Maximus
12-18-05, 01:13 AM
Various injection schemes
Indirect injection
This may be single point where the fuel is injected using one or more nozzles, located centrally either just upstream or just downstream of the throttle housing, or multi point where each cylinder has its own injector in the inlet manifold. The nozzles may be opened using the pressure in the fuel system or there may be a solenoid on the injector that will pulse it open and closed in a duty cycle according to the desired fuel requirement.
Throttle-body injection
Electronic throttle-body injection (normally called TBI, though Ford used the abbreviation, CFI) was introduced in the early 1980s as a transition technology to fully electronic port injection. The system injects fuel into the throttle-body (a wet system), because fuel passes through the intake runners like a carburetor system. This system had all the drawbacks of a carburetor, and all the drawbacks of early automotive electronics as well. Computer-controlled TBI was inexpensive, and was primarily a transition phase from carburetors to port fuel injection.
Continuous injection
Bosch's K-Jetronic or CIS used a continuous injection method. Gasoline was pumped through a large control valve called a fuel distributor, which sat atop a control vane mounted in the air intake pathway. The fuel went from there to the injectors on each cylinder's intake port (which were simply nozzles with no valves in them). The system worked by varying fuel mixture based on the amount of air flowing past the control vane. This system was used for many years on Volkswagen and Mercedes-Benz cars. There was also a variant of the system called KE-Jetronic that used an oxygen sensor to fine-tune the mixture.
Central port injection
General Motors developed a new "in-between" technique called "central port injection" (CPI) or "central port fuel injection" (CPFI). It uses tubes from a central injector to spray fuel at the intake port rather than the throttle-body (it is a dry system). However, fuel is continuously injected to all ports simultaneously, which is less than optimal.
Sequential central point injection
GM refined the CPI system into a sequential central port injection (SCPI) system in the mid-1990s. It used valves to meter the fuel to just the cylinders that were in the intake phase. This worked well on paper, but the valves had a tendency to stick. Fuel injector cleaner sometimes worked, but the system remained problematic.
Multi-port fuel injection
The goal of all fuel injection systems is to carefully meter the amount and timing of fuel to each cylinder. This is achieved with the more sophisticated fuel injection systems, often called multi-port fuel injection (MFI) or sequential port fuel injection (SFI). On gasoline applications, the system uses a single injector per cylinder and injects fuel immediately ahead of the intake valves.
Direct injection
See also: Gasoline Direct Injection
Since mid-2000s, many diesel engines feature direct injection (DI). The injection nozzle is placed inside the combustion chamber itself and the piston incorporates a depression (often toroidal) which is where initial combustion takes place. Direct injection diesel engines are generally more efficient and cleaner than indirect injection engines, but tend to be noisier; which is being addressed in newer common rail designs.
Some hi-tech petrol engines utilize this system as well. This can improve the engine's volumetric efficiency by permitting more design freedom for the air induction system. The injector also features distinct spray modes to better manage combustion characteristics.
Evolution
Pre-Emission Era
Frederick William Lanchester joined the Forward Gas Engine Company Birmingham, England in 1889. He carried out what were possibly the earliest experiments with fuel injection.
Indirect fuel injection has been used in diesel engines since the mid 1920s, almost from their introduction (due to the higher energy required for diesel to evaporate). The concept was adapted for use in petrol-powered aircraft during World War II, and direct injection was employed in some notable designs like the Daimler-Benz DB 603 and later versions of the Wright R-3350 used in the B-29 Superfortress.
A mechanical gasoline injection system developed by Bosch was first used in a car in 1955 with the introduction of the Mercedes-Benz 300SL. An electronic fuel injection system was also developed by the Bendix Corporation, but development was abandoned as being too impractical at the time; there did not yet exist solid state sensors or mass-produced transistors suitable for further development. The patents were subsequently sold to Bosch.
In 1957, Chevrolet introduced a mechanical fuel injection option for its 283 V8 engine, made by General Motors' Rochester division. This system used a single central plunger to feed fuel to all eight cylinders, in contrast to Mercedes' individual plunger for each of the six cylinders, but it nevertheless produced 283 hp (211 kW) from 283 in³ (4.6 L), making it the first production engine in history to exceed 1 hp/in³ (45.5 kW/L).
