Chevrolet Corvette Stingray concept car 2009

Chevrolet Corvette Stingray concept car 2009
General Motors used the Chicago Auto Show to introduce the world to its latest concept vehicle, the Corvette Stingray, which will be featured in the upcoming Transformers: Revenge of the Fallen movie on June 26th. According to GM, the vehicle is nothing more than a styling buck that was influenced by the original 1959 Stingray racer when it was spotted by director Michael Bay while he was touring GM's operations looking for inspiration for the first Transformers movie. Don't expect this concept to spawn any sort of production vehicle, which, needless to say, is a shame. In robot mode, the Corvette Stingray Concept will take the form of Sideswipe, who will reportedly be a skater with wheels for feet. The General doesn't have anything in the way of new product to show off here in Chicago, so it's using the blockbuster movie to drum up interest instead. It's working... sorta. BUMBLEBEE™, the heroic AUTOBOT based on Chevrolet’s Camaro concept from the first “Transformers” movie, returns with a high-performance attitude. Joining the vehicles on stage will be BUMBLEBEE in his AUTOBOT form, standing almost 17 feet (5.2 meters) tall and 13 feet (4 meters) wide.

“Chevrolet is thrilled to again be part of one of the most anticipated movies in years,” said Ed Peper, GM North America vice president, Chevrolet. “‘Transformers’ gives us a great opportunity to connect with young people on their terms, with a dynamic, environmentally friendly image. The new characters represent the change going on in Chevy showrooms. From the exciting Camaro, the 21st century sports car, to the game-changing Volt, there’s more than meets the eye at Chevrolet today.”

Directed by Michael Bay, “Transformers: Revenge of the Fallen” sees the AUTOBOTS confront a new threat from DECEPTICONS® bent on avenging their earlier defeat on Earth. The new AUTOBOT characters in their current Chevy-based form square off against new, tougher foes determined to rule the universe.

“‘Transformers: Revenge of the Fallen’ goes way beyond the first film in terms of robot action and excitement,” said LeeAnne Stables, executive vice president of worldwide marketing partnerships at Paramount Pictures, the distributor of the film. “The new AUTOBOTS add to the storytelling, and these Chevy vehicles went with our filmmakers to locations all around the world. GM