Some models of Solex carburettor have been manufactured in India (under licence) by M/s carburettor Limited, Madras. Solex carburettor model M.34 PBIC, used in Willlys jeep (CJ-3B and 475-4WD engines). down drought type of carburettor, with special provision for a progressive starter, which supplies richer mixture for starting and then gradually weakens it till the engine has reached its normal operating temperature.
Starting:
The starter valve is in form of a flat disc with holes of different sizes. These holes connect the petrol jet and starter jet sides to the passage which opens into the air horn just below the throttle valve. Depending upon the position of the starter lever, which can be adjusted by the driver on the dash board, either bigger or smaller holes come opposite the passage. Initially for starting richer mixture is required and after the engine starts the richness required decreases. So in the start position, bigger holes are the connecting holes. The throttle valve being in the closed position, the whole of the engine suction is applied to the starting passage 1 due to which the petrol from the float chamber passes through the starter petrol jet and rises into passage 2,
some of it comes out, and mixes with the air entering through the air jet. The jets and passages are so shaped that mixture so supplied to the carburettor is rich enough for starting.
After the engine has started, the starter lever is brought to the second position, in between the initial and final positions. Now the smaller holes in the valve complete the circuit, thus reducing the amount of petrol. Also in this position, the throttle valve is partly open, so that the petrol is also coming out from the main jet. The reduced mixture supply from the starter system in this situation is however sufficient to keep the engine running, till it reaches the normal running temperature, when the starter is brought to ‘off’ position.
2. Idling or low speed operation
An idle port controlled by idle adjusting screw is provided in the engine
side of throttle valve. As the throttle is almost closed the engine suction is
applied at the pilot petrol jet, which supplies petrol. The jet itself draws
petrol from the main jet circuit. The air is drawn in from the pilot air jet. The
petrol and the air mix in the idle passage and the mixture comes out of the idle port.
To ensure the smooth transfer from idle and low speed circuit to the main jet
circuit without the occurrence of flat spot, slow running openings are provided on the venturi side of throttle valve. As the throttle is opened wide, the suction at idle port is decreased. But suction is also applied now at the slow speed openings, which more than offsets the loss of suction at the idle port and thus flat spot is avoided.
Normal running
The throttle is held partly open, so that the engine suction is now applied the main jet, which now supplies fuel. The air enters directly through the venturi, the quantity of mixture being governed with the throttle valve.
Acceleration
To avoid ‘flat spot’ during acceleration, a separate membrane pump is provided, which delivers spurts of extra needed fuel for acceleration. Pump lever is connected to the accelerator pedal so that when the same is pressed, the lever moves towards left, thus pressing the membrane towards left and forcing petrol into main jet circuit. when the pedal is left free, the lever moves the membrane back towards right creating vacuum towards left which opens the ball valve provided and thus admits the petrol from chamber into the pump itself.
SOLEX MIKUNI DOUBLE VENTURI CARBURETTOR
This type of carburettor is used in Maruti 800 car. Its main components are primary and secondary venturis, float chamber, acceleration pump, a fuel cut solenoid valve and a depression chamber to actuate the secondary throttle valve. choke valve is provided in the primary air horn only. various circuits of the carburettor are discussed here.
1. Idle and slow speed circuit
The fuel from the float chamber flows through main jet l and reaches slow jet 2, where it is metered and mixed with-air, the air being already metered at slow air holes no. 6 and 7. This air-fuel mixture is sprayed out through bypass port 3 and idle port 4. During idling the mixture flows through mainly the idle port. The quality of this mixture can be controlled by means of the idle adjustment screw.
2. High speed circuit (primary)
when the accelerator pedal is pressed from the idling stage to open the primary throttle valve, the fuel from the float chamber is metered from the main jet 1 and enters the bleed pipe 10. The air is metered at primary main air holes 11 and 12 and the air-fuel mixture comes out through the main nozzle into the primary venturi 13.