Fuel injection systems such as Hilborn were occasionally used on modified American V8 engines in high performance automobiles of the 1960s, in drag racing, oval racing, and road racing. The primary motivation behind these systems was, however, to reduce the airflow restriction in the air intake at wide-open throttle by eliminating the venturi, with little attention to low speed or closed throttle operation. Therefore, these racing-derived systems were generally quite unsuitable for street use, although occasionally an individual would take up the challenge of adapting such an engine.
Post emission era
In 1968, in the United States, the Environmental Protection Agency began to restrict exhaust emissions and enacted a series of automobile emissions control laws coming into effect over the next several years. This change became the primary driver behind the adoption of fuel injection systems on a mass scale. Bosch developed the first production electronic fuel injection system, called D-Jetronic (D for Druck, the German word for pressure), which was first used on the Volkswagen 411 in 1967. This was a speed/density system, using intake manifold pressure and engine speed to calculate fuel requirements. The system used all analog discrete electronics and an electro-mechanical pressure sensor, but the sensors were susceptible to vibration and dirt. These systems were adopted by VW, Mercedes-Benz, Porsche, Saab and Volvo. Lucas licensed the system and production units for Jaguar. Bosch replaced this with a mass-flow system, initially using a mechanical airflow meter to judge how much fuel to inject. This system, L-Jetronic (L for Luft, German for air), first appeared on the 1974 Porsche 914, and was very widely adopted on European cars of that period. It was also licensed by Japanese firms and appeared on Japanese cars a short time later.
In 1975, California's emissions regulations, the most stringent in the world, required manufacturers to resort to a catalytic converter, which act as a "catalyst", when exposed to gasoline combustion byproducts; no other technology available could meet the California regulations. An oxidation catalyst was designed into the vehicle's exhaust system. When hot products of combustion, unburned hydrocarbons and carbon monoxide, are exposed to the catalyst material (platinum and/or palladium), these compounds are nearly all oxidized into water and carbon dioxide. Stricter legislation to reduce compounds called oxides of nitrogen occurred in 1980. This required a reduction catalyst (rhodium) to reduce the various nitrogen oxides into free nitrogen and oxygen. The introduction of the catalyst reduced tailpipe emission to approximately 10% of the pre-regulated 1960 level. Nearly all vehicles of this vintage used a carburetor.
Catalytic converters will not tolerate exposure to tetraethyl lead, an octane enhancer in gasoline, and they will become almost totally ineffective after only a short time. Unleaded fuel became available with the introduction of catalysts.
In order to take maximum advantage of a catalyst's chemical process, excellent air/fuel ratio control is essential, which the EFI systems accomplished in two stages. The first systems were open loop, and then by 1980 closed-loop systems began to appear.
The early fuel injection systems were "open loop". This was generally fine, as long as all the components of the system were clean and within operational parameters. However, the electro-mechanical sensors often deteriorate with time, or became dirty, and it was impossible to emissions compliance over the life of the vehicle. Soon, even more stringent emissions legislation occurred. In order to address these issues, "closed loop" feedback control of EFI appeared in 1980. Closed loop fuel control is accomplished with the Lambda-Sond sensor, commonly referred to as the exhaust gas oxygen sensor, or EGO sensor, or O2 sensor. This sensor resembled a spark plug without an electrode and is designed into the exhaust system upstream of the catalyst. The EGO sensor measures the oxygen content in the exhaust. Oxygen, or the lack of it, is proportional to the air/fuel mixture ingested into the engine.
"Closed loop feedback" fuel control made possible by digital EFI systems reduced exhaust emissions to less than 1% of the 1960 models. Unleaded fuel protects the catalytic converter so this level of emission performance is durable for tens of thousands of miles.
Starting in 1982, Bosch used a mass airflow meter on their L-Jetronic system, changing the name to LH-Jetronic (L for Luft, or air, and H for Heiße-leitung, or hot-wire), as the first true sensor for actual air mass involved the use of a heated platinum wire. The LH-Jetronic system is also notable in that it was the first system to abandon an analog ECU (using mainly AF components) in favor of a digital computer, which is now the prevailing form of ECU. This further refined air/fuel ratio control.
The introduction of microprocessor controls allowed the integration of fuel injection and ignition control, with systems first appearing in 1982 (The Bosch Motronic system, which oddly reverted to using a mechanical airflow sensor until the mid-to-late 1980s). Full engine management systems came shortly afterwards, with control of all engine systems under the control of a single computer. In 2005, many new cars had multiple computers on board controlling every aspect of the car.
