Abstract: A method for operating an internal combustion engine includes: providing a desired power specification for triggering the drive unit; providing a specification of operating point-dependent power ranges for the supplied desired power specification, in which steady-state operation of the drive unit is permissible, a power range that is not permissible in the steady state being defined between the operating point-dependent power ranges; when a change in the desired power specification for the drive unit in a transitional operating mode necessitates traversing the power range that is not permissible in the steady state, triggering the drive unit on the basis of a specification of a guided desired power, the guided desired power specification being determined by guiding the desired power specification.

Abstract: A device for controlling fuel injection in an internal combustion engine of an automobile, the internal combustion engine being connected at an inlet thereof to a fresh air intake pipe and at an outlet thereof to an exhaust gas discharge pipe including a catalytic converter, an exhaust gas partial recirculation circuit connecting the discharge pipe to the fresh air intake pipe. The device includes a mechanism determining the amount of unburned fuel in the exhaust gases, a mechanism determining the amount of fresh air taken into the internal combustion engine, and an electronic controller determining the amount of fuel to be injected depending on signals received of the determined amount of unburned fuel and the determined amount of fresh air taken in.

Abstract: An injection valve has a magnetic actuator and an injector needle able to be moved axially by the magnetic actuator. To meter a fluid by the injection valve the magnetic actuator is activated for an individual metering process with at least one actuation signal with a first or second signal waveform. The two actuation signals differ from one another in that, on activation of the magnetic actuator by the actuation signal with the first signal waveform, less energy is transmitted to a magnet unit of the magnetic actuator than during activation of the magnetic actuator by the actuation signal with the second signal waveform. The magnetic actuator is activated by the actuation signal with the second signal waveform if an activation of the magnetic actuator by the actuation signal with the first signal waveform leads to an undesired premature closure of the injector needle.

Abstract: An engine management system for a hybrid vehicle may include a hybrid vehicle controller that selects a power source to be one of an electric propulsion system and a combustion engine. The hybrid vehicle controller may include an engine operation module configured to determine when operation of the combustion engine is required based on a predetermined set of operating parameters associated with the combustion engine.

Abstract: A fuel injection control device for an engine executes a split injection constructed by a fixed injection and a variable injection. A required injection amount of the fixed injection is set in a low range. A required injection amount of the variable injection is set in a high range. An injection amount in the high range is larger than that of the low range. The required injection amount of the variable injection is changed within the high range while the required injection amount of the fixed injection is fixed when a load of the engine is varied while the split injection is performed. An injection control characteristic is corrected based on an actual air-fuel ratio detected before the load is varied and an actual air-fuel ratio detected after the load is varied.

Abstract: An air-fuel ratio control apparatus for an internal-combustion engine includes an air-fuel-ratio sensor, a control-input calculator, an air-fuel-ratio controller, and a gain calculator. The air-fuel-ratio sensor is disposed in an exhaust channel in the internal-combustion engine and is configured to detect an air-fuel ratio in exhaust gas. The control-input calculator is configured to calculate a control input in accordance with an output value of the air-fuel-ratio sensor. The air-fuel-ratio controller is configured to perform a feedback control using the control input such that the output value of the air-fuel-ratio sensor reaches a target value. The gain calculator is configured to calculate a gain in accordance with the output value when the output value is leaner than the target value. The gain is to be used in calculating the control input.

Abstract: In a method for controlling operation of an internal combustion engine using a control device, a setpoint value of a first fuel injection quantity is specified for a first combustion cycle, and the first fuel injection quantity is injected. A combustion pressure is ascertained during the first combustion cycle, and in a further step, a setpoint value of a second fuel injection quantity is ascertained for a second combustion cycle based on the combustion pressure.

Abstract: Methods are provided for controlling an engine in response to a pre-ignition event. A pre-ignition threshold and a pre-ignition mitigating action are adjusted based on a rate of change of cylinder aircharge. As a result, pre-ignition events occurring during transient engine operating conditions are detected and addressed different from pre-ignition events occurring during steady-state engine operating conditions.