3. High speed circuit (secondary)
In this circuit the major part is played by a depression chamber 17 which
consists of a diaphragm 18, one side of which is exposed to atmospheric pressure, while the other side is connected to hole 16. The diaphragm is connected to the secondary throttle valve through a rod and a lever. When the primary throttle 14 is opened wider, i.e., about 40o or more, the vacuum from engine inlet manifold is applied to the primary venturi and
is further transmitted through hole 16 to the depression chamber where it causes the diaphragm to be pulled up thus opening the secondary throttle valve. Now the fuel from the secondary main jet 19 reaches the secondary pilot jet 20 and the air metered at secondary pilot air hole 21 mixes with it. This air-fuel mixture is sprayed out of the by-pass port 22. when the vacuum in the primary venturi is increased and the same goes to the secondary venturi also, the secondary throttle valve is opened further. Then the fuel from main jet 19 and the air from the secondary main air hole 23 are mixed in bleed pipe 24 and this mixture is sprayed out through the secondary main nozzle into the secondary venturi.
4. Acceleration power
when the throttle is opened suddenly for acceleration, while the engine
is idling or is running at slow speed, a device is needed to make the carburettor respond without delay. Such a device in this carburettor is provided in the from of a membrane type acceleration pump. The operating lever of this pump is connected to the shaft of the primary throttle valve. When the acceleration pedal is depressed for acceleration, the pump lever pushes the diaphragm forcing fuel out of pump nozzle into the primary venturi. When the accelerator pedal is released the diaphragm is brought back to the original position by the spring, the discharge ball valve is closed and the inlet valve is opened admitting fuel in the pump chamber.
Solenoid valve
when the ignition key is turned off, the engine does not stop immediately with the result that in the absence of some special device, the carburettor would continue to deliver the air fuel mixture through the idling and slow speed circuit, till the engine stops. such a run-on of the engine is prevented in the Solex Mikuni carburettor by means of a solenoid valve. It operates a needle valve which opens or closes the passage for idling and slow speed circuit. when the ignition key is ON, current flows in the solenoid coil generating the magnetic force, which pulls the needle valve so as to open the passage. However, when the ignition key is turned OFF, the magnetic force disappears and the spring in the solenoid valve brings back the needle valve to its original position when it cuts-off the slow speed passage, thus preventing engine run-on.01) Starting
Circuit:-
The throttle valve remains in closed position during starting.The petrol is supplied to the starter petrol jet through first passage from the float chamber and
the air through the starter air jet for starting operation.
Starting Valve which have different sizes hole,is made from flat disc.The position of various holes can be adjusted in front of starter petrol jet by starter lever and then air is mixed coming from starter air jet .This air-fuel mixture,passes through another holes of starter valve,in a passage of the carburettor,below the throttle valve.The suction stroke of the engine sucks this mixture into the cylinder.This mixture is rich enough to start the engine.After the engine starts and speed increases,a weak mixture is required,therefore,a small hole of the starter valve is brought in front of the starter petrol jet by means of starter lever,there by reducing the quantity of petrol,which weaken the air-fuel mixture.Similarly next smaller hole of the starter valve is brought in front of starter petrol jet till the engine attains its normal speed then the starter valve is closed by bringing the starter lever to its off position.
Normal Running Circuit:-
At normal running speed,starting circuit is closed and throttle valve is opened.The normal running circuit consist of main jet which receives the petrol through second passage,from the float chamber as the throttle valve is opened sufficiently,the air is drawn through the venturi where the petrol mixes up with it forming a suitable mixture for the normal running of the engine.In this case,only throttle valve,governed the air-fuel ratio.
Accelerating Circuit:-
The engine requires an extra rich mixture,during acceleration period.To obtained extra rich mixture,the fuel is pumped under pressure into the main air passage or in the venturi through an injector. Diaphragm pump is used to create pressure,which is actuated by a lever connected to the accelerator.The pump sucks the petrol from the float chamber through the pump valve and forces it through third passage into the main passage through an injector above the venturi of the carburettor.
Idling And Slow Running Circuit:-
During the idling operation,the throttle valve is kept closed and the engine receives the mixture through a port opening below the throttle valve,whose area can be varied by an idle adjusting screw according to the need of the engine.The petrol is supplied to a pilot petrol jet from the main jet fuel circuit through fourth passage and the air from a pilot air jet .The petrol and air thus supplied mix up in the idle passage and go to a port situated below the throttle valve from where the mixture is sucked by engine. During the slow running,the engine draws the mixture from the idle passage through a hole situated above the throttle valve when the throttle valve is
partially opened.
