Abstract: A method of operating an internal combustion engine having an; electromagnetically driven intake valves for a vehicle. With the method, deviation of an opening operation of the electromagnetically driven intake valve in response to a command signal for opening the intake valve from a predetermined characteristic is detected, and at least one of parameters used for controlling operation of the internal combustion engine is corrected so as to reduce a change in an intake air charging state in which the internal combustion engine is charge with the intake air. A valve closing timing of the intake valve or a valve closing timing of the exhaust valve that cooperates with the intake valve may be used as parameters to be corrected.

Abstract: A system and method for utilizing a humidity sensor with an internal combustion engine of a vehicle is described. Specifically, information from the humidity sensor is used to adjust a desired air-fuel ratio to reduce engine misfire while improving vehicle fuel economy. Further, such information is also used to adjust timing and/or lift of the valve in the engine cylinder. Finally, diagnostic routines are also described.

Abstract: A system for actuating sequential engine function transducers such as fuel injector solenoids comprising a plurality of switch nodes equal in number to the number of cylinders of the engine. Each switch node includes a high current switch such as a transistor and an individually addressable driver circuit for causing the transistor to conduct when an address unique to the driver is received. The nodes are preferably disposed in close physical proximity to the injector solenoids. Low current address carrying lines are connected between the address generator and the individual switch drivers to activate them in sequence. Only a single high voltage high current supply line need be provided. The transducers may also be intake and/or exhaust valve actuators or spark ignition devices.

Abstract: In variable valve control system and method for a vehicular multi-cylinder internal combustion engine, a first learning timing at which a reference position of a lift characteristic is learned for a first cylinder group is deviated from a second learning timing at which the reference position is learned for a second cylinder group.

Abstract: An apparatus and method of controlling an engine by determining the state of an ignition command device and the speed of an engine and operating a fuel pump during a predetermined period in response to the ignition command device being in a predetermined state and the speed being substantially zero.

Abstract: Disclosed herein are methods of cranking and/or operating an engine that eliminates the need for use of a cam sensor. The methods implemented with internal combustion engine comprising a plurality of cylinders whose firing sequence occurs over two revolutions of a crankshaft with a first set of cylinders comprising a power stroke during the first crankshaft revolution and a second set of cylinders comprising the power stroke of a second crankshaft revolution. The methods involve manipulating fuel injection command signals to occur out of their proper sequence, monitoring and engine indicator responsive to firing and non-firing of cylinders, and identifying correct engine phase based on fluctuations in the engine indicator. Also disclosed herein are software product embodiments comprising program code modules that cause a engine control unit to manipulate the generation of fuel injection command signals to take place outside their correct sequence.

Abstract: In a combustion control system of an engine employing an exhaust purifying device, a control unit determines, based on an operating condition of the exhaust purifying device, whether a request for an exhaust temperature rise is present. The control unit executes, by way of fuel injection control in presence of the request of the exhaust temperature rise, a split retard combustion mode in which a main combustion needed to produce a main engine torque and at least one preliminary combustion occurring prior to the main combustion are both achieved, and the preliminary combustion occurs near top dead center on a compression stroke, and the main combustion initiates after completion of the preliminary combustion. The control unit executes a fail-safe process that an injection timing of main fuel injection is phase-advanced, when a predicted temperature value of the exhaust purifying device exceeds a predetermined threshold value.

Abstract: An internal combustion engine includes an engine body including a cylinder that defines a combustion chamber, an intake opening that faces the combustion chamber, and an intake passage in communication with the combustion chamber through the intake opening, a piston provided in the cylinder, an intake valve that opens and closes the intake opening, a throttle valve provided in the intake passage, and an injector that injects fuel between the throttle valve in the intake passage and the intake opening. A ratio of a volume of the portion that extends from the throttle valve in the intake passage to the intake opening, to a stroke volume of the cylinder is at most approximately 0.61. The time period in which fuel injection from the injector is terminated during an idling operation is set within a period of time after one intake stroke has been completed and before the next intake stroke is begun.

Abstract: An electronic control unit for an internal combustion engine having a fuel injection system and an ignition system including: timing determination means (2) for determining timing sequences for injection events of the fuel injection system and ignition events of the ignition system and to provide update timing sequence data (10) to a schedule sequencing means (3) adapted to control at least one driver circuit (4) wherein the at least one driver circuit (4) is adapted to provide drive pulses (11) to the fuel injection system and ignition system; wherein the schedule sequencing means (3) is adapted to select between update sequence data to at least one of an injection of ignition event, such that the update timing sequence data is selected when there is no current injection occurring.

