Patent ID: 7313918

Claim:
A method of operating a 4-stroke reciprocating engine wherein the engine is operating between a minimum speed of rotation Nmin and a maximum speed Nmax and comprises: a turbocharging unit comprising: a compressor which supplies an intake manifold of the engine with compressed air via a cooler; a turbine which is supplied with a hot exhaust gas by an exhaust manifold of the engine at an exhaust temperature, the turbine defining an exhaust outlet section Sd offered to said hot exhaust gas; and an EGR bypass provided between the intake manifold and the exhaust manifold which EGR bypass is dimensioned to transfer a flow of gas between the intake manifold and the outlet manifold without substantial loss of pressure, such that a turbine inlet pressure substantially equal to a compressor discharge pressure; such that, at constant air temperature and with a constant value of the exhaust outlet section Sd, the turbocharging unit delivers a substantially constant volume of cooled air Vc when the compressor discharge pressure varies, the constant volume of cooled air Vc being substantially proportional to the exhaust outlet section Sd offered to the hot exhaust gas, wherein the exhaust outlet section Sd is selected such that at a turbocharging adaptation speed Na, the volume drawn in by the engine is equal to the constant volume Vc, below the turbocharging adaptation speed Na, the volume drawn in by the engine is less than the constant volume of cooled air Vc, and a flow of the cooled air is deflected toward the turbocharging unit through the EGR bypass, and above the turbocharging adaptation speed Na and including the maximum speed Nmax, the volume drawn in by the engine is more than the constant volume of cooled air Vc, and a flow of exhaust gas is drawn in by the engine through the EGR bypass, wherein the EGR bypass has a gas cooler adjustable to control the temperature of the transferred flow of the hot exhaust gas, and wherein the method of operating includes controlling the EGR bypass temperature to create a desired excess of air for combustion in the engine; and wherein the exhaust outlet section Sd is selectively variable and is controlled: at full load, to maintain a parameter at a limiting desired value thereof; and at partial load, to optimize depollution and/or performance according to a map stored in an engine control computer.