Abstract: Provided is a control apparatus, which can successfully suppress that deterioration of combustion is caused in response to inflow of a large amount of blow-by gas to cylinders at the time of a valve return from a valve stop state in an internal combustion engine including a positive crankcase ventilation system and a variable valve operating mechanism that is capable of stopping at least one valve of an intake valve and exhaust valve in a closed state. A valve stop control is performed which stops the intake valve and exhaust valve in a closed state when a fuel cut of the internal combustion engine is executed. A deviation amount ?A/F between a predetermined target air fuel ratio and an actual air fuel ratio detected by an A/F sensor at the time of a valve return is obtained. A correction is performed to decrease a fuel injection amount by a fuel amount equivalent to the deviation amount ?A/F at the time of the subsequent valve returns.

Abstract: The control system has a structure in which sensor apparatuses each having a data communication function are connected to an electronic control apparatus through a common communication line, and the sensors of the sensor apparatuses are connected to the electronic control apparatus through separate individual signal lines to transmit sensor signals to the electronic control apparatus. The electronic control apparatus is configured to, prior to transmitting communication data to one of the sensor apparatuses through the communication line, set the signal line connected to the selected sensor apparatus in a state in which the voltage of the signal line is outside a variation range corresponding to a voltage range of the sensor signal, and set the signal lines connected to the other sensor apparatuses to each of which the communication data is not addressed in a state in which the voltage of the signal line is within the variation range.

Abstract: A control device in an IC engine estimates a future cylinder inside air quantity by delaying an operation of a throttle to make responsiveness of the IC engine and estimation precision of the cylinder inside air quantity compatible with each other. A delay time is provided in a calculation process until an instructed TA is outputted after a required KL is inputted. When calculation timing of a fuel injection quantity comes, an actual KL which is achieved in a time ahead by the delay time from the present time is estimated by using an air response model. When a read-ahead time of an intake valve exceeds the delay time, a change amount of the actual KL is estimated by using an air response model with a deviation between an estimated KL after td and a target KL set as a step input value.

Abstract: A controller performs compression self-ignition combustion control for combusting a mixture gas by injecting fuel into a cylinder in a negative valve overlapping period (NVO period), in which both of an exhaust valve and an intake valve are closed, and by causing self-ignition of the mixture gas using compression in a compression stroke. If knocking is detected during the above control, the controller performs knock suppression control for correcting a fuel injection quantity in the NVO period to suppress the knocking. If a pressure increase rate of cylinder pressure during the combustion is lower than a threshold value, the controller performs increase correction of the fuel injection quantity in the NVO period. If the pressure increase rate is equal to or higher than the threshold value, the controller performs decrease correction of the fuel injection quantity in the NVO period.

Abstract: A method of controlling fuel supplied to an engine is provided. In one example, a cylinder includes port and direct fuel injection. The method includes supplying a second fuel type from a second tank to the direct injector and supplying a first fuel type from a first tank to the port injector; and responsive to mis-fueling, supplying the first fuel type from the first tank to the direct injector. In response to receiving an indication of a mis-fuel, the direct fuel injector may be supplied with the second type of fuel from the second fuel storage tank. By supplying at least some fuel to the direct injector from a different source, fuel may be supplied to the DI fuel injector at various conditions to cool the DI fuel injector. In this way, overheating of the DI fuel injector may be reduced.

Abstract: There is provided with an ECU for estimating an unburned fuel amount (HC) emitted from an engine after fuel combustion or a temperature of a DPF based upon a required engine operating condition as a control target value. An exhaust gas temperature sensor for detecting a temperature of an exhaust gas emitted directly from the engine is provided. A program for compensating for an estimation error in regard to an estimation value of the unburned fuel amount estimated from the required engine operating condition, that is, an operating condition difference amount between the required engine operating condition and an actual engine operating condition, based upon an engine exhaust gas temperature detected from the exhaust gas temperature sensor is provided.

Abstract: Even when an engine is started in various combustion states, an excessive increase in engine speed at the start of the engine is suppressed without an influence of the combustion states and with an excellent responsiveness. Ignition timing (or a combustion injection amount) at the start of an internal combustion engine is corrected in accordance with a crank angle cycle ratio which is a ratio of a combustion period crank angle cycle and a reference crank angle cycle.