Indirect injection
This may be single point where the fuel is injected using one or more nozzles, located centrally either just upstream or just downstream of the throttle housing, or multi point where each cylinder has its own injector in the inlet manifold. The nozzles may be opened using the pressure in the fuel system or there may be a solenoid on the injector that will pulse it open and closed in a duty cycle according to the desired fuel requirement.
Throttle-body injection
Electronic throttle-body injection (normally called TBI, though Ford used the abbreviation, CFI) was introduced in the early 1980s as a transition technology to fully electronic port injection. The system injects fuel into the throttle-body (a wet system), because fuel passes through the intake runners like a carburetor system. This system had all the drawbacks of a carburetor, and all the drawbacks of early automotive electronics as well. Computer-controlled TBI was inexpensive, and was primarily a transition phase from carburetors to port fuel injection.
Continuous injection
Bosch's K-Jetronic or CIS used a continuous injection method. Gasoline was pumped through a large control valve called a fuel distributor, which sat atop a control vane mounted in the air intake pathway. The fuel went from there to the injectors on each cylinder's intake port (which were simply nozzles with no valves in them). The system worked by varying fuel mixture based on the amount of air flowing past the control vane. This system was used for many years on Volkswagen and Mercedes-Benz cars. There was also a variant of the system called KE-Jetronic that used an oxygen sensor to fine-tune the mixture.
Central port injection
General Motors developed a new "in-between" technique called "central port injection" (CPI) or "central port fuel injection" (CPFI). It uses tubes from a central injector to spray fuel at the intake port rather than the throttle-body (it is a dry system). However, fuel is continuously injected to all ports simultaneously, which is less than optimal.
Sequential central point injection
GM refined the CPI system into a sequential central port injection (SCPI) system in the mid-1990s. It used valves to meter the fuel to just the cylinders that were in the intake phase. This worked well on paper, but the valves had a tendency to stick. Fuel injector cleaner sometimes worked, but the system remained problematic.
Multi-port fuel injection
The goal of all fuel injection systems is to carefully meter the amount and timing of fuel to each cylinder. This is achieved with the more sophisticated fuel injection systems, often called multi-port fuel injection (MFI) or sequential port fuel injection (SFI). On gasoline applications, the system uses a single injector per cylinder and injects fuel immediately ahead of the intake valves.
Direct injection
See also: Gasoline Direct Injection
Since mid-2000s, many diesel engines feature direct injection (DI). The injection nozzle is placed inside the combustion chamber itself and the piston incorporates a depression (often toroidal) which is where initial combustion takes place. Direct injection diesel engines are generally more efficient and cleaner than indirect injection engines, but tend to be noisier; which is being addressed in newer common rail designs.
Some hi-tech petrol engines utilize this system as well. This can improve the engine's volumetric efficiency by permitting more design freedom for the air induction system. The injector also features distinct spray modes to better manage combustion characteristics.
Evolution
Pre-Emission Era
Frederick William Lanchester joined the Forward Gas Engine Company Birmingham, England in 1889. He carried out what were possibly the earliest experiments with fuel injection.
Indirect fuel injection has been used in diesel engines since the mid 1920s, almost from their introduction (due to the higher energy required for diesel to evaporate). The concept was adapted for use in petrol-powered aircraft during World War II, and direct injection was employed in some notable designs like the Daimler-Benz DB 603 and later versions of the Wright R-3350 used in the B-29 Superfortress.
A mechanical gasoline injection system developed by Bosch was first used in a car in 1955 with the introduction of the Mercedes-Benz 300SL. An electronic fuel injection system was also developed by the Bendix Corporation, but development was abandoned as being too impractical at the time; there did not yet exist solid state sensors or mass-produced transistors suitable for further development. The patents were subsequently sold to Bosch.
In 1957, Chevrolet introduced a mechanical fuel injection option for its 283 V8 engine, made by General Motors' Rochester division. This system used a single central plunger to feed fuel to all eight cylinders, in contrast to Mercedes' individual plunger for each of the six cylinders, but it nevertheless produced 283 hp (211 kW) from 283 in³ (4.6 L), making it the first production engine in history to exceed 1 hp/in³ (45.5 kW/L).