Abstract: In an internal combustion engine, which is provided with a variable valve mechanism that varies an open/close characteristic of an intake valve, a target open/close characteristic of the intake valve is determined. Simultaneously, a control speed at a time when the intake valve is controlled to have the target open/close characteristic is determined. As a result, the variable valve mechanism is controlled according to the target open/close characteristic and the control speed.

Abstract: A learning apparatus for a variable valve control of an internal combustion engine includes a variable valve operating mechanism, an actuator that rotationally drives the control shaft, a control shaft sensor that detects an angular position of the control shaft, a reference position determining section that determines whether or not the control shaft has reached a predetermined reference position under the drive from the actuator, a learning section that learns an output value of the control shaft sensor when it is determined that the control shaft has reached the reference position and stores the learned output value as a sensor output reference value, and a learning preparing section that causes the control shaft to be driven by the actuator toward the reference position when a crankshaft of the engine is rotating and supply of fuel to the engine is stopped. A learning method is also provided.

Abstract: A method of regulating or controlling a cyclically operating internal combustion engine using a computation model by which the cycle or portions of the cycle of the internal combustion engine is, or are, divided into individual parts and the operating condition within each cycle part is determined using measured values, stored and/or applied data in order to obtain actuating variables for operating the internal combustion engine. The time limits of the cycle parts are at least partially calculated as a function of at least one variable engine operating parameter. The operating status of an internal combustion engine can thus be determined readily and quickly while still with sufficient accuracy so as to obtain actuating variables suited for regulating or controlling the internal combustion engine using electronic control units available for series operation.

Abstract: A fuel injection system includes an injector, a controller, and a cylinder internal pressure sensor. The injector injects fuel to an engine. The controller controls injection start timing of the injector, an injection amount, and a supply pressure of the injected fuel. The cylinder internal pressure sensor detects one of a cylinder internal pressure and a heat release rate of the internal combustion engine. The controller has a standard estimator and a corrector. The standard state estimator obtains a standard state of one of the cylinder internal pressure and the heat release rate upon fuel injection from the injector. The corrector corrects at least one of the injection start timing, the injection amount, and the supply pressure in a direction to eliminate a difference that exists between the standard state obtained by the standard state estimator and one of the cylinder internal pressure and the heat release rate detected by the cylinder internal pressure sensor.

Abstract: Either associated process control or discrete process control is selected for valve timing control according to the engine operation state. Under the associated process control, the target displacement angle INP of an intake camshaft (22) is computed according to the engine operation state, and the actual displacement angle INR of the camshaft (22) is brought closer to it. Further, based on the target valve overlap amount OVP computed according to the engine operation state and the actual displacement angle INR, the target displacement angle EXP of an exhaust camshaft (23) is computed, and the actual displacement angle EXR of the camshaft (23) is brought closer to it. Under the discrete process control, the target displacement angles INP, EXP are computed according to the engine operation state, and the actual displacement angles INR, EXR are brought closer to them.

Abstract: A method and apparatus for determining a parameter associated with a delivery of fuel in an engine. The method and apparatus includes determining an initial parameter value associated with the delivery of fuel, determining at least one compensation factor based on a heating effect of a fuel and a fuel system, and applying the at least one compensation factor to the initial parameter value to derive a compensated parameter value.

Abstract: The present method and apparatus employ a signal indicative of cylinder pressure within the combustion chamber of an internal combustion engine to control combustion phasing or start of combustion (SOC) in subsequent cycles of the engine where the engine is driven by combustion of both a fuel/air premixed charge and a directly injected quantity of fuel. A ratio of signals indicative of pre-combustion pressure and post-combustion pressure within a cycle are employed to estimate SOC and then, based on a predetermined target SOC, an ignition lever is employed to adjust subsequent SOC. A preferred ignition lever is, in a pilot fuel ignited engine, pilot fuel quantity.

