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vilant · 03-14-2013

5-Power Modes- The driver can select two engine power modes, “FULL” or “NORMAL” power, with a console mounted key switch. This switch is wired into the ECM, and allows the driver to determine the engine output by controlling the secondary port throttle valves, secondary injectors, and secondary fuel pump operation. When the key is in “Full” power position, the ECM enables the secondary operation only if no trouble codes are stored and other criteria are met such as; engine oil temperature (not too hot or too cold), throttle position, manifold air pressure, and engine speed. If all conditions are met, the ECM consecutively turns “On”: the secondary port throttle valve solenoid (causing the valves to open), the secondary injectors to provide the additional fuel required for full engine power operation, and then the secondary fuel pump relay/secondary fuel pump to maintain fuel system pressure. When the secondary injectors are “On”, total fuel flow to each cylinder is divided equally between the primary and secondary injectors. Whenever Wide Open Throttle (WOT) is commanded and the secondary port throttle valves are enabled, the ECM continues to monitor oxygen sensor outputs. If a lean condition (low O2 sensor voltage) exists for more than 2 seconds, a Code 55(Fuel Monitor Lean) is set, and secondary port throttle/secondary injector/secondary fuel pump operation is disabled.

6-Fuel Cut-off Mode- To prevent possible engine damage from over-speed, the ECM cuts off fuel from all injectors at approximately 7000 RPM in the “Full” power position and 5000 RPM in the “Normal” power position. If a Code 61(Secondary Port Throttle System Error) is stored in the ECM, secondary port throttle/secondary injector/ secondary fuel pump operation are disabled, and fuel cut-off occurs at approximately 3000 RPM.

7-Deceleration Mode- When the driver releases the accelerator pedal, air flow to the engine is reduced. The corresponding changes in throttle position and manifold air pressure are relayed to the ECM, which reduces the injector pulse width to reduce fuel flow. If the deceleration is very rapid, or for very long periods (such as long closed throttle coast-down), the ECM shuts fuel completely “Off”, to protect the catalytic converter.

8-Battery Voltage Correction Mode- When the battery voltage is low, the ECM can compensate by; increasing the amount of fuel delivered, increasing the idle RPM, and increasing ignition dwell time.

The original multi-point fuel injection (MPFI) injectors are solenoid-operated metering valves, controlled by the ECM, that deliver pressurized fuel to a single cylinder. The ECM energizes the injector solenoid, which opens a ball valve, allowing fuel to flow past the ball valve, and through a recessed flow director plate. The director plate has 6 machined holes that control the fuel flow, generating a conical spray pattern of finely atomized fuel at the injector tip. Fuel is directed at the intake valve, causing it to become further atomized and vaporized before entering the combustion chamber.

Continuous Fuel Injection- provides a continuous spray of fuel from each injector at a point in the intake port just before the each intake valve. Because the fuel entering the cylinder is controlled by the intake valve, the continuous system will fulfill the requirements of a gasoline engine. Timed injection systems, though a necessity on diesel engines, are costlier than continuous systems and used on gasoline engines only when more precise fuel metering is desired. In continuous systems, fuel is delivered to the mixture control unit by the fuel pump. The pressure regulator maintains the fuel pressure and returns excess to the gas tank. The mixture control unit regulates the amount of fuel that is sent to the injectors based on the amount of airflow through the intake and the engine temperature. The mixture control unit on mechanical systems will be operated by the airflow sensing plate and warm-up regulator. Electronic systems will have the information processed by a computer that will regulate the fuel injection rate. The accelerator pedal regulates air flow through the intake by opening and closing the throttle valve. A cold-start injector is installed in the intake to provide a richer mixture during start-up. It works in conjunction with the auxiliary air valve, their function is to speed up the engine idle during warm-up. Both are controlled through a thermal sensor in the engine coolant line.

Throttle Body Injection- is a form of continuous injection that uses 1 or 2 injectors delivering fuel from 1 central point in the intake manifold. It does not provide the precise fuel distribution as the previous systems, but is cheaper than both and still more precise than a carburetor. The throttle body injection unit is usually an integral one, containing all of the major system components, in most cases. The unit mounts on the intake manifold in the same manner as a carburetor. Airflow sensors and electronic computers usually are mounted in the air cleaner body.

Turbochargers and Superchargers

Turbo or supercharging is a method of increasing engine volumetric efficiency by forcing the air/fuel mixture into the intake rather than merely allowing the pistons to draw it in naturally. By doing this you can, in some cases, push the volumetric efficiency over 100%. Engines must be modified to operate properly because the extra air/fuel mixture will cause higher compression pressures, which could result in detonation.