Fuel injection systems such as Hilborn were occasionally used on modified American V8 engines in high performance automobiles of the 1960s, in drag racing, oval racing, and road racing. The primary motivation behind these systems was, however, to reduce the airflow restriction in the air intake at wide-open throttle by eliminating the venturi, with little attention to low speed or closed throttle operation. Therefore, these racing-derived systems were generally quite unsuitable for street use, although occasionally an individual would take up the challenge of adapting such an engine.
Post emission era
In 1968, in the United States, the Environmental Protection Agency began to restrict exhaust emissions and enacted a series of automobile emissions control laws coming into effect over the next several years. This change became the primary driver behind the adoption of fuel injection systems on a mass scale. Bosch developed the first production electronic fuel injection system, called D-Jetronic (D for Druck, the German word for pressure), which was first used on the Volkswagen 411 in 1967. This was a speed/density system, using intake manifold pressure and engine speed to calculate fuel requirements. The system used all analog discrete electronics and an electro-mechanical pressure sensor, but the sensors were susceptible to vibration and dirt. These systems were adopted by VW, Mercedes-Benz, Porsche, Saab and Volvo. Lucas licensed the system and production units for Jaguar. Bosch replaced this with a mass-flow system, initially using a mechanical airflow meter to judge how much fuel to inject. This system, L-Jetronic (L for Luft, German for air), first appeared on the 1974 Porsche 914, and was very widely adopted on European cars of that period. It was also licensed by Japanese firms and appeared on Japanese cars a short time later.
In 1975, California's emissions regulations, the most stringent in the world, required manufacturers to resort to a catalytic converter, which act as a "catalyst", when exposed to gasoline combustion byproducts; no other technology available could meet the California regulations. An oxidation catalyst was designed into the vehicle's exhaust system. When hot products of combustion, unburned hydrocarbons and carbon monoxide, are exposed to the catalyst material (platinum and/or palladium), these compounds are nearly all oxidized into water and carbon dioxide. Stricter legislation to reduce compounds called oxides of nitrogen occurred in 1980. This required a reduction catalyst (rhodium) to reduce the various nitrogen oxides into free nitrogen and oxygen. The introduction of the catalyst reduced tailpipe emission to approximately 10% of the pre-regulated 1960 level. Nearly all vehicles of this vintage used a carburetor.
Catalytic converters will not tolerate exposure to tetraethyl lead, an octane enhancer in gasoline, and they will become almost totally ineffective after only a short time. Unleaded fuel became available with the introduction of catalysts.
In order to take maximum advantage of a catalyst's chemical process, excellent air/fuel ratio control is essential, which the EFI systems accomplished in two stages. The first systems were open loop, and then by 1980 closed-loop systems began to appear.
The early fuel injection systems were "open loop". This was generally fine, as long as all the components of the system were clean and within operational parameters. However, the electro-mechanical sensors often deteriorate with time, or became dirty, and it was impossible to emissions compliance over the life of the vehicle. Soon, even more stringent emissions legislation occurred. In order to address these issues, "closed loop" feedback control of EFI appeared in 1980. Closed loop fuel control is accomplished with the Lambda-Sond sensor, commonly referred to as the exhaust gas oxygen sensor, or EGO sensor, or O2 sensor. This sensor resembled a spark plug without an electrode and is designed into the exhaust system upstream of the catalyst. The EGO sensor measures the oxygen content in the exhaust. Oxygen, or the lack of it, is proportional to the air/fuel mixture ingested into the engine.
"Closed loop feedback" fuel control made possible by digital EFI systems reduced exhaust emissions to less than 1% of the 1960 models. Unleaded fuel protects the catalytic converter so this level of emission performance is durable for tens of thousands of miles.
Starting in 1982, Bosch used a mass airflow meter on their L-Jetronic system, changing the name to LH-Jetronic (L for Luft, or air, and H for Heiße-leitung, or hot-wire), as the first true sensor for actual air mass involved the use of a heated platinum wire. The LH-Jetronic system is also notable in that it was the first system to abandon an analog ECU (using mainly AF components) in favor of a digital computer, which is now the prevailing form of ECU. This further refined air/fuel ratio control.
The introduction of microprocessor controls allowed the integration of fuel injection and ignition control, with systems first appearing in 1982 (The Bosch Motronic system, which oddly reverted to using a mechanical airflow sensor until the mid-to-late 1980s). Full engine management systems came shortly afterwards, with control of all engine systems under the control of a single computer. In 2005, many new cars had multiple computers on board controlling every aspect of the car.