A carburettor is a part of a petrol engine whose job is to mix petrol with air in the right amounts so the mix can burn and give the engine power. Think of it as a careful blender on the way in: too little air and the mix is too rich; too little petrol and it is too weak; the carburettor tries to get that balance. This spelling (two t’s, -our) is the British one. American English writes carburetor — same object, different letters. Though actually, most modern cars no longer have one. They use fuel injection, which sprays petrol in a more tightly controlled way. You still meet carburettors on some scooters, lawn mowers, generators, and older cars. In a garage people often just use the Chinese name. It sits on the intake side of the engine. It is not the box that cleans the waste gas on the way out.

化油器（美式拼法 carburetor 是同一零件）