Turbochargers- use the force of the engine exhaust stream to force the air/fuel mixture into the engine. It consists of a housing containing 2 chambers. One chamber consists of turbine that is spun by hot exhaust gases directed at it. The turbine shaft drives an impeller that is located in other chamber. The spinning impeller draws in the air/fuel mix and forces it into the engine. Because the volume of exhaust gases increases with engine load and speed, the turbocharger speed will increase proportionally, keeping the manifold pressure boost fairly uniform. A device called a “waste gate” is installed to control manifold pressure. It is a valve that when open, allows exhaust gas to bypass the turbine, which in turn reduces intake pressure. The waste gate valve is operated by a diaphragm which is controlled by manifold pressure. The diaphragm will open the valve whenever the manifold pressure reaches the desired maximum (See figure 23).

Superchargers- are engine driven air pumps that force the air/fuel mixture into the engine. There are 3 basic types; centrifugal, Rootes, and vane (See figure 23).
1-Centrifugal Supercharger- has an impeller equipped with curved vanes. As the impeller is driven by the engine, it draws air into its center and throws it off at its rim. The air is then pushed along the inside of the circular housing. The diameter of the housing gradually increases to the outlet where the air is pushed out.
2-Rootes Supercharger- is of the positive displacement type and consists of 2 rotors inside a housing. As the rotors are driven by the engine, air is trapped between them and the housing. It is then carried to the outlet where it is discharged. The rotors and the housing in this type of supercharger must maintain very tight clearances, which makes them very sensitive to dirt.
3-Vane Supercharger- is also the positive displacement type and consists of an integral steel rotor and shaft. The rotor has 2 sliding vanes placed 180* apart in slots in the rotor and are pressed against the body of the bore by springs in the slots. The rotor revolves in the body, the bore of which is eccentric to the rotor. When the shaft is rotated by the engine, usually by a belt, the vanes pick up air at the inlet and carry it around the body to the outlet where it is discharged. Pressure is produced by the wedging action of the air as it is forced toward the outlet port.
It should be noted that on carbureted engines, superchargers will deliver air to the carburetor via a pressure box.

