passed through the turbine, a downstream end of the bypass line being coupled to the exhaust gas discharge conduit at a position downstream of the turbine; and a partial-engine bypass valve system disposed between the engine cylinders and the turbocharger, the partial-engine bypass valve system comprising a three-way valve having a valve inlet, a first outlet and a second outlet, wherein the valve inlet is coupled to the bypass exhaust manifold to receive exhaust gases therefrom, the first outlet is coupled to the main exhaust manifold to supply exhaust gases thereinto, and the second outlet is coupled to an upstream end of the bypass line, the three-way valve being adjustable to a non-bypass position in which a flow path is opened from the valve inlet to the first outlet whilst the second outlet is closed, thereby establishing fluid communication between the bypass exhaust manifold and main exhaust manifold while preventing exhaust gases from flowing from any of the engine cylinders to the bypass line via the bypass exhaust manifold, such that the exhaust gases from all engine cylinders commingle and pass through the exhaust gas feed conduit for supply to the turbine, the three-way valve being alternatively adjustable to a bypass position in which a flow path is opened from the valve inlet to the second outlet whilst the first outlet is closed, thereby fluidly isolating the bypass exhaust manifold from the main exhaust manifold and allowing exhaust gases from the first sub-group of engine cylinders to bypass the turbine wheel and proceed directly into the exhaust gas discharge conduit whilst exhaust gases from the second sub-group of cylinders flow into the main exhaust manifold for supply to the turbine.