Fuel injection quietly killed the carburettor after a century of experiments
A carburettor lets rushing air suck fuel into the engine. Fuel injection does the opposite, forcing fuel through a tiny nozzle under high pressure to atomise it. The idea dates to 1872, but petrol cars only fully abandoned carburettors by the early 1990s.
The term covers many different designs; the one thing they share is the absence of a carburettor. Every system needs a pump to pressurise fuel, a way to work out how much fuel to deliver, and an injector, essentially a spray nozzle, placed in the combustion chamber, the intake manifold or occasionally the throttle body. Mechanical systems once used intricate helix-controlled pumps; since the 1980s electronics have handled metering, and modern engine control units also set ignition timing.
The big divide is where fuel meets air. In direct injection, only air enters on the intake stroke and fuel is sprayed straight into each cylinder; the most common modern form is common rail, where a high-pressure accumulator feeds injectors opened by solenoid valves, or piezoelectric ones in later diesels. Manifold injection mixes fuel and air outside the cylinder, either at each intake port or through a single injector in a throttle body. That cheaper single-point approach helped carmakers meet emissions rules, and in America it lasted until the 2000 Chevrolet Metro.
The history is long. George Bailey Brayton patented an engine with air-blast injection in 1872, and Rudolf Diesel borrowed and improved it in 1894, raising the blast pressure more than tenfold. Johannes Spiel designed the first manifold system in 1884, and the British Herbert-Akroyd oil engine of 1891 first used pressurised injection with a jerk pump. In 1919 Prosper l'Orange invented the pre-combustion chamber, making diesels small enough for vehicles. The first direct-injection petrol engine was a 1916 aircraft engine by Otto Mader, and the 1906 Antoinette, the world's first V8, used manifold injection.
Diesel cars came first. The Mercedes-Benz OM 138 of 1936 was among the first fuel-injected engines in a mass-produced passenger car. Second World War aircraft engines such as the Daimler-Benz DB 601 used direct petrol injection, petrol cars began adopting injection in the early 1950s, and Bosch's continuous K-Jetronic, launched in 1974, stayed in use until the mid-1990s.
Source: Fuel injection
