Three types of carburetor are used on Subaru vehicles. All 1.2L engines use a DFC-328 carburetor; 1.6L engines use a DCP-306 carburetor and 1.8L engines use a DCZ-328 carburetor.
The carburetor supplies the correct mixture of fuel and air to the engine under varying conditions. Despite their complexity in design, carburetors function because of a simple physical principle (the venturi principle). Air is drawn into the engine by the pumping action of the pistons. As air enters the top of the carburetor it passes through a venturi, which is nothing more than a restriction in the throttle bore. The air speeds up as it passes through the venturi, causing a slight drop in pressure. The pressure drop pulls fuel from the float bowl through a nozzle into the throttle bore, where it mixes with the air and forms a fine mist which is distributed to the cylinders through the intake manifold.
The carburetor uses a progressive linkage between the primary and secondary circuit. For optimum performance plus fuel economy, the secondary circuit of the carburetor is used only at high engine rpm. Normal low speed operation is handled by the primary circuit.
On later models, the carburetor is provided with a coasting bypass system which helps control exhaust emissions during deceleration.
An automatic control choke is used on all carburetors. The automatic choke and a throttle chamber are heated by engine coolant to prevent throttle bore icing, help the engine start and run well in the coldest conditions.
The basic systems of the carburetor are:
NOTE: If you are planning to clean, rebuild or replace your carburetor, be sure you understand what is necessary. Read all instructions, have all parts and tools on hand and keep everything as clean as possible. Remember that gasoline mileage and performance depend on how well you do the job.