Abstract: A direct-injection internal combustion engine is fluidly coupled to a passive SCR system including a three-way catalytic converter upstream to an ammonia-selective catalytic reduction catalyst. Transition from an HCCI combustion mode to an SI combustion mode includes determining a preferred air/fuel ratio to achieve a minimum fuel consumption and maintain combustion stability at an acceptable level for a predetermined engine operating point during the SI combustion mode. A fuel injection timing, an engine spark timing and an engine valve lift are substantially immediately controlled from respective HCCI combustion mode settings to respective SI combustion mode settings. A transition to the preferred air/fuel ratio is coordinated with a transition of an engine valve phase from a respective HCCI combustion mode setting to a respective SI combustion mode phase setting.

Abstract: A cetane number detection device in which an angular velocity detection device (10) for detecting the rotation angular velocity of the crankshaft (11) of an engine (54), and which detects a variation in the value of the amplitude of the angular velocity detected by the angular velocity detection device (10) as a variation in cetane number.

Abstract: Systems and methods for controlling an internal combustion engine include adjusting fuel delivered to a cylinder during a transient event by an amount indexed by number of combustion events after detecting the transient event. A base fueling parameter may be adjusted by an adaptive correction value indexed by combustion events after the transient event is detected, with the adaptive value determined using air/fuel ratio difference of previous combustion events during similar transient operating conditions associated with the same combustion event index number. Ionization sensor signal characteristics may be used to determine actual air/fuel ratios used to determine the air/fuel ratio difference and corresponding adaptive correction values. The adaptive values may be modified in response to a vehicle refueling event based on an amount of added fuel relative to existing fuel in the vehicle fuel tank.

Abstract: A fuel injection control system for a motorcycle includes an ECU (Engine Control Unit) which calculates the amount of fuel to be injected by an injector based on data detected by various sensors. The fuel injection control system also includes a generator which supplies electric power to the injector and the ECU, and is driven in accordance with the engine, and a kick pedal for manually starting the engine by manually driving the generator with a user's foot. The ECU is configured to acquire data detected by the sensors at shorter intervals during a predetermined period before starting the engine than after the engine is started.

Abstract: A fuel injection control device includes a basic-injection-use map for deriving a basic injection amount and an additional-injection-use map for deriving an additional injection amount, each corresponding to the throttle opening. During operation of the engine, in each engine cycle, a first calculation stage for calculating the basic injection amount, and a second calculation stage provided after the first calculation stage are set. A first injection amount and a second injection amount obtained by applying the throttle opening measured in the first calculation stage and the second calculation stage, respectively, are compared. When the second injection amount is greater than the first injection amount, an additional injection amount is calculated by subtracting the first injection amount from the second injection amount; and when the first injection amount is greater than the second injection amount, the basic injection amount calculated in the first calculation stage is corrected.

Abstract: A method and system for estimating CO2 produced by an internal combustion engine disposed in a vehicle and transmitting the CO2 produced to a display device within the vehicle are disclosed. Estimated CO2 produced is based on amount of fuel consumed and fuel composition, e.g., alcohol content in a gasoline-alcohol blend. The amount of fuel consumed is computed based on fuel pulse width commanded to fuel injectors disposed in the engine, the pressure drop across the fuel injectors, and fuel injector nozzle cross-section. Instantaneous CO2 produced and/or average CO2 produced can be computed and displayed. Instantaneous CO2 produced is averaged over a short interval with the display updated regularly. Average CO2 produced is averaged over a typically longer interval, being reset, in one embodiment, by an operator of the vehicle depressing a reset button.

Abstract: A mixed-mode method for operating a vehicle's propulsion plant to travel at a selected average speed using the minimum amount of fuel. The method involves travelling in one mode at high speed part of the time, and in a different mode at low speed part of the time, in such a way that the average speed is the selected value.

Abstract: A method and system for igniting a lean fuel mixture in a main chamber of an internal combustion engine by igniting a rich air-fuel mixture in a pre-combustion chamber which is fuelled using a controlled valve. For a stable and consistent ignition of the main chamber and simultaneous reduction of emission of the internal combustion engine, a closed loop control adjusts the fuel amount and the fuelling time for the pre-combustion chamber in order to achieve a light off in an optimal time window and by sufficient ignition energy.

Abstract: A method of operating a hybrid vehicle propulsion system includes selectively operating the engine to consume fuel stored on-board the vehicle based on a residence time of the fuel stored on-board the vehicle and further based on a profile of ambient conditions over the residence time.

