Carburetor — General Description (Opel Vectra A)

1. Carburetor Pierburg 2E3 - two-chamber, with fixed jets and a sequential throttle valve. Only one primary throttle valve operates (except at high engine speed and high load conditions, when the secondary throttle valve begins to be used) to full throttle, when both valves are fully open. This design provides good fuel economy during light acceleration and smooth cruising, and provides maximum power at full throttle. The secondary throttle valve is vacuum-controlled, depending on the vacuum in the primary throttle body. The primary throttle body and throttle body diameters are smaller than the secondary ones. The carburetor is a complex device that has many subsystems designed to improve overall vehicle handling, fuel economy, and emissions (see illustrations).







2. The idle system operates independently of the main jet system and is controlled by the mixture adjustment screw.



3. The main jets are calibrated to allow the engine to operate normally at half throttle. To ensure the required amount of fuel at full throttle, a vacuum economizer valve is used. The valve supplies additional fuel at low pressure, at fully open throttles.

4. To enrich the mixture during acceleration, the accelerator pump supplies additional fuel to the primary main diffuser. The accelerator pump is mechanically controlled by a cam from the throttle linkage.

5. The system uses a fully automatic air damper, controlled by a cooling and electrically heated bimetallic spring. When the engine is cold, the bimetallic spring is fully wound, holding the damper in place (in the primary chamber) in the closed position. As the engine warms up, the bimetallic spring heats up and unfolds, gradually opening the valve. The vacuum controls the pull-down system, as a result of which, if the engine operates in a mode with the valve almost closed, but only with uniform movement (i.e. under light load), the valve is open against the bimetallic spring. The pull-down system prevents over-enrichment of the mixture (due to over-enrichment of the mixture, fuel consumption increases and wear of the cold engine increases). The secondary pull-down winding is used in combination with the main diaphragm unit to modify the pull-down characteristics and improve fuel economy.

6. The 1.8 litre models are equipped with an idle cut-off valve. This is an electrically controlled valve that cuts the idle mixture circuit when the ignition is switched off.