Abstract: Having the ability to quickly and easily test whether a variable valve mechanism is operating properly can avoid unnecessary down time and the expense associated with potentially replacing a good component on an internal combustion engine. A test can include inducing a misfire in a cylinder of the engine at least in part by commanding a change to a state of a variable valve mechanism at a predetermined timing. For instance, in the case of a diesel engine, a variable valve mechanism can be tested by closing an intake valve late so as to reduce a cylinder compression ratio to a point that autoignition of fuel does not occur, resulting in a misfire. If a misfire is detected, either audibly by a person or possibly electronically via a sensor, then proper activation of the variable valve mechanism is confirmed.

Abstract: In an internal combustion engine provided with a variable valve mechanism that variably controls at least an operating characteristic (valve lift amount and the like) of an intake valve, a valve opening area AWm at a valve overlap time is calculated based on a valve lift amount (VCS-ANGL) and opening timing IVO of the intake valve, and a spit-back gas amount Wm at the valve overlap time is calculated based on the valve opening area AWm. On the other hand, a volume flow ratio (basic actual engine volume flow ratio) RQH0VEL1 in the intake valve, equivalent to an actual intake air amount of the engine, is calculated based on the valve lift amount and closing timing of the intake valve, and a basic residual gas amount Wcyl is calculated based on the basic actual engine volume flow ratio RQH0VEL1. Then, a resultant obtained by adding the spit-back gas amount Wm and the basic residual gas amount Wcyl, is set as a total residual gas amount of the engine.

Abstract: By a lean burn operation, a highly efficient operation region is enlarged, the proportion of engine operation in a low torque condition is increased, and the proportion of motor operation using a battery is decreased. It is possible to provide a hybrid car of an engine-electric motor configuration which can effect a highly efficient operation without increasing the capacity of motor and that of battery.

Abstract: In an internal combustion engine provided with a variable valve mechanism that varies an open/close characteristic of an intake valve, a target open/close characteristic of the intake valve is determined and at the same time, a control speed of when the intake valve is controlled to have the target open/close characteristic is determined, so that the variable valve mechanism is controlled according to the target open/close characteristic and the control speed.

Abstract: A microcomputer calculates a requisite time for controlling a predetermined device of an internal combustion engine. The microcomputer estimates time required for a crank shaft of the engine to rotate from a present crank angle to a designated crank angle. The microcomputer predicts a relationship between times required for the crank shaft to rotate consecutive angular regions positioned before and after the present crank angle based on measurement result with respect to times required for the crank shaft to rotate consecutive angular regions positioned before and after a preceding crank angle advanced a predetermined amount from the present crank angle.

Abstract: A method and system to control engine shutdown in a hybrid electric vehicle (HEV) are provided. Tailpipe emissions are reduced during the many engine shutdowns and subsequent restarts during the course of an HEV drive cycle, and evaporative emissions are reduced during an HEV “soak” (inactive) period. The engine shutdown routine can ramp off fuel injectors, control engine torque (via electronic throttle control), control engine speed, stop spark delivery by disabling the ignition system, stop purge vapor flow by closing a vapor management valve (VMV), stop exhaust gas recirculation (EGR) flow by closing an EGR valve, and flush the intake manifold of residual fuel (vapor and puddles) into the combustion chamber to be combusted. The resulting exhaust gas byproducts are then converted in the catalytic converter.

Abstract: An allocation map stored in a ROM in an ECU is set corresponding to the kinds of fuel injection valves. Therefore, at the time of incorporating fuel injection valves into a diesel engine, it is possible to freely set how injection correction amount data read from a two-dimensional code by a writing device is allocated in an injection correction amount map in steps S214 and S216, separately for the individual kinds of fuel injection valves. Since the injection correction amount map in which the injection correction amount data is arranged with a distribution of density corresponding to the kinds of fuel injection valves, it is possible to change and set correction points with high degree of freedom even though the amount of data recordable in the two-dimensional code is limited. Therefore, high-precision data maps can be used separately for the individual kinds of fuel injection valves.

Abstract: A fuel injection timing control system and method is provided including steps of: determining a base fuel injection timing, calculating a reference boost pressure based on a current engine operating condition, calculating a fuel injection timing compensation value based on a difference between the calculated reference boost pressure and a current boost pressure, and calculating a final fuel injection timing by compensating the base fuel injection timing with the fuel injection timing compensation value.