Starting:
The starter valve is in form of a flat disc with holes of different sizes. These holes connect the petrol jet and starter jet sides to the passage which opens into the air horn just below the throttle valve. Depending upon the position of the starter lever, which can be adjusted by the driver on the dash board, either bigger or smaller holes come opposite the passage. Initially for starting richer mixture is required and after the engine starts the richness required decreases. So in the start position, bigger holes are the connecting holes. The throttle valve being in the closed position, the whole of the engine suction is applied to the starting passage 1 due to which the petrol from the float chamber passes through the starter petrol jet and rises into passage 2,
some of it comes out, and mixes with the air entering through the air jet. The jets and passages are so shaped that mixture so supplied to the carburettor is rich enough for starting.
After the engine has started, the starter lever is brought to the second position, in between the initial and final positions. Now the smaller holes in the valve complete the circuit, thus reducing the amount of petrol. Also in this position, the throttle valve is partly open, so that the petrol is also coming out from the main jet. The reduced mixture supply from the starter system in this situation is however sufficient to keep the engine running, till it reaches the normal running temperature, when the starter is brought to ‘off’ position.
2. Idling or low speed operation
An idle port controlled by idle adjusting screw is provided in the engine
side of throttle valve. As the throttle is almost closed the engine suction is
applied at the pilot petrol jet, which supplies petrol. The jet itself draws
petrol from the main jet circuit. The air is drawn in from the pilot air jet. The
petrol and the air mix in the idle passage and the mixture comes out of the idle port.
To ensure the smooth transfer from idle and low speed circuit to the main jet
circuit without the occurrence of flat spot, slow running openings are provided on the venturi side of throttle valve. As the throttle is opened wide, the suction at idle port is decreased. But suction is also applied now at the slow speed openings, which more than offsets the loss of suction at the idle port and thus flat spot is avoided.
Normal running
The throttle is held partly open, so that the engine suction is now applied the main jet, which now supplies fuel. The air enters directly through the venturi, the quantity of mixture being governed with the throttle valve.
Acceleration
To avoid ‘flat spot’ during acceleration, a separate membrane pump is provided, which delivers spurts of extra needed fuel for acceleration. Pump lever is connected to the accelerator pedal so that when the same is pressed, the lever moves towards left, thus pressing the membrane towards left and forcing petrol into main jet circuit. when the pedal is left free, the lever moves the membrane back towards right creating vacuum towards left which opens the ball valve provided and thus admits the petrol from chamber into the pump itself.
SOLEX MIKUNI DOUBLE VENTURI CARBURETTOR
This type of carburettor is used in Maruti 800 car. Its main components are primary and secondary venturis, float chamber, acceleration pump, a fuel cut solenoid valve and a depression chamber to actuate the secondary throttle valve. choke valve is provided in the primary air horn only. various circuits of the carburettor are discussed here.
1. Idle and slow speed circuit
The fuel from the float chamber flows through main jet l and reaches slow jet 2, where it is metered and mixed with-air, the air being already metered at slow air holes no. 6 and 7. This air-fuel mixture is sprayed out through bypass port 3 and idle port 4. During idling the mixture flows through mainly the idle port. The quality of this mixture can be controlled by means of the idle adjustment screw.
2. High speed circuit (primary)
when the accelerator pedal is pressed from the idling stage to open the primary throttle valve, the fuel from the float chamber is metered from the main jet 1 and enters the bleed pipe 10. The air is metered at primary main air holes 11 and 12 and the air-fuel mixture comes out through the main nozzle into the primary venturi 13.
