Working of Solex Carburetor

Q: Working at the Time of Starting

At the time of startings, a rich mixture is required by the engine. The Solex Carburetor is a starting circuit or bi-starter to provide a rich mixture at the time of starting.

Important Point

What Is Solex Carburetor?

Solex carburetor is invented by Marcel Mennesson and Maurice Goddard, founder of Solex company. Solex carburetors, widely used by many European makers, are also used in passenger cars and commercial vehicles. The Solex carburetor is a modification of an ordinary carburetor.

The ordinary carburetor works well under normal working conditions but does not work well in conditions such as winter and summer seasons, idle conditions, and high acceleration conditions. In these situations, the Solex carburetor works well.

The main function of the carburetors is to make the air-fuel mixture in the correct proportions. The Solex carburetor engine is known for its ease of starting and the engine’s superior performance. The Solex carburetor is a downdraught carburetor. In the downdraught carburetor, air enters from above and exits below.

The main drawback of the simples carburetor is that it cannot maintain different air-fuel mixtures for different driving conditions, but the Solex carburetor may provide different mixtures for different driving conditions. This variation in the air-fuel mixture for different conditions can be achieved using a Solex carburetor.

This Solex carburetor can provide a rich mixing engine start and a lean mixture when traveling at an economical speed with the vehicle. It can also provide different blends for different situations such as engine idling, low-speed operation, acceleration, etc.

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Construction of Solex Carburetor:

In the Solex carburetor, the fuel chamber is the part that collects fuel from the fuel tank and stores it in the carburetor to form an air-fuel mixture. This fuel chamber has a float which is used to maintain the fuel level in the fuel chamber. There is a mainline through which the fuel venturi reaches the throat tube. Fuel enters the venturi throat duct from the main jet, which is located at the end of the main line. The fuel from the main jet evaporates when the choke opens.

Fuel from the main jet is mixed with air that comes when the choke is opened to form an air-fuel mixture, and this air-fuel mixture reaches the engine cylinder when the throat valve is opened. Apart from the main jet, there’s are three more pipelines through which the engine cylinders get fuel; they are pilot jets, pump jets, and starting routes.

The pump jet gets fuel from the acceleration pump, and the pilot jet gets fuel from the main jet. The pilot jet’s pipeline is separated from the mainline. The acceleration pump operates using an acceleration pedal. These accelerations pumps are used during acceleration.

The pilot jet is used during the idle or no-loads condition. It has a pilot bleed orifice that allows the pilot jet to the air to form an air-fuel mixture. Near the end of the idle position pipeline, there is an idol screw used to control the amount of air-fuel mixture to pass into the engine cylinder.

The starting passage gets its fuel from the starting circuit or by the starter. These starting circuits are used to supply the air-fuel mixture during the initial time. This initial circuit consists of a flat disc with holes of different radius used to control the amount of fuel supply during starting.

This starting circuit also has an air venturi that supplies air to the starting circuit to create an air-fuel mixture. The air-fuel mixture from the starting circuit is supplied to the engine cylinder from the starting passage, which is present below the throttles valve.

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Working of Solex Carburetor:

Before the fuel chamber, the fuel enters the fuel chamber, which is blocked by afloat when the required amount of fuel enters the fuel chamber. The float that blocks the passage of the fuel tank and the fuel chamber raises the fuel level in the fuel chamber and blocks the passage when the fuel level reaches the maximum level in the fuel room.

#1. Working at the Time of Starting

At the time of starting, a rich mixture is required by the engine. The Solex Carburetor is a starting circuit or bi-starter to provide a rich mixture at the time of starting.

The main function of the by-starter is to compensate for the problem encountered while starting the engine, especially in the winter season.

This gives the engine a rich mix at the time of starting. The ratio of a rich mixture of air and fuel is 11: 1, where 11 parts are air and 1 part is fuel. Typically the fuel ratio expected by the engine is 15: 1, but it requires a ratio of 11: 1 to start at the time of starting. This bi-starter has a flat disc and has holes of different diameters.

The starter petrol jet & starter air jet are connected near the hole in the disc, and the air-fuel mixture reaches the engine in a suction stroke through the various holes in the starter disc.

