Systems and methods for starting an engine of a hybrid vehicle are described. In one example, the method uses the engine to generate larger amounts of thermal energy while the engine is rotated under power of an electric machine. The systems and methods described herein may be applied to series and parallel hybrid vehicles.

Engine systems which are safer and have reduced risk of fire are desirable in a wide range of equipment markets. The present engine systems utilize sensors and control systems which reduce the probability of fire or spark exiting the exhaust system. The sensors may monitor a wide range of conditions within the exhaust system to alter the operating parameters of the engine to prevent ignition of objects adjacent the engine system during use. By altering operation of the engine, conditions such as exhaust temperature or unburned fuel can be controlled to minimize risk of undesired ignition.

Methods and systems are provided for maintaining efficiency of a catalyst that is positioned in an exhaust system downstream of an internal combustion engine. In one example, the catalyst may be heated via supplying fuel to a cylinder that does not combust the fuel. The fuel may be oxidized at the catalyst via excess oxygen in the exhaust system.

Systems and methods are provided for diagnosing cylinders in an engine. In one example, the method may include while receiving first feedback from a vibration sensor coupled to a first cylinder of the engine, perturbing the first cylinder during engine operation. Responsive to the first feedback indicating a first vibration level difference greater than or equal to a first threshold difference, a first indication of a first degradation condition of the first cylinder may be set, and thereafter the engine may be operated based on whether or not the first indication was set.

A system includes a fuel tank and a dehydration reactor that are configured to provide a primary fuel and a pilot fuel to a power system. The fuel tank is configured to store the primary fuel and is fluidly connected to a reactor feed line and a primary fuel line provide the primary fuel. The dehydration reactor is configured to receive the primary fuel via the reactor feed line and convert a portion of the primary fuel to the pilot fuel and a byproduct. The power system is configured to receive the pilot fuel from the dehydration reactor to initiate combustion of the primary fuel. The power system also includes a cylinder with an internal piston that receives the pilot fuel and the primary fuel, contains the combustion reaction, and generates power from the combustion reaction; and contains the combustion reaction. A pilot fuel injector provides the pilot fuel to the cylinder at a first time to initiate combustion and a primary fuel injector provides the pilot fuel to the cylinder at to generate power via the power system.

A method for diagnosing a plurality of lambda sensors which are arranged upstream of an exhaust gas catalytic converter in a plurality of exhaust gas banks of a multi-flow exhaust gas system of an internal combustion engine. An opposite lambda offset of the lambda sensors is identified (54) when a difference (ΔT) between a measured exhaust gas temperature (T.sub.measure) and a modeled exhaust gas temperature (T.sub.mod) downstream of the exhaust gas catalytic converter overshoots a threshold value (S).

Timing of HHO gas injection into a 4-stroke engine is optimized based on engine operating parameters to improve fuel economy.

A method for operating an exhaust gas sensor in an exhaust system of an internal combustion engine of a vehicle. The exhaust gas sensor includes a ceramic sensor element having at least one measuring electrode and a heating device. A binary dewpoint end signal is calculated, based on data which relate to the internal combustion engine and the exhaust gas sensor, which indicates whether or not the occurrence of liquid water in the exhaust system is still to be expected. Whenever the vehicle is turned off and the dewpoint end signal simultaneously has the value which signals that the occurrence of liquid water in the exhaust system is still to be expected, the sensor element is heated by its heating device to a temperature for a certain period of time in such a way that the sensor element dries.

Various methods and systems are provided for a multi-fuel capable engine. The system includes a liquid fuel system to deliver liquid fuel to an engine, a gaseous fuel system to deliver gaseous fuel to the engine, and a control system. The control system can control and test the liquid and gaseous fuel systems.

An engine test method that causes a computer to execute a process including, acquiring, by a processer on the computer, a first test pattern in which an operation variable that is used for an engine test is changed in time series, inputting, based on the first test pattern, a first operation variable to a mathematical model that represents a time series response of an engine obtained by inputting a test pattern as a simulation of the engine test, monitoring, as a first monitoring parameter of engine abnormality, at least one of an air excess ratio, pressure and temperature of an intake manifold, pressure and temperature of an exhaust manifold, and a maximum cylinder pressure rise rate that are obtained by inputting the first operation variable to the mathematical model, holding, when the first monitoring parameter exceeds a first threshold value, the first operation variable until the first monitoring parameter is less than the first threshold value, creating, a history of the first operation variable in the simulation as a second test pattern, monitoring, as a second monitoring parameter, at least one of the air excess ratio, the pressure and the temperature of the intake manifold, the pressure and the temperature of the exhaust manifold, and the maximum cylinder pressure rise rate that are obtained by inputting a second operation variable to a real engine based on the second test pattern, holding, when the second monitoring parameter exceeds a second threshold value, the second operation variable until the second monitoring parameter is less than the second threshold value, and acquiring, time series data of the second operation variable and a controlled variable.