is coupled with a physical model representing the expulsion of the gases from the cylinders and their travel in the exhaust circuit to the detector the method has application to engine controls application_number US 43762906 A description the exhaust process comprises the path travelled by the gases from the exhaust valve to the open air at the exhaust silencer outlet the engine in the present embodiment example is a 2200 cm 3 4 cylinder engine it is equipped with a variable geometry turbosupercharger the diagram of fig1 shows the descriptive elements of the exhaust process wherein u03bb 1 to u03bb 4 are the fuel air ratios in each one of the four cylinders ds 1 to ds 4 represent the flow rates at the cylinder outlets fuel air ratio probe sr is arranged just after turbine t the gases after combustion in the cylinder undergo the following actions passage through the exhaust valve the latter being controlled by a camshaft the lift law is bell shaped the flow rates will go from a high value when the valve opens to a lower value when the cylinder and manifold pressures become equal and they will eventually increase again when the piston starts to slide up again to expel the exhaust gases passage through a short pipe connecting the manifold to the cylinder head outlet a mixing phase in exhaust manifold ce where the flows ds 1 to ds 4 from the four cylinders meet it is here that the puffs of.