Abstract: A method for operating an exhaust gas mass flow sensor which is used, in particular, in exhaust gas mass flows of motor vehicles has an operating mode and a cleaning mode. In an operating mode, the exhaust gas mass flow sensor is operated at an operating temperature. In a cleaning mode, the exhaust gas mass flow sensor is changed over for the purpose of cleaning a measurement region and is cleaned at a cleaning temperature which is higher than the operating temperature.

Abstract: The present invention has an object to make abnormal combustion of an internal combustion engine detectable by simple means at low cost. For this purpose, an abnormal combustion detecting device provided by the present invention uses a direct injection injector as means for detecting abnormal combustion. In the direct injection injector relating to the abnormal combustion detecting device, a sack chamber is provided at a tip end of a nozzle body, and a nozzle hole is formed to cause the sack chamber and a combustion chamber to communicate with each other. A needle is housed inside the nozzle body, and the sack chamber is opened and closed by the needle, whereby a fuel is directly injected into the combustion chamber.

Abstract: A control apparatus for an internal combustion engine includes: a fuel property sensor which is provided between a fuel tank and a delivery pipe and which detects a component ratio of fuel; a fuel property value calculator that calculates an injector fuel property value for each cylinder using the component ratio detected by the fuel property sensor a period of time ago, which is equal to an amount of time required for the fuel to travel from the fuel property sensor to each fuel injector, as a value corresponding to the present component ratio of the fuel near the corresponding injector; and an engine-restart-time fuel injection amount calculator that calculates a fuel injection amount for each cylinder based on an engine-off duration in a case where the internal combustion engine is restarted after the internal combustion engine is stopped when the injector fuel property value varies from cylinder to cylinder.

Abstract: An engine system includes: a mixture portion capable of mixing a first liquid as a main fuel with a second liquid at a predetermined mixture ratio; an engine to which a mixed fuel produced by mixing the first liquid with the second liquid is fed from the mixture portion; and a control portion controlling the mixture ratio of the mixed fuel to be a target mixture ratio based on a driving state of the engine. The control portion controls the target mixture ratio based on a feeding period from the time when the mixed fuel is fed from the mixture portion to the time when the mixed fuel arrives at the engine.

Abstract: A control system (and a method of operating the system for an internal combustion engine. The control system has a trigger circuit for supplying trigger signals and an output stage having a plurality of output channels which supply actuating signals. The trigger circuit and the output stage are connected to one another by a selection interface and a trigger interface that is a single control line which supplies a time control signal.

Abstract: An intake air control apparatus for an internal-combustion engine includes an intake air adjusting device. An operating mode determination device is configured to determine whether the internal-combustion engine is in a predetermined high rotation speed and high load operation mode in which cooling is required by increasing an amount of fuel. An intake air reduction controller is configured to, if the operating mode determination device determines that the internal-combustion engine is in the predetermined high rotation speed and high load operation mode, control the intake air adjusting device so that an intake air amount is reduced in accordance with a rotation speed of the internal-combustion engine and an ignition timing in order to restrict a fuel injection quantity to be injected from a fuel injection valve so that the fuel injection quantity does not exceed a maximum fueling rate of the fuel injection valve.

Abstract: There is provided an air-fuel ratio control device comprising: fuel supply means; engine operation state detection means; air-fuel ratio information detection means; and an electronic control unit, the electronic control unit being configured to determine a fuel injection amount which realizes a target air-fuel ratio while using engine load information by the engine operation state detection means on the basis of air-fuel ratio information by the air-fuel ratio information detection means, and then output a driving signal to the fuel supply means, to execute feedback control mainly at an excessively rich side air-fuel ratio, characterized in that the air-fuel ratio information detection means is an exhaust gas temperature sensor, and while estimating an air-fuel ratio at this time on the basis of detected exhaust gas temperature information by a predetermined obtaining method, the air-fuel ratio is used for the control.

Abstract: Engine surge includes oscillations in engine torque resulting in bucking or jerking motion of a vehicle that may degrade driver experience. The present application relates to increasing reformate entering an example engine cylinder in response to engine surge.

Abstract: Methods and systems are described for conserving fuel used by an engine. In some embodiments a control module processes a user-provided input, as a first function, into a second function. The second function can be used to direct the engine with a directive output power. The directive output power may have regions equal to, greater than, and/or less than what the power output would be if the engine were controlled using the user-provided input.

