Multitec system
Note: There are no provisions for adjusting or changing the idle speed; when checking the idle speed, remember that it can constantly change under the control of the ECU.
2. The Multec system is essentially a simple air/fuel mixing method that replaces a single jet carburetor mounted in the throttle body. Therefore, this type of system is also called throttle body injection (TBi), Central fuel injection (CFi) or one- (or mono) point injection. The complete system is best explained by considering it as three subsystems: the fuel supply system, the air sensing system, and the electrical control system.
3. The fuel supply system consists of a fuel tank (with electric fuel priming pump submerged inside), fuel filter, fuel injector and pressure regulator (installed in throttle body), as well as hoses and tubes connecting all these nodes. With the ignition on (or when the engine is running, models with X16 SZ engine) the pump is supplied with power through the pump relay and fuse 11, controlled by the Electronic Control Unit (ECU). Pump Pumps fuel through the fuel filter to the injector. The fuel pressure is controlled by a regulator which returns excess fuel to the tank when the pressure rises.
4. The airflow sensing system contains an intake air temperature control subsystem and an air filter, but the main components are in the throttle body assembly. It has an injector that injects fuel into the back of the throttle and a throttle potentiometer. The potentiometer is connected to the throttle shaft and provides the ECU with information regarding the degree of throttle opening by transmitting a varying voltage. The idle air control stepper motor is controlled by the ECU and is designed to maintain the idle speed.
5. The electrical part of the fuel injection system consists of the ECU and all the sensors that supply the information management system, plus the actuators that control the entire system. Note that the ignition system is controlled by the same ECU.
6. The manifold pressure sensor is connected by a hose to the intake manifold. Changes in intake manifold pressure are converted into electrical signals that are used by the ECU to determine engine load. The operation of the throttle potentiometer is explained earlier.
7. Information regarding engine speed and crankshaft position comes from the distributor on models with the C16 NZ engine and from the speed / crankshaft position sensor on models with the C16 NZ2, X16 SZ and C18 NZ engines.
8. The odometer provides the ECU with vehicle speed information, and the coolant temperature sensor provides engine temperature information. The knock sensor is located in the cylinder block between cylinders 2 and 3 on XI6 SZ engines, and provides the ECU with additional information when pre-ignition is detected during combustion.
9. All these signals are compared by the ECU with the preset values stored in memory. Based on this information, the ECU selects output values corresponding to these values. It controls the ignition booster unit, changing the ignition timing as required. The fuel injector is controlled by changing the open time, enriching or leaning the mixture, depending on the mode of operation. The stepper motor adjusts the idle speed by controlling the air. The priming pump relay controls the fuel supply and the oxygen sensor. The values of mixture, idle speed and ignition timing are constantly changed by the ECU to improve engine start-up, warm-up, to maintain idle speed, acceleration and smooth running. The injectors also turn off during engine braking to improve fuel economy and reduce exhaust emissions. Additionally, on X16 SZ engines, the ECU also controls the operation of the carbon filter valve in the vapor recovery system.
10. The oxygen sensor is screwed into the exhaust manifold and the ECU has constant feedback. Based on this data, the unit constantly adjusts the mixture to provide the best conditions for the efficient operation of the catalytic converter.
11. As long as the oxygen sensor is not fully warmed up, there is no feedback and the ECU uses the programmed values to determine the correct injector opening time. When the probe warms up to normal operating temperature, the tip (oxygen sensitive) sends a varying voltage to the ECU depending on the amount of oxygen in the exhaust gases. If the inlet air/fuel mixture is too rich, there is little oxygen in the exhaust gases and the sensor sends out a low voltage signal. The voltage increases as the mixture becomes leaner and the amount of oxygen in the exhaust gases increases. The maximum conversion ratio occurs when the input air-fuel mixture is maintained in the chemically correct ratio for complete combustion of gasoline 14.7 parts air to 1 part fuel (stochimetric number). The output voltage of the sensor varies over a large range, the ECU uses this variable signal to correct the input air/fuel mixture ratio by changing the duration of the fuel injector opening.
12. In addition, the ECU has a diagnostic mode, and can receive and transmit information through the diagnostic connector, so you can perform diagnostics and tuning with Opel TECH1 test equipment.
Motronic system
13. The Motronic system has several different versions, depending on the model. The system is fully controlled by the Motronic engine management system (Section 5), which also controls the ignition timing.
14. Fuel is pumped from the fuel tank mounted at the rear of the vehicle by an electric fuel priming pump located under the vehicle and passes through the pressure regulator to the fuel line. The fuel line is a reservoir for four fuel injectors that inject fuel into the intake tracts of the cylinders. On engines with a single overhead camshaft, the fuel injectors receive one pulse, which opens them simultaneously once per crankshaft revolution. Double overhead cam engines use a sequential fuel injection system, whereby each injector receives its own electrical pulse, and the four injectors operate independently, providing more precise control of fuel delivery to each cylinder. The duration of the electrical pulse determines the amount of injected fuel, the duration of the pulse is calculated by the Motronic unit based on information received from various sensors.
