U N I T 2 PRESENT TRENDS This Unit deals with some of the most important improvements concerning the internal combustion engine technology: fuel injection and supercharging systems. It also gives information on new types of alternative engines. A. FUEL-DELIVERY SYSTEMS For a long time gasoline internal combustion engines have employed carburettors to deliver the right amount of fuel-air mixture to the cylinders. Depending on the vehicle s technological progress, carburettors are almost completely replaced today by fuel injection systems. Fuel injection is a method for delivering and metering the fuel supply: a fuel injector exploits the pressure from a pump to spray an intermittent, timed and Fuel Injection Pump carefully measured quantity of fuel or fuelair mixture. Electronic fuel injection allows the engine s efficiency, power and fuel economy to be improved. It also provides better pollution control and lower exhaust emissions. Sensors placed in the vehicle continuously monitor the engine s performance, transmitting data to a computer system called the E.C.U. (electronic control unit). This controls and varies fuel supply, injection timing and air-fuel ratio according to the information received, regulating the engine s ignition system as well. Diesel engines employ either direct or indirect injection: in the first case, fuel is injected directly into the combustion chamber while in the second, it is conveyed into a smaller auxiliary chamber. Most petrol engines rely on indirect systems: one of the most common is the multi-port fuel injection (MFI), which includes a fuel injector for each cylinder, usually located so that it sprays right at the intake valve. Injectors GLOSSARY fuel injector: iniettore di combustibile 268 to meter: misurare, controllare (con un contatore) pollution: inquinamento