Working principle and control strategy of motorcycle EFI system

The EFI motorcycle is a new type of motorcycle. It controls the injector to inject oil to the cylinders that need to work according to the load of the engine through a microcomputer, and the cylinders that don't work don't give oil. EFI motorcycles are more fuel-efficient than traditional carburetor motorcycles and more than 20% more fuel-efficient than motorcycles with the same carburetor. Because the functions of digital ignition and fuel injection are realized, the fuel consumption is reduced and the emission is improved, so it is more environmentally friendly than carburetor cars and directly meets the European emission standard 1 1. At the same time, it also has the characteristics of easy start, strong explosive force and stable idle speed.

Working principle: the carburetor supplies oil to the engine by mechanical means, and the relationship between the oil supply and the speed or throttle opening can only be linear, which cannot guarantee that the air-fuel ratio of the engine can reach the ideal in all working conditions and all weather. At the same time, when the state of the engine itself changes, the carburetor can't improvise, resulting in a lot of energy waste, which is not conducive to combustion, thus increasing fuel consumption and worsening emissions. EFI motorcycle adopts EFI technology, eliminates carburetor device with EFI system device, and adopts microcomputer (ECU) equipped with EFI special software to realize real-time intelligent control of engine fuel supply and ignition. The fuel supply is extremely accurate, so that the engine can reach the best air-fuel ratio and ignition angle at any time under any working condition and environment, thus reducing fuel consumption, improving emissions and greatly improving the comprehensive performance of motorcycles.

Classification and comparison: EFI motorcycles can be roughly divided into open-loop EFI motorcycles and closed-loop EFI motorcycles.

Open-loop EFI motorcycle is not necessarily better than carburetor; Closed-loop EFI motorcycles are quite in place, and their functions and functions are basically the same as those of automobiles. Closed-loop EFI motorcycle can adjust the fuel injection quantity of electric nozzle according to the oxygen content in muffler, and can also change the intake pressure according to the change of external atmospheric pressure. At present, domestic motorcycles are basically open-loop EFI motorcycles.

EFI engine: The EFI device of motorcycle engine generally consists of fuel injection circuit, sensor group and electronic control unit (ECU). If the injector is installed in the original carburetor position, that is, there is only one gasoline injection point in the whole engine, this is a single-point EFI; If the injector is installed on the intake pipe of each cylinder, that is, gasoline is injected into the cylinder from multiple places (at least one injection point for each cylinder), this is multi-point injection.

Advantages and disadvantages of motorcycle open loop and closed loop: open loop is not really EFI, it is between carburetor and EFI, and it is easier to start than carburetor. Only a closed loop and accurate oil supply by ECU is EFI, which can make corresponding automatic adjustment in different environmental climates, and there will be no idling jitter of vehicles in plateau climate. Motorcycles will enter the era of all-electric injection sooner or later.

Structural component: ECU: abbreviation of electronic control unit, which is actually an integrated circuit board. It is responsible for converting the electrical signals sent by various sensors into digital signals, processing them with the programs stored in the read-write memory of the circuit board, and then sending out control signals to control the fuel injection of the fuel injector and the ignition of the high-voltage coil.

Fuel injector: a precise component responsible for injecting and atomizing fuel, usually installed at the intake pipe end of the throttle body.

Throttle body: it is equivalent to the throat cavity of carburetor, but there are no other parts on the carburetor, only an idle bypass airway. When the temperature of the engine rises at idle speed and low speed, the air intake will be insufficient due to the decrease of heating density. At this time, an appropriate amount of air will be supplemented by controlling the bypass air channel.

Throttle position sensor (TPS): connected with the throttle valve plate. When the angle of the throttle valve plate changes and the opening increases, the components in the sensor rotate with the valve plate. The throttle position sensor is actually a variable potentiometer. When it rotates synchronously with the throttle, it converts the angle and angle change rate of the throttle into voltage signals and sends them to ECU. This signal mainly represents the load of the engine.

Air temperature sensor: used to measure the intake air temperature. It is a thermistor. The higher the temperature, the smaller the resistance value, which causes the voltage change and sends it to ECU.

Intake air flow sensor: The intake grille made of special material is electrified during operation to keep its temperature constant. When the intake air volume changes, the intake grille is cooled, and at this time, more current is needed to raise its temperature to the original standard temperature, and the required current is proportional to the intake air volume, so the intake air volume can be measured.

Crankshaft angle sensor: composed of pulse gear ring and magnetoelectric coil. The pulse gear ring is installed on the flywheel and rotates with the crankshaft. When rotating, the electromagnetic coil senses the signal of the pulse gear ring and converts it into a voltage signal and sends it to ECU.