Abstract: A spark ignition engine (2) has a fuel injector (8) in an intake port (7). An engine rotation speed sensor (9) detects the rotation speed of the engine (2). The controller (1) determines the target fuel injection amount of the fuel injector (8) during startup of the engine (2) by correcting the basic injection amount in response to the trend in the variation in the engine rotation speed. When the rotation speed of the engine (2) decreases, the controller (1) sets the target fuel injection amount to be smaller than when the rotation speed of the engine (2) is increasing at an identical rotation speed. As a result, effects on the air-fuel ratio related to wall flow relative to fluctuations in the rotation speed of the engine (2) are eliminated and the control accuracy of the air-fuel ratio of the engine (2) is improved.

Abstract: A method that provides increased flexibility to measure dynamic range of a rotating system is provided. The method includes the steps of: providing a first rotating member; providing a second rotating member suitably engaged to the first rotating member; providing a set of sensors disposed to sense variations in characteristics along a circumference of the first member and the second member respectively; providing a controller for receiving information sensed by the sensors; determining a rate of rotation of the rotating members; selectively using the sensed information thereby at different rate of rotation different amount of the sensed information is used.

Abstract: The present invention provides a fuel injection quantity control device for a diesel engine, having injection quantity determination unit for determining the required fuel injection quantity based on the accelerator opening degree and engine revolution speed. The device comprising control unit for conducting a minimum cut-off control. With the present invention, the generation of white smoke during injection restart following the fuel injection cut-off can be prevented merely by controlling the injection quantity, without using a separate device.

Abstract: A control apparatus for a motor vehicle is provided in which each of a plurality of output values of the vehicle varies depending upon a plurality of input control parameters for controlling the vehicle. The control apparatus changes the input control parameter or parameters so that each of the output values becomes substantially equal to a corresponding target output value. The control apparatus then determines adapted values of the input control parameters, based on values of the input control parameters obtained when each of the output values becomes substantially equal to the corresponding target output value or falls within a permissible adaptation range of the target output value.

Abstract: The present invention is constructed such that there is provided a variable valve opening mechanism which varies an opening of an engine valve continuously, the opening of the engine valve is feedback controlled to a target opening and at the same time, at least the opening of the engine valve relative to controlled variable of a first reference opening is detected to be learned at an initial time, and after the initial learning, the opening of the engine valve relative to controlled variable of a second reference opening different from the first reference opening is detected to be learned, and based on the initial learning result and a newest learning result of the second reference opening, an opening detection characteristic of an opening sensor is learned.

Abstract: A system and method for utilizing a humidity sensor with an internal combustion engine of a vehicle is described. Specifically, information from the humidity sensor is used to adjust a desired air-fuel ratio to reduce engine misfire while improving vehicle fuel economy. Further, such information is also used to adjust timing and/or lift of the valve in the engine cylinder. Finally, diagnostic routines are also described.

Abstract: A method and system for indirectly estimating ambient air temperature. The ambient air temperature is estimated based on filtering a temperature input from a turbocharger air inlet sensor. The filtering includes compensating for engine compartment temperature variations which vary relative to the actual ambient temperature.

Abstract: A fuel injection control device in which fuel injected into the combustion chamber is ignited after a pre-mixing period has elapsed following the completion of the injection of the fuel, includes target pre-mixing period determining unit for determining the target pre-mixing period on the basis of the engine operating conditions, actual pre-mixing period detection unit for detecting the actual pre-mixing period, and pre-mixing period adjustment means for adjusting the pre-mixing period of the fuel so that the actual pre-mixing period approaches the target pre-mixing period. With this device, the pre-mixing period of the fuel can be appropriately controlled, and the exhaust gas can be reliably improved.

Abstract: An internal combustion engine (10), especially of a motor vehicle, is operated with a method wherein the fuel is injected directly into a combustion chamber (12) of the internal combustion engine (10) with at least one injection (36) per work cycle. In order to reduce the fuel consumption and to improve the emission performance of the internal combustion engine (10), it is suggested that a fuel injection (36) includes a plurality of short injection pulses (32) spaced in time from each other.

Abstract: A system and a method for correcting the injection characteristics of at least one injector, having a device for storing information and an arrangement for controlling the at least one injector, taking into account the stored information. The information may be ascertained by comparing setpoint values to actual values individually at a plurality of test points of at least one injector, and may be specific.