3. High speed circuit (secondary)
In this circuit the major part is played by a depression chamber 17 which
consists of a diaphragm 18, one side of which is exposed to atmospheric pressure, while the other side is connected to hole 16. The diaphragm is connected to the secondary throttle valve through a rod and a lever. When the primary throttle 14 is opened wider, i.e., about 40o or more, the vacuum from engine inlet manifold is applied to the primary venturi and
is further transmitted through hole 16 to the depression chamber where it causes the diaphragm to be pulled up thus opening the secondary throttle valve. Now the fuel from the secondary main jet 19 reaches the secondary pilot jet 20 and the air metered at secondary pilot air hole 21 mixes with it. This air-fuel mixture is sprayed out of the by-pass port 22. when the vacuum in the primary venturi is increased and the same goes to the secondary venturi also, the secondary throttle valve is opened further. Then the fuel from main jet 19 and the air from the secondary main air hole 23 are mixed in bleed pipe 24 and this mixture is sprayed out through the secondary main nozzle into the secondary venturi.
4. Acceleration power
when the throttle is opened suddenly for acceleration, while the engine
is idling or is running at slow speed, a device is needed to make the carburettor respond without delay. Such a device in this carburettor is provided in the from of a membrane type acceleration pump. The operating lever of this pump is connected to the shaft of the primary throttle valve. When the acceleration pedal is depressed for acceleration, the pump lever pushes the diaphragm forcing fuel out of pump nozzle into the primary venturi. When the accelerator pedal is released the diaphragm is brought back to the original position by the spring, the discharge ball valve is closed and the inlet valve is opened admitting fuel in the pump chamber.
Solenoid valve
when the ignition key is turned off, the engine does not stop immediately with the result that in the absence of some special device, the carburettor would continue to deliver the air fuel mixture through the idling and slow speed circuit, till the engine stops. such a run-on of the engine is prevented in the Solex Mikuni carburettor by means of a solenoid valve. It operates a needle valve which opens or closes the passage for idling and slow speed circuit. when the ignition key is ON, current flows in the solenoid coil generating the magnetic force, which pulls the needle valve so as to open the passage. However, when the ignition key is turned OFF, the magnetic force disappears and the spring in the solenoid valve brings back the needle valve to its original position when it cuts-off the slow speed passage, thus preventing engine run-on.01) Starting
Circuit:-
The throttle valve remains in closed position during starting.The petrol is supplied to the starter petrol jet through first passage from the float chamber and
the air through the starter air jet for starting operation.
Starting Valve which have different sizes hole,is made from flat disc.The position of various holes can be adjusted in front of starter petrol jet by starter lever and then air is mixed coming from starter air jet .This air-fuel mixture,passes through another holes of starter valve,in a passage of the carburettor,below the throttle valve.The suction stroke of the engine sucks this mixture into the cylinder.This mixture is rich enough to start the engine.After the engine starts and speed increases,a weak mixture is required,therefore,a small hole of the starter valve is brought in front of the starter petrol jet by means of starter lever,there by reducing the quantity of petrol,which weaken the air-fuel mixture.Similarly next smaller hole of the starter valve is brought in front of starter petrol jet till the engine attains its normal speed then the starter valve is closed by bringing the starter lever to its off position.
Normal Running Circuit:-
At normal running speed,starting circuit is closed and throttle valve is opened.The normal running circuit consist of main jet which receives the petrol through second passage,from the float chamber as the throttle valve is opened sufficiently,the air is drawn through the venturi where the petrol mixes up with it forming a suitable mixture for the normal running of the engine.In this case,only throttle valve,governed the air-fuel ratio.
Accelerating Circuit:-
The engine requires an extra rich mixture,during acceleration period.To obtained extra rich mixture,the fuel is pumped under pressure into the main air passage or in the venturi through an injector. Diaphragm pump is used to create pressure,which is actuated by a lever connected to the accelerator.The pump sucks the petrol from the float chamber through the pump valve and forces it through third passage into the main passage through an injector above the venturi of the carburettor.
Idling And Slow Running Circuit:-
During the idling operation,the throttle valve is kept closed and the engine receives the mixture through a port opening below the throttle valve,whose area can be varied by an idle adjusting screw according to the need of the engine.The petrol is supplied to a pilot petrol jet from the main jet fuel circuit through fourth passage and the air from a pilot air jet .The petrol and air thus supplied mix up in the idle passage and go to a port situated below the throttle valve from where the mixture is sucked by engine. During the slow running,the engine draws the mixture from the idle passage through a hole situated above the throttle valve when the throttle valve is
partially opened.
1 comments:
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