Oxygen sensor: mainly sends the information of oxygen content in exhaust gas to ECU, and ECU adjusts the air-fuel ratio according to the signal to make the three-way catalytic converter have the highest efficiency and the least pollution emission. The oxygen sensor is generally installed in the exhaust manifold, and its voltage output value changes with the change of oxygen concentration in the exhaust gas. ECU judges the air-fuel ratio according to the voltage change of oxygen sensor, and adjusts the fuel injection quantity accordingly. Therefore, even if the air-fuel ratio changes due to the wear of engine parts, the oxygen sensor can feed back to ECU in time to realize the closed-loop control of the optimal air-fuel ratio of the engine.

Production method

Classification of EFI technology

Function of EFI system: EFI system is actually a system integrating carburetor and igniter, which provides suitable fuel for engine under different working conditions.

And control the ignition time to ensure the normal operation of the engine.

Advantages of EFI system: Compared with carburetor fuel supply, EFI system has more accurate control, and can realize accurate fuel supply control under different working conditions, and the ignition angle can be changed as required. In addition, the closed-loop EFI system with oxygen sensor can correct the fuel injection quantity according to the actual situation of the engine even if the motorcycle is used for a period of time, so as to better control emissions and improve fuel economy. Classification of EFI system

EFI system with gasoline pump: Oil supply principle: After the ignition switch is turned on, the gasoline pump in the oil tank is electrified for operation.

efi motorcycle

Send the oil to the injector. There is a fuel pressure regulator in the oil circuit, which will send the fuel to the injector after the fuel pressure is stable, and the remaining fuel will flow back to the fuel tank through the oil return pipe after one injection by the fuel injection pump.

Control signal input: The signals measured in real time by sensors such as throttle position sensor, intake flow sensor, air temperature sensor, engine temperature sensor, crankshaft position sensor and oxygen sensor are sent to ECU.

Signal processing and output: After receiving signals from various sensors, ECU (Central Control Unit) calculates the required fuel injection amount according to the built-in calculation program, and sends pulse signals with different wavelengths to the fuel injector according to the fuel injection amount, so as to achieve the purpose of supplying different amounts of fuel under different working conditions by controlling the opening time of the fuel injector. At the same time, the primary voltage is provided to the ignition coil in time to achieve the purpose of ignition. EFI system without gasoline pump: Oil supply principle: Like ordinary motorcycles, the gasoline in the fuel tank is sent to the injector by gravity.

efi motorcycle

After the fuel injector finishes spraying, the remaining fuel flows back to the fuel tank through the fuel return pipe.

Control signal input: The signals measured in real time by sensors such as throttle position sensor, intake flow sensor, air temperature sensor, engine temperature sensor, crankshaft position sensor and oxygen sensor are sent to ECU. Signal processing and output:

After receiving the signal from the sensor, ECU (Central Control Unit) calculates the required fuel injection amount according to the built-in calculation program, sends pulse signals with different wavelengths to the fuel injector according to the fuel injection amount, and pressurizes the fuel by controlling the action of the plunger in the fuel injector. When the pressure exceeds the pressure control valve, the valve opens, and the fuel is ejected. The fuel quantity is also controlled by the length of the pulse signal. The longer the signal wavelength is, the longer the electromagnetic coil around the plunger is energized, the longer the plunger moves, and the greater the fuel injection. Comparison of two EFI systems;

Fuel supply: The FI system has a fuel pump, so the fuel tank needs to be rebuilt, which increases the power consumption. At the same time, because it is high-pressure oil supply, the requirements for oil pipes and other parts are higher. For example, the tubing should not be too soft to ensure the fuel pressure. Because it is pressure oil supply, there is no high or low requirement for the position of fuel tank and injector.

The DCP system uses gravity oil supply, so the oil tank does not need to be replaced, nor does it increase power consumption, and there is no special requirement for oil pipes and other components. However, due to gravity oil supply, the position of the oil outlet of the fuel tank must be higher than that of the fuel injector, which may be inconvenient to arrange on some models. Control signal input: There is no difference in control signal input between the two systems.

Signal processing and output: there is not much difference between the two systems in signal processing and output, mainly because the injectors of DCP system are different. Because the injector of DCP system is equivalent to the injector and fuel pump integrated in FI system, its structure is more complicated and its volume is generally larger.

Main advantages

1, accurate fuel supply, easy control of air-fuel ratio and good fuel economy;

2. The ignition adopts digital ignition mode, which can be ignited at the best ignition moment under any working condition, and the combustion is full and thorough; 3. The air-fuel ratio can be controlled to fluctuate around λ= 1, which makes the three-way catalyst have high conversion efficiency and good emission performance for CO, HC and NOX;

4, good starting performance, smooth transition under variable working conditions such as acceleration and deceleration, and good driving performance;

5. Compared with carburetor motorcycle, EFI has more accurate ignition time, but leaner air-fuel ratio, and the dynamic performance of the engine is equivalent to that of fuel.