03-14-2013	#6
vilant Join Date: Jun 2012 Location: PA Posts: 770	Re: Automotive principals 101 5-Power Modes- The driver can select two engine power modes, “FULL” or “NORMAL” power, with a console mounted key switch. This switch is wired into the ECM, and allows the driver to determine the engine output by controlling the secondary port throttle valves, secondary injectors, and secondary fuel pump operation. When the key is in “Full” power position, the ECM enables the secondary operation only if no trouble codes are stored and other criteria are met such as; engine oil temperature (not too hot or too cold), throttle position, manifold air pressure, and engine speed. If all conditions are met, the ECM consecutively turns “On”: the secondary port throttle valve solenoid (causing the valves to open), the secondary injectors to provide the additional fuel required for full engine power operation, and then the secondary fuel pump relay/secondary fuel pump to maintain fuel system pressure. When the secondary injectors are “On”, total fuel flow to each cylinder is divided equally between the primary and secondary injectors. Whenever Wide Open Throttle (WOT) is commanded and the secondary port throttle valves are enabled, the ECM continues to monitor oxygen sensor outputs. If a lean condition (low O2 sensor voltage) exists for more than 2 seconds, a Code 55(Fuel Monitor Lean) is set, and secondary port throttle/secondary injector/secondary fuel pump operation is disabled. 6-Fuel Cut-off Mode- To prevent possible engine damage from over-speed, the ECM cuts off fuel from all injectors at approximately 7000 RPM in the “Full” power position and 5000 RPM in the “Normal” power position. If a Code 61(Secondary Port Throttle System Error) is stored in the ECM, secondary port throttle/secondary injector/ secondary fuel pump operation are disabled, and fuel cut-off occurs at approximately 3000 RPM. 7-Deceleration Mode- When the driver releases the accelerator pedal, air flow to the engine is reduced. The corresponding changes in throttle position and manifold air pressure are relayed to the ECM, which reduces the injector pulse width to reduce fuel flow. If the deceleration is very rapid, or for very long periods (such as long closed throttle coast-down), the ECM shuts fuel completely “Off”, to protect the catalytic converter. 8-Battery Voltage Correction Mode- When the battery voltage is low, the ECM can compensate by; increasing the amount of fuel delivered, increasing the idle RPM, and increasing ignition dwell time. The original multi-point fuel injection (MPFI) injectors are solenoid-operated metering valves, controlled by the ECM, that deliver pressurized fuel to a single cylinder. The ECM energizes the injector solenoid, which opens a ball valve, allowing fuel to flow past the ball valve, and through a recessed flow director plate. The director plate has 6 machined holes that control the fuel flow, generating a conical spray pattern of finely atomized fuel at the injector tip. Fuel is directed at the intake valve, causing it to become further atomized and vaporized before entering the combustion chamber. Continuous Fuel Injection- provides a continuous spray of fuel from each injector at a point in the intake port just before the each intake valve. Because the fuel entering the cylinder is controlled by the intake valve, the continuous system will fulfill the requirements of a gasoline engine. Timed injection systems, though a necessity on diesel engines, are costlier than continuous systems and used on gasoline engines only when more precise fuel metering is desired. In continuous systems, fuel is delivered to the mixture control unit by the fuel pump. The pressure regulator maintains the fuel pressure and returns excess to the gas tank. The mixture control unit regulates the amount of fuel that is sent to the injectors based on the amount of airflow through the intake and the engine temperature. The mixture control unit on mechanical systems will be operated by the airflow sensing plate and warm-up regulator. Electronic systems will have the information processed by a computer that will regulate the fuel injection rate. The accelerator pedal regulates air flow through the intake by opening and closing the throttle valve. A cold-start injector is installed in the intake to provide a richer mixture during start-up. It works in conjunction with the auxiliary air valve, their function is to speed up the engine idle during warm-up. Both are controlled through a thermal sensor in the engine coolant line. Throttle Body Injection- is a form of continuous injection that uses 1 or 2 injectors delivering fuel from 1 central point in the intake manifold. It does not provide the precise fuel distribution as the previous systems, but is cheaper than both and still more precise than a carburetor. The throttle body injection unit is usually an integral one, containing all of the major system components, in most cases. The unit mounts on the intake manifold in the same manner as a carburetor. Airflow sensors and electronic computers usually are mounted in the air cleaner body. Turbochargers and Superchargers Turbo or supercharging is a method of increasing engine volumetric efficiency by forcing the air/fuel mixture into the intake rather than merely allowing the pistons to draw it in naturally. By doing this you can, in some cases, push the volumetric efficiency over 100%. Engines must be modified to operate properly because the extra air/fuel mixture will cause higher compression pressures, which could result in detonation. Turbochargers- use the force of the engine exhaust stream to force the air/fuel mixture into the engine. It consists of a housing containing 2 chambers. One chamber consists of turbine that is spun by hot exhaust gases directed at it. The turbine shaft drives an impeller that is located in other chamber. The spinning impeller draws in the air/fuel mix and forces it into the engine. Because the volume of exhaust gases increases with engine load and speed, the turbocharger speed will increase proportionally, keeping the manifold pressure boost fairly uniform. A device called a “waste gate” is installed to control manifold pressure. It is a valve that when open, allows exhaust gas to bypass the turbine, which in turn reduces intake pressure. The waste gate valve is operated by a diaphragm which is controlled by manifold pressure. The diaphragm will open the valve whenever the manifold pressure reaches the desired maximum (See figure 23). Superchargers- are engine driven air pumps that force the air/fuel mixture into the engine. There are 3 basic types; centrifugal, Rootes, and vane (See figure 23). 1-Centrifugal Supercharger- has an impeller equipped with curved vanes. As the impeller is driven by the engine, it draws air into its center and throws it off at its rim. The air is then pushed along the inside of the circular housing. The diameter of the housing gradually increases to the outlet where the air is pushed out. 2-Rootes Supercharger- is of the positive displacement type and consists of 2 rotors inside a housing. As the rotors are driven by the engine, air is trapped between them and the housing. It is then carried to the outlet where it is discharged. The rotors and the housing in this type of supercharger must maintain very tight clearances, which makes them very sensitive to dirt. 3-Vane Supercharger- is also the positive displacement type and consists of an integral steel rotor and shaft. The rotor has 2 sliding vanes placed 180* apart in slots in the rotor and are pressed against the body of the bore by springs in the slots. The rotor revolves in the body, the bore of which is eccentric to the rotor. When the shaft is rotated by the engine, usually by a belt, the vanes pick up air at the inlet and carry it around the body to the outlet where it is discharged. Pressure is produced by the wedging action of the air as it is forced toward the outlet port. It should be noted that on carbureted engines, superchargers will deliver air to the carburetor via a pressure box. Last edited by vilant; 05-27-2013 at 09:34 PM.