Abstract: In a method of controlling an internal combustion engine, at least one operating variable is controlled, a pre-control ignition timing efficiency is formed as a function of operating parameters of the engine and/or external intervention measures, and the pre-control ignition timing efficiency determines the setpoint values of the at least one operating variable. In a transition from a first operating state to a second operating state, the pre-control ignition timing efficiency is varied by a transition function.

Abstract: The invention relates to a method for operating an internal combustion engine (1) especially of a motor vehicle, wherein fuel, which is to be injected into a combustion chamber (4) or into an intake manifold (7) of the engine (1), is present in a pressure store (13) at a variable injection pressure (p). The injection pressure (p) in the pressure store (13) is adjusted in dependence upon the temperature (T) of the engine (1) in order to obtain an optimal operation of the engine (1) with respect to the lowest possible consumption of fuel and a lowest possible exhaust-gas emission in specific operating states of the engine (1), for example, after a cold start or during a warm-up phase. Preferably, the injection pressure (p) is increased at a temperature (T) of the engine (1) below the operating temperature thereof. In addition, the injection time point can be adjusted to later time points at low temperatures (T) of the engine (1).

Abstract: A method and system may be provided to perform a process for controlling NOx emissions of an target engine. In one embodiment of the invention, the process may include determining predicted NOx values based on a model reflecting a predetermined relationship between control parameters and NOx emissions, wherein the control parameters include ambient humidity, manifold pressure, manifold temperature, fuel rate, and engine speed associated with the engine. Further, the process may include adjusting the model based on a determination of whether the predicted NOx values meet a predetermined criteria associated with actual NOx values. The adjusted model may be stored in a memory associated with the engine whereby NOx emissions exhausted from the engine may be reduced based on virtual NOx emission values determined from the adjusted model.

Abstract: In response to start of cranking in an internal combustion engine by a starter, a fuel injection control starts. When an initial combustion of the fuel injected into the internal combustion engine is detected based on a rotational speed of a crankshaft, it is determined that the internal combustion engine in a warm-up period, and a control for reducing a fuel injection period is executed. When it is detected that the rotational speed of the crankshaft exceeds a predetermined rotational speed, it is determined that the internal combustion engine is in a start-up promotion period, and a control for extending the fuel injection period is executed.

Abstract: A main CPU determines whether or not there is a request for one valve driving based on an engine operating state such as an engine speed and a load factor, with reference to a control map. When it is determined that there is a request for one valve driving, it is determined whether or not there is an overlapping period between opening periods. When it is determined that there is no overlapping period, a high speed control is performed for controlling electromagnetically driven valves. When it is determined that there is no request for one valve driving, or when it is determined that there is the overlapping period, a low speed control is performed for controlling electromagnetically driven valves.

Abstract: A method and a device for controlling an internal combustion engine having a central control unit and a peripheral control unit are described. The central control unit transmits request signals to the peripheral control unit. At least two load circuits receive control signals from the peripheral control unit. The peripheral control unit checks the request signals and/or additional signals for plausibility.

Abstract: A method for processing an accelerometer data set generated from an operating internal combustion engine is disclosed. The processed accelerometer data is cepstrally filtered and a heat release trace is pulled from the accelerometer data set. That heat release trace is then used to estimate combustion quality and combustion phasing within the engine and control future combustion events using this information. Misfire and knock sensing is also incorporated into the engine controls. The method provides controls for an engine to allow it to adjust combustion from cycle window to cycle window generally without the need for expensive and less durable direct pressure measurement devices as compared to accelerometers. The resulting fuel injection speed results in the fuel passing through shock waves within the combustion chamber, which, in turn, promotes combustion of the fuel by promoting mixing of the fuel and intake charge within the combustion chamber.

Abstract: A hardware system is provided for performing angle-to-time and time-to-angle conversions in a dynamic angular measurement and control system. The system has the capability of updating scheduled event times of other hardware timers in the system that are being used to generate output events at some specific angular position in the future. One application of the system is in automotive powertrain control systems in which the position of the engine is determined from a pulsed signal generated by a rotating crankshaft that accelerates and decelerates over time. The system performs critical calculations in hardware which consumes less CPU bandwidth than existing systems, resulting in potential cost savings for the overall system.

