Carburateurs

Carburateurs, or carburetors in English, are devices that blend air and fuel for internal combustion engines. They regulate the fuel–air ratio as the engine operates, metering fuel from a float-chamber into the incoming air stream.

In a typical float-type carburetor, air enters through an intake and passes through a venturi. The constriction lowers air pressure and draws fuel through jets from the float bowl, where the fuel level is controlled by a needle valve. The throttle plate governs airflow and, thus, the mixture. A choke plate may enrich the mixture for cold starts. Additional circuits supply fuel at idle, mid-range, and high speed; accelerator pumps can provide a quick fuel surge when the throttle is opened.

Carburateurs vary in form: updraft, downdraft, and sidedraft layouts; single- to multi-barrel designs with primary and secondary circuits. Some designs use constant-velocity metering or automatic enrichment valves.

Applications and decline: Because electronic fuel injection offers better efficiency and emissions control, carburetors were largely replaced in modern passenger cars during the late 20th century. They remain common on many small engines (lawn mowers, generators), motorcycles, and vintage vehicles, as well as some light aircraft.

Maintenance and issues: Carburetors require periodic cleaning to remove varnish from old fuel, adjustment of idle and mixture settings, and synchronization of multiple barrels. Problems include flooding, icing, leaks, and fuel starvation due to clogged jets or improper float height. Rebuild kits and specialized cleaners are used for maintenance.