15. On engines with a single overhead camshaft, the intake air passes from the air filter to the air flow meter, and then through the throttle valve to the intake tracts of the cylinders. The flap in the airflow meter deflects depending on the strength of the airflow: this deflection is converted into an electrical signal and sent to the Motronic unit. The potentiometer screw on the airflow meter allows you to adjust the idle mixture by changing the reference voltage going to the Motronic unit.
16. On engines with double overhead camshafts, the inlet air passes from the air filter to the air flow meter (a wire carrying a current of some voltage), and further through the assembly of the 2-position throttle body to the intake tracts of the cylinders. The electrical current required to maintain a constant wire temperature in an airflow meter is proportional to the mass of airflow cooling the wire. The current is converted into a signal supplied to the Motronic unit. The throttle body contains two dampers that gradually open. A potentiometer screw located on the air flow meter allows you to adjust the idle mixture by changing the reference voltage going to the Motronic unit.
17. The throttle position sensor allows the Motronic unit to calculate the position of the throttle valve, and on some models, the degree of its opening. In this way, additional fuel can be supplied during acceleration when the throttle is suddenly opened. Information from the throttle position sensor is also used to cut off fuel during engine braking, thus improving fuel economy and reducing harmful emissions.
18. Idle speed is controlled by a variable orifice valve that controls the amount of air that is allowed to bypass the throttle. The valve is controlled by the Motronic unit; and direct adjustment of the idle speed is not possible.
19. Additional sensors provide the Motronic unit with information about the coolant temperature, air temperature and, on models with a catalytic converter, the oxygen content in the exhaust gas.
20. The fuel filter is built into the fuel supply line, cleaning the fuel before it is fed to the injectors.
21. The fuel pump cut relay is controlled by the Motronic unit, which cuts off the power supply to the fuel priming pump, causing the engine to turn off with the ignition on if any malfunction occurs. All models since 1993 are equipped with Motronic systems, the fuel priming pump is located inside the fuel tank.
22. Late system M2.8 - basically the same as early system M2.5 except the following:
- a) Tape meter of air flow mass - the previously used block with a live wire, on the M2.8 system was replaced by a tape meter of air flow mass. Its principle of operation is similar to the old one, except that a thin electrically heated plate is used instead of a wire. The constant temperature of the plate is maintained by an electric current that varies depending on the mass of inlet air passing by the plate. The current required to maintain a constant plate temperature is proportional to the mass of the inlet air flow. The current is converted into a signal that is fed to the Motronic unit.
- b) Inlet air temperature sensor - located in the hose between the air mass tape measure and the air filter, and is designed to accurately control the temperature of the inlet air. Signals from this sensor, in combination with other sensors, are used to determine the hot start condition. The Motronic unit then processes these signals and changes the injector open duration.
- c) Throttle potentiometer on the M2.8 system The throttle potentiometer replaces the throttle switch used on early models.
Simtec system
23. Instead of mechanical parts, a large number of electronic components are used: sensors and actuators with the Simtec engine management system. They give more accurate data, as well as a greater ability to freely control engine modes.
24. The control unit is equipped with an electronic ignition control system called Microprocessor Inductive Control System ("Microprocessor Spark Timing System, inductive triggered" or MSTS-i), and components such as a mechanical ignition distributor are no longer needed. The control unit is located behind the trim panel, in the footwell on the right (door post).
25. The ignition coil has been replaced by a double coil, which is switched by the control unit.
26. The camshaft sensor indicates a certain position when the crankshaft passes the inductive head. It is designed to determine the TDC ("top dead center"), crankshaft angle and engine speed. The signals are used by the control unit to calculate the ignition timing and for the fuel injection system.
27. The air flow mass tape meter measures the mass of air entering the engine. The system uses this information to calculate the correct amount of fuel to inject into the engine.
28. Inlet air temperature sensor (NTC), installed in the air intake duct between the air filter and the warm air flow meter.
29. The carbon filter control valve is actuated by the system. Tank ventilation is checked by lambda control (or oxygen sensor) and corrected by the control unit computer.
30. There is also a detonation control system. It eliminates the need for octane adjustment, this is done automatically by the control unit.
31. This engine is also equipped with an exhaust gas recirculation valve (re-burning of waste gases) and secondary air injection (AIR — Air Injection Reactor), all of which comply with the latest European exhaust emission regulations (since 1996). The system returns a certain amount of exhaust gas to the combustion path. As a result, the formation of nitrogen oxides is reduced (NOx). The secondary air injection system has a blower that introduces air into the exhaust manifold, reducing the CO and HC content in the exhaust gases.
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