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What is Zenith Carburetor – Diagram and Working

Introduction To Carburetor :

Carburetor is a device used for atomizing and vapourizing the fuel and mixing it with the air in varying proportions to suit for changing the operating conditions of engines. The process of breaking up and mixing the fuel with the air is called carburetion. The term vapourization and atomization should be understood clearly. Vaporization is a change of state of the fuel from liquid to vapour whereas atomization is a mechanical breaking-up of the liquid into small particles so that every minute particle of the fuel is surrounded by the air.
The carburetor is supposed to supply the fuel air mixture in correct proportion under different conditions of temperature, speed and load on engine. Relatively rich mixture of air fuel ratio of 12:1 is required by the engine while accelerating or running at high speeds. A leaner mixture of air-fuel ratio of 16:1 is sufficient while running on levelled roads. For idling, a richer mixture of about 14:I is needed. Similarly, an extremely rich mixture having a ratio of 9:1 is required during cold starting.

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What is Zenith Carburetor

Zenith carburetor is quite popular with England cars and is available in different form and models. Few such models are given below.

(i) Zenith VE type carburetor
(ii) Zenith Stromberg carburetor
(iii) Zenith 30 VIGII carburetor
(iv) Zenith NV type carburetor
(v) Zenith DBE type carburetor
(vi) Zenith WIA type carburetor etc.

Instead of employing two side by side jets in other types, a compound jet consists of an inner main jet and a concentric outer jet is used in this carburetor. It is most popular due to its easy starting, slow running, better economy as well as simple to adjust and requiring no
adjustment once set. A standard model of a Zenith carburetor is shown in Figure 2.23. It is an old type of Zenith carburetor but in modem Zenith carburetors, economy devices as well as accelerating pumps are also provided.

It consists of three jets namely, main jet, compensating jet and idling jet. An outer cover is provided for the main jet. The annular space between main jet and outer cover forms the delivery tube for compensating jet. A choke is used for starting. For idling and slow speed running, a throttle valve is closed and the air enters through holes A and B which mixes with the fuel in idling passage and then the mixture passes to the idling jet. A knob is provided for idle adjustment which controls the opening of B. It affects the air intake in B and thus, the quality of mixture is controlled. When the throttle is opened slightly, some air will flow through venturi. The fuel mixture would be
supplied by both main jet and slow running jet.

When the throttle is opened further, the depression at the slow running jet will be destroyed. The whole of the suction is being applied at the main and compensating jets. A direct air fuel ratio at different speed is maintained by a compensating jet. In this carburetor, a provision is also made for collecting any sediment or dirt entering with the petrol.