Through these holes, the fuel & air pass from the Bi-Starter to the engine. This disc can be manually rotated using a starter lever so that it can be adjusted as per fuel and air requirements. For example, a larger hole in the disc would be used in winter because more fuel would be needed to start the engine in winter.

#2. Working During Idling & Slow Running of the Engine

Idling is a situation when the vehicle engine is running but not at Vehicle speed. This condition normally occurs when the red light turns off the vehicle, and the engine is powered on. In the idle state, there is no load on the engine, but all engine friction needs to be removed to keep the engines running.

During the idle position or slow running condition, the throttle valve is fully closed. Since the throttle valve is closed, the suctions created by the suction stroke is directly worked on the pilot jet. A pilot jet is a jet that receives its fuel from the mainline. The pilot jet pipes are connected to the mainline and provide fuel to it.

In the idle state, the throttle valve closes, and proper pressure is not created to suck fuel from the main jet. So the suction stroke of the engine directly sucks the air-fuel mixture from the pilot jet. The fuel from the pilot jet will be incorporated and mixed with the air sucked from the pilot air-bleed orphic from the outside environment.

The enriched mixture from the pilot jet will be sent directly to the engine by a tube located under the throttle valve.

A useless screw is present near the opening of the pilot jet to control the engine speed by controlling the amount of air-fuel mixture to the engine.

By-pass arrangements are also provided just above the throttle valve so that if the pressure is close enough to the throttle valve to suck the air-fuel mixture from the pass-through arrangement. The throttle valve will open slightly when this near-by arrangement is used.

A less enriched air-fuel mixture will be provided by the by-pass arrangement so that the engine can run smoothly with full movement of the air-fuel mixture. The idle running position works at a speed of 0 to 30 (KMPH), and after that, it stops automatically.

#3. Working During Acceleration

During acceleration, a load occurs on the engine. Additional air-fuel mixing is required by the engine during acceleration to give the engine proper acceleration. An additional acceleration pump injector is provided to the right of the float chamber to provide the additional air-fuel mixture required during acceleration.

An additional jet is provided on top of the main jet to supply the additional fuel supplied using the acceleration pump. This acceleration pump is a diaphragm pump that is connected to a pedal. It is also connected to the throttle valve via an acceleration pedal linkage.

When we press the acceleration pedal, the acceleration pump will operate, and at the same time, the throttle valve will open simultaneously. As soon as the acceleration pedals are pressed, the acceleration pump will operate and provide additional fuel through the extra jet.

When the acceleration pedals are released, the acceleration pump will soak up the fuel from the fuel chamber and store it to provide additional fuel for the next acceleration.

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Types of Solex Carburetor:

Solex carburetors are classified into three main categories.

By its type,
The bore of the throttle chamber and
By its model.

The Solex carburetor is classified according to the direction of flow through the carburetor.

Updatable Carburetor.
Horizontal Carburetor.
Downdraught Carburetor.

According to the layout of the inductions system

Simple carburetor for single induction manifold.
Dual Port Carburetor for two induction manifolds.
Dual-port compound carburetor for the single-induction manifold.

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Selection of Solex Carburetor:

#1. The Direction of Air Flow

If you want to replaces an old carburetor with a new one, this is easily done by determining the flange type of the carburetor. In modern vehicles, downdraught carburetor is commonly used, as it is easily accessible from all sides.

In sports cars and racing cars, horizontal carburetors are used. Updraught carburetors are used for engines where fuel is fed.

#2. The Number of Carburetor

Typically, this is determined by the type of engine, whether one or more carburetors are used. Typically, in sports cars & racing cars, more than one carburetor is used. The purpose of using multiples carburetors is to reduce the length of the induction manifold. And most importantly, reducing bends that impede the free passage of the air–fuel mixture.

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Advantages of Solex Carburetor:

Here, the different advantages of the Solex carburetor are as follows.

All circuits work differently for different situations.
It reduces waste and reduces carbon formation.
Throttle response is higher than another carburetor.
It works perfectly under suddens heavy acceleration requirements.
It starts very easily.

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Frequently Asked Questions (FAQ)

Solex Carburetor

Solex is a French manufacturer of carburetors and VéloSoleX bikes. Solex H30 was installed in a 1970 Volkswagen. Solex carburetors were used by many European car companies and licensed to Japanese manufacturer Mikuni.

Solex Carburetor Types