Fuel management system for enhanced operation of a spark ignition gasoline engine. Injectors inject an anti-knock agent such as ethanol directly into a cylinder. It is preferred that the direct injection occur after the inlet valve is closed. It is also preferred that stoichiometric operation with a three way catalyst be used to minimize emissions. In addition, it is also preferred that the anti-knock agents have a heat of vaporization per unit of combustion energy that is at least three times that of gasoline.

A concentration of sulfur components contained in fuel is determined, without adding any special sensor for determining the sulfur concentration of the fuel. To this end, a sulfur concentration determination system for an internal combustion engine is provided with an exhaust gas purification device including an oxidation catalyst disposed in an exhaust passage, and a supply device for supplying fuel to exhaust gas flowing into the exhaust gas purification device, wherein after the end of poisoning elimination processing of the oxidation catalyst, fuel supply processing is carried out in which the fuel is supplied to the exhaust gas purification device in such a manner that an amount of fuel supplied to the exhaust gas purification device per unit time becomes constant, and the concentration of sulfur components contained in the fuel is determined by using as a parameter a period of time (an oxidation reaction period of time) required from a starting point in time of the fuel supply processing until the temperature of the oxidation catalyst drops to an initial temperature or below.

In a method and an arrangement for determining a fuel quality of a fuel for a combustion engine fuel is conveyed from a low pressure fuel tank to a high-pressure volume, and injected into at least one cylinder of the combustion engine. A control valve is provided for controlling directly or indirectly the amount of fuel injected into the at least one cylinder. An actual value of a timing signal of the control valve is compared to a reference value of the timing signal of the control valve and a fuel quality parameter is derived from a difference between the actual value and the reference value of the timing signal of the control valve and/or that a fuel quality parameter is derived from a gradient of the pressure increase during a build-up phase of the pressure in the high-pressure volume compared to a reference value of the gradient of the pressure increase in the high-pressure volume.

A method for detecting the anti-knocking capacity of a fuel in an internal combustion engine, which comprises the step of analyzing the single combustion cycles of the cylinders to be repeated until a counter reaches a respective threshold value; the step of calculating the mean spark advance operated by the internal combustion engine in the single combustion cycles of the cylinders that have allowed said counter to reach the respective threshold value; and the step of determining the anti-knocking capacity of the fuel as a function of the first counter that has reached the respective threshold value and as a function of the mean spark advance operated by the internal combustion engine in the single combustion cycles of the cylinders that have allowed said counter to reach the respective threshold value.

A method for controlling an air-fuel ratio (AFR) in an engine powered by a gaseous fuel having an unknown composition may comprise receiving an assumed gas species composition for the gaseous fuel, and determining an assumed lower heating value (LHV) for the assumed gas species composition. The method may further comprise determining a perceived lower heating value (LHV) for the gaseous fuel based on a perceived gas mass flow and a gas energy flow for the gaseous fuel, and updating the assumed gas species composition until the assumed LHV and the perceived LHV are aligned. The method may further comprise determining a desired AFR and an airflow necessary to provide the desired AFR using the aligned gas species composition and a desired lambda (), and adjusting an air system controller of the engine to provide the airflow.

A fuel tank containing a fuel and oil mixture is managed to determine if the fuel and oil mixture contains the correct ratio for a motor. The fuel tank containing a fuel and oil mixture is monitored. A fuel to oil ratio is selected for the motor. A combined viscosity of the fuel and oil mixture is calculated with respect to the fuel to oil ratio, and the temperature of the fuel and oil mixture. The combined viscosity is used to determine a predetermined range of the combined viscosity. The viscosity of the fuel and oil mixture within the fuel tank is measured as a measured viscosity. If the measured viscosity of the fuel and oil mixture does not correspond with the predetermined range, then a user may be alerted that the measured viscosity does not correspond with the predetermined range.

A fuel tank containing a fuel and oil mixture is managed to determine if the fuel and oil mixture contains the correct ratio for a motor. The fuel tank containing a fuel and oil mixture is monitored. A fuel to oil ratio is selected for the motor. A combined viscosity of the fuel and oil mixture is calculated with respect to the fuel to oil ratio, and the temperature of the fuel and oil mixture. The combined viscosity is used to determine a predetermined range of the combined viscosity. The viscosity of the fuel and oil mixture within the fuel tank is measured as a measured viscosity. If the measured viscosity of the fuel and oil mixture does not correspond with the predetermined range, then a user may be alerted that the measured viscosity does not correspond with the predetermined range.

This fuel property estimation device is used in an internal combustion engine that uses a mixed fuel of three kinds of fuel and includes a first sensor that outputs a signal responsive to a physical property of the fuel in a fuel route and a second sensor outputs a signal responsive to an oxygen concentration of exhaust gas. This device measures a physical property value of the mixed fuel based on a first sensor signal, and calculates an air-fuel ratio value at stoichiometric combustion state using feedback of a second sensor signal. This device estimates a composition ratio of the mixed fuel based on the measured physical property value and the calculated air-fuel ratio value by referring to a relationship between the composition ratio of the mixed fuel and the physical property value and a relationship between the composition ratio of the mixed fuel and a theoretical air-fuel ratio value.

A method for estimating a specific gravity of a gaseous fuel is described. The gaseous fuel may power an engine and the engine may include a cylinder, a gas valve configured to supply an intake port of the cylinder with the gaseous fuel, a gas rail configured to deliver the gaseous fuel to the gas valve, and a microprocessor adapted to perform the method. The method may comprise establishing a pressure wave in the gas rail by opening and closing the gas valve, wherein the pressure wave travels at the speed of sound in the gaseous fuel. The method may further comprise determining a frequency of the pressure wave in the gas rail, and estimating the specific gravity of the gaseous fuel based on the frequency of the pressure wave.

In a control system for an internal combustion engine that can use a plurality of kinds of fuel including compressed natural gas, the invention prohibits a changeover from CNG to another fuel from being made in a period from a time when CNG is used for the first time after the start of the internal combustion engine to a time when it is determined that properties of CNG do not need to be learned, or a period from the time when CNG is used for the first time after the start of the internal combustion engine to a time when a processing of learning the properties of CNG ends.