Abstract: In a method of controlling a diesel engine that performs an injected fuel quantity reduction process for preventing black smoke based on an engine speed, and performs an injected fuel quantity reduction process for preventing shift shock during shifting of an automatic transmission, the injected fuel quantity reduction process for preventing black smoke is inhibited or the amount of reduction of the injected fuel quantity for preventing black smoke is reduced during shifting of the automatic transmission or during execution of the injected fuel quantity reduction process for preventing shift shock.

Abstract: A method and apparatus for determining a parameter associated with a delivery of fuel in an engine. The method and apparatus includes determining an initial parameter value associated with the delivery of fuel, determining at least one compensation factor based on a heating effect of a fuel and a fuel system, and applying the at least one compensation factor to the initial parameter value to derive a compensated parameter value.

Abstract: The invention relates to a method for controlling an internal combustion engine with a fuel injection system which can comprise, in addition to a main injection quantity, an additional amount of pre-injected and/or post-injected fuel for each injection pulse for each combustion chamber for each combustion cycle at a given injection time. A theoretical torque is determined from an accelerator pedal value, rotational speed and air or fuel mass flow while taking into account a factor from a family of characteristics. According to the invention, the calculated theoretical torque is corrected in the case of a pre-injected or post-injected fuel mass flow by taking into account, in a correction factor, a value for a time or phase difference of the amount of pre-injected or post-injected fuel and the main injection quantity for each cycle.

Abstract: Method and apparatus for controlling the ration of the amount of fuel and the amount of air in a natural gas fueled internal-combustion engine intended to work in a specified engine-specific load-rotation speed diagram. The apparatus includes a throttle for controlling the amount of air supplied to the combustion chamber in the internal-combustion engine, injection devices for controlling the amount of natural gas supplied to the combustion chamber and control devices for controlling the throttle and the injection devices, whereby the control devices are arranged to control the ratio of the amount of fuel and the amount of air dependent on the current operating point in the internal-combustion engine's load-rotation speed diagram.

Abstract: An engine has cylinders, a fuel injection unit with a valve operable in response to a valve control signal to cause fuel to be injected into the cylinders, and a control unit which generates the valve control signal. A method of controlling the valve includes sensing a time associated with movement of the valve corresponding to start of a fuel injection event, and modifying the valve control signal as a function of the sensed time. The method further includes determining a rise time of the valve control signal, determining a valve operation delay time as a function of the rise time, determining a difference time representing a difference between a desired valve operation time and the sensed time, comparing the valve operation delay time to the difference time, and adjusting timing of the valve control signal as a function of the comparison.

Abstract: A method and system to control engine shutdown for a hybrid electric vehicle (HEV) is provided. Tailpipe emissions are reduced during the many engine shutdowns and subsequent restarts during the course of an HEV drive cycle, and evaporative emissions are reduced during an HEV “soak” (inactive) period. The engine shutdown routine can ramp off fuel injectors, control engine torque (via electronic throttle control), control engine speed, stop spark delivery by disabling the ignition system, stop purge vapor flow by closing a vapor management valve (VMV), stop exhaust gas recirculation (EGR) flow by closing an EGR valve, and flush the intake manifold of residual fuel (vapor and puddles) into the combustion chamber to be combusted chamber to be combusted. The resulting exhaust gas byproducts are then converted in the catalytic converter.

Abstract: The present invention provides a fuel injection quantity control device for a diesel engine, having injection quantity determination unit for determining the required fuel injection quantity based on the accelerator opening degree and engine revolution speed. The device comprising control unit for conducting a minimum cut-off control such that, at the time the injection is to be restarted after the fuel injection has been cut-off for the predetermined time, the fuel injection cut-off is continued when the required injection quantity determined by the unit is less than the prescribed injection quantity Qmin, and the fuel injection is restarted when the required injection quantity is equal to the prescribed injection quantity Qmin or larger, this restart being made with the required injection quantity at this time.

Abstract: A spark ignition internal combustion engine (2) performs ignition within a fixed ignition crank angle range. The operation control device comprises a programmable controller (1) and a unit crank angle sensor (9) outputting a unit crank angle signal on each unit crank angle. The controller (1) calculates the engine rotation speed based on the unit crank angle signals (S1). By preventing the calculation of the engine rotation speed based on the unit crank angle signals detected in the ignition crank angle range, errors in the calculation of the engine rotation speed resulting from engine ignition noise are eliminated and a precise engine rotation speed is obtained.