Abstract: A method for determining the quality of the fuel for an internal combustion engine, in particular a direct-injection internal combustion engine in a vehicle, which is characterized by the following be performed: the internal combustion engine is operated in idle mode under predefinable operating conditions, the curve of the injection quantity, necessary for idling, over the engine temperature is determined, and the fuel quality is inferred from the curve of the injection quantity over the engine temperature.

Abstract: When an engine driving condition has been changed from an idling condition to a vehicle running condition, a controller measures an idling period. When the idling period is longer than a determination time period immediately after the vehicle is started, a penetrating-force-decrease control is performed. Therefore, even when a piston temperature is relatively low and particulate matters are easily generated, it can be restricted that fuel adheres to the piston top-surface by performing the penetrating-force-decrease control. Further, in the penetrating-force-decrease control, since the fuel is injected at optimum injection timing, it can be avoided that emission and fuel economy are deteriorated.

Abstract: In a method for controlling an internal combustion engine, in particular a diesel internal combustion engine, at least one variable is formed on a cylinder-specific basis, which variable characterizes a respective profile of a combustion in an associated combustion chamber, and the control of cylinder-specific fuel injection parameters is influenced as a function of said at least one variable which characterizes the combustion profile.

Abstract: The method comprises receiving from the vehicle controller, values associated with the engine speed and of another parameter indicative of the engine operating conditions, such as the total fuelling amount, and controlling the fuel injection parameters according to the engine state, which, for example, can include a normal operation mode, a filter regeneration mode, an engine protection mode, high or low transient load modes, and operating at different altitudes, through algorithms implemented in an electronic controller.

Abstract: The invention relates to a method for reducing uncontrolled combustions in an internal combustion engine, which occur independently of the ignition by a spark plug, wherein uncontrolled combustions are detected in the internal combustion engine (1). In order to reduce the damaging effects of the uncontrolled combustions to the internal combustion engine, the incipient uncontrolled combustion (B) is reduced after said incipient uncontrolled combustion (B) has been detected.

Abstract: Various engine control parts, which are actually attached to the engine and are necessary for engine control, are constructed in a state where electrical transmission and fuel supply are enabled in a manner similar to a case where the engine control parts are mounted on an actual engine, and model-based control is performed using numerical formulas on the same conditions as those of the actual engine on the basis of test data of the actual engine written in an electronic control unit constituting one of the engine control parts.

Abstract: The invention provides a method for preferably controlling an internal combustion engine by precisely estimating a current value of a temperature of an exhaust device of an internal combustion engine provided with a variable valve, an exhaust turbo supercharger and the like, and controlling an affector of a temperature of an exhaust gas on the basis of a difference between a reference value of the exhaust device temperature and the current value of the exhaust device temperature.

Abstract: The present invention relates to a fuel supply control device for an internal combustion engine and a fuel vapor processing method. In the fuel supply control device that calculates a manipulated variable of a fuel pump such that a fuel pressure detected by a fuel pressure sensor is brought close to a target fuel pressure, a determination whether a fuel vapor is generated is made based on a detection value of the fuel pressure and the manipulated variable in a fuel pump, or the determination is made based on an amplitude of the detection value of the fuel pressure and an average fuel pressure in a fuel supply piping. During the fuel vapor generation, the target fuel pressure is corrected to be a higher value to increase the fuel pressure, thereby compressing and removing the fuel vapor. Therefore, in a fuel supply system, the fuel vapor generation can be detected at low cost to suppress the fuel vapor generation.

Abstract: In a method for controlling a fuel injection system of an internal combustion engine with at least one combustion chamber, wherein the fuel injection system comprises a high pressure pump, whose flow rate is controllable, a control parameter of the high pressure pump is evaluated during the operation of the internal combustion engine. Said control parameter makes a detection of a bottleneck with the high pressure pump with respect to fuel quantity possible.

Abstract: A method for operating an internal combustion engine (10) for a motor vehicle, said internal combustion engine (10) comprising an exhaust gas system (26) having at least one catalytic converter (28; 30) and at least one lambda probe (38; 40). The internal combustion engine (10) is operated alternately with a lean and a rich fuel-air mixture after a cold start for heating the catalytic converter (28; 30). The lambda probe (40) is heated after the cold start in such a way that it is ready for operation after at most 10 s and the internal combustion engine (10) is operated with a two-level control based on a signal (UL) from the lambda probe (40), such that the change between the operation with lean fuel-air mixture and the operation with rich fuel-air mixture is in each case initiated by the signal (UL) from the lambda probe (40).

