An engine system comprises an intake manifold including a manifold body downstream of an intake port and having a first through-aperture and a second through-apertures spaced apart from the first through-aperture on the manifold body; a positive crankcase ventilation (PCV) system including a first PCV branch and a second PCV branch communicated fluidly with the first through-aperture and the second through-aperture of the manifold body, respectively, and configured to route a blow-by gas in a crankcase to the intake manifold; and a variable valve assembly to regulate a flow passing through the first or second PCV branches.

Methods and systems are provided for estimating a PCV flow to an engine based on the output of an exhaust gas oxygen sensor. During DFSO conditions, a reference voltage of the sensor is modulated initially with an intake throttle open and then with the intake throttle closed. PCV flow leaking past the piston valves in an aging engine, as well as an ambient humidity estimate, are inferred based on the outputs of the sensor during the modulating with the intake throttle open and closed.

A sensor circuit for a positive crankcase ventilation (PCV) valve includes an electrical source, a measuring circuit, a position calculator, and a transmitter. The electrical source is configured to apply an electrical bias across a spring of the PCV valve. The electrical bias is applied between a first end of the spring and an opposite end of the spring. The measuring circuit is configured to measure a value of an electrical parameter of the spring while the electrical bias is applied. The electrical parameter indicates at least one of a voltage across the spring and a current through the spring. The position calculator is configured to calculate an inductance of the spring based on the value of the electrical parameter and calculate a position of the PCV valve based on the inductance. The transmitter is configured to output a signal that indicates the position of the PCV valve.

Methods and arrangements for transitioning an engine between a deceleration cylinder cutoff (DCCO) state and an operational state are described. In one aspect, transitions from DCCO begin with reactivating cylinders to pump air to reduce the pressure in the intake manifold prior to firing any cylinders. In another aspect, transitions from DCCO, involve the use of an air pumping skip fire operational mode. After the manifold pressure has been reduced, the engine may transition to either a cylinder deactivation skip fire operational mode or other appropriate operational mode. In yet another aspect a method of transitioning into DCCO using a skip fire approach is described. In this aspect, the fraction of the working cycles that are fired is gradually reduced to a threshold firing fraction. All of the working chambers are then deactivated after reaching the threshold firing fraction.

In a multi-fuel system for diesel engines, natural gas is mixed with diesel fuel and conditioned in a mixing chamber before being injected into the mixing chamber of the engine. Filtered blow-by gas may also be introduced into the combustion chamber. A computerized controller is used to determine and control the proportion of diesel fuel, natural gas fuel, the mixing and conditioning of these fuels, and the supply of filtered blow-by gas.

A method is provided for detecting fuel discharge from a lubricant in a housing of an internal combustion engine. A first lambda deviation is measured by a lambda sensor for a first mass air flow supplied in an intake tract of the engine. A second lambda deviation is measured by the lambda sensor for a second mass air flow that differs from the first mass air flow, and is supplied in an intake tract of the engine. An actual comparative value is calculated from the measured first and second lambda deviations. A desired comparative value indicative of the fuel discharge is calculated from a first desired lambda deviation for the first mass air flow, and a second desired lambda deviation is calculated for the second mass air flow. The fuel discharge is detected based on a comparison of the actual comparative value and the desired comparative value.

An internal combustion engine has a control device, an EGR valve that adjusts an EGR rate, a PCV valve that adjusts an opening degree of a first PCV passage that communicates an inside of a crankcase and a downstream side of a throttle valve. The control device operates the throttle valve in a closing direction in response to a deceleration request. The control device adjusts an opening degree of the PCV valve based on an immediately preceding EGR rate immediately before reception of the deceleration request.

A learned neural network learned in weights using an engine load, an engine speed, and an intake pressure inside the engine intake passage downstream of the throttle valve (19) as input parameters of the neural network and using leakage of blow-by gas from a blow-by gas feed path (20) as a truth label is stored. At the time of operation of the vehicle, the learned neural network is used to detect the abnormality of leakage of blow-by gas from the blow-by gas feed path (20) from the above input parameters.

Methods and arrangements for transitioning an engine between a deceleration cylinder cutoff (DCCO) state and an operational state are described. In one aspect, transitions from DCCO begin with reactivating cylinders to pump air to reduce the pressure in the intake manifold prior to firing any cylinders. In another aspect, transitions from DCCO, involve the use of an air pumping skip fire operational mode. After the manifold pressure has been reduced, the engine may transition to either a cylinder deactivation skip fire operational mode or other appropriate operational mode. In yet another aspect a method of transitioning into DCCO using a skip fire approach is described. In this aspect, the fraction of the working cycles that are fired is gradually reduced to a threshold firing fraction. All of the working chambers are then deactivated after reaching the threshold firing fraction.

Methods, systems, and computer program products are provided for controlling an internal combustion that comprises a cylinder having a space arranged to receive air and fuel, a piston disposed in the cylinder, and a crankcase being in fluid communication with the cylinder. The method comprises determining an uncontrolled behavior due to fluid flow between said crankcase and said cylinder space and combustion of such fluid, which entails: determining whether a powertrain of the vehicle is disengaged; determining whether the engine speed is increasing; and determining whether said cylinder space is receiving fuel. The method further comprises determining that an uncontrolled behavior is occurring if the conditions that: said powertrain is disengaged, the engine speed is increasing and said cylinder space is not receiving any fuel, are fulfilled.