With the advancement in technology, motor vehicles have too gained in that; we now have a sort of computer onboard most vehicles manufactured from the year 2000 onwards. This has brought with it the increased fuel economy as well as reduction in pollution levels. For several decades, the internal combustion engine heavily relied on the carburettor to supply fuel to the engine. On many other machines, such as lawnmowers and chainsaws, that is still the case. But as the automobile evolved, the carburettor got more and more complex trying to handle all of the operating requirements. Some tasks had as many as five different circuits e.g. Main circuit - Provides just enough fuel for fuel-efficient cruising, Idle circuit - Provides just enough fuel to keep the engine idling, the accelerator pump Provides an extra burst of fuel when the accelerator pedal is first depressed, reducing hesitation before the engine speeds up , the Power enrichment circuit - Provides extra fuel when the car is going up a hill or towing a trailer, the Choke provides extra fuel when the engine is cold so that it will start, etc. In order to meet stricter emissions requirements, catalytic converters were introduced. Very careful control of the air-to-fuel ratio was required for the catalytic converter to be effective. Oxygen sensors monitor the amount of oxygen in the exhaust, and the engine control unit (ECU) uses this information to adjust the air-to-fuel ratio in real-time. This is called closed loop control it was not feasible to achieve this control with carburettors. There was a brief period of electrically controlled carburettors before fuel injection systems took over, but these electrical carburettors were even more complicated than the mechanical ones. At first, carburettors were replaced with throttle body fuel injection systems (also known as single point or central fuel injection systems) that incorporated electrically controlled fuel-injector valves into the throttle body. These were almost a bolt-in replacement for the carburettor, so the automakers didn’t have to make any drastic changes to their engine designs. With the onset of the computerised fuel injection, gradually, as new engines were designed, throttle body fuel injection was replaced by multi-port fuel injection (also known as port, multi-point or sequential fuel injection). These systems have a fuel injector for each cylinder, usually located so that they spray right at the intake valve. These systems provide more accurate fuel metering and quicker response. The gas pedal in your car is connected to the throttle valve this is the valve that regulates how much air enters the engine. So the accelerator pedal is actually the air pedal. When you step on the accelerator pedal, the throttle valve opens up more, letting in more air. The engine control unit (ECU, the computer that controls all of the electronic components on your engine) “sees” the throttle valve open and increases the fuel rate in anticipation of more air entering the engine. It is important to increase the fuel rate as soon as the throttle valve opens; otherwise, when the accelerator pedal is first pressed, there may be a hesitation as some air reaches the cylinders without enough fuel in it. eddie@afrowebs.com