Abstract: A control system for an engine capable of operating on more than one type of fuel includes an engine control unit that determines a default fuel volume to be injected into the engine based on relevant engine parameters and characteristics of a default fuel type. A default mass fuel flow rate is derived from the default fuel volume and relevant engine parameters. The actual mass fuel flow rate into the engine is inferred from the mass air flow rate into the engine and the exhaust gas air-to-fuel ratio, which is determined using a wide range oxygen sensor. A fuel correction factor is calculated from the default mass fuel flow rate and the inferred mass fuel flow rate. The fuel correction factor is used to increment or decrement the default fuel volume in a subsequent fuel injection cycle thereby incrementing or decrementing the inferred mass fuel flow rate toward the default mass fuel flow rate.

Abstract: A common rail type fuel injection system of an engine includes: a common rail for accumulating and holding high-pressure fuel; a fuel pump for pressure-feeding fuel to the common rail; and an injector for injecting the high-pressure fuel accumulated and held in the common rail. A pressure sensor is disposed in a fuel suction port of the injector. An ECU sequentially detects a fuel pressure varied when the injector injects the fuel and sequentially detects a fuel pressure varied when the fuel pump pressure-feeds the fuel. When the injector injects the fuel, the ECU computes injection pressure by the detection values of these pressures and computes injection characteristics by the injector on the basis of the injection pressure.

Abstract: The internal-combustion-engine ignition diagnosis apparatus is configured in such a way that the first duration setting unit sets the first detection duration in a predetermined duration including a time instant when the spark discharge is generated, the second duration setting unit sets the second detection duration after the first detection duration, the diagnosis unit determines normality of the spark discharge, based on a signal state in the second detection duration, and regardless of the signal state in the second detection duration, determines abnormality of the spark discharge, based on a signal state in the first detection duration.

Abstract: In an exhaust emission purifying apparatus for reductively purifying NOx in the exhaust emission by using a liquid reducing agent or its precursor, to be referred to as “liquid reducing agent” herein, a dosing flow rate of the liquid reducing agent according to engine operating conditions is computed, and the dosing of the liquid reducing agent is controlled based on the computed dosing flow rate, and also, it is judged whether or not a supply system of the liquid reducing agent is failed, based on a ratio between an integrated amount obtained by sequentially integrating the dosing flow rate and a consumed amount of the liquid reducing agent.

Abstract: A fuel injection controller (incorporated in an engine control ECU) for controlling an injection operation of an injector has a program for executing injections in plural injection patterns including an injection pattern of a multiple injection in a certain order into a certain cylinder of the engine during non-injection operation and a program for obtaining sums of fluctuation degrees of an engine operating condition due to all the injections in a first injection unit composed of one (single stage injection) of the plural patterns and all the injections in a second injection unit composed of a different one (multiple injection of two stages) of the plural patterns which are executed by the former program, with an injection condition (cylinder number and data number N).

Abstract: A control system includes an engine control module that generates fuel injector command signals for fuel injectors of an engine and engine parameter signals that indicate operating characteristics of the engine. A fuel injector control module communicates with the engine control module via a network. The engine control module transmits the engine parameter signals to the fuel injector control module via the network. The fuel injector control module generates compensated fuel injector signals based on the fuel injector command signals and the engine parameter signals. The engine control module may generate fuel injector command signals for a gaseous fuel mode based on signals received from the fuel injector control module.

Abstract: In an apparatus for controlling an air/fuel ratio of a general-purpose internal combustion engine using mixed fuel containing alcohol and gasoline and operated at a desired engine speed inputted by the operator while a throttle opening is regulated such that a detected engine speed converges to the inputted desired engine speed, a fuel injection amount for mixed fuel determined based on fuel injection amount characteristics is increased/decreased when a load is kept constant and the output air/fuel ratio (at which an output of the engine becomes maximum) is estimated. And the fuel injection amount is corrected based on the estimated air/fuel ratio, thereby enabling to estimate the output air/fuel ratio without using an expensive air/fuel ratio sensor and to feedback-control the fuel injection amount such that the engine is operated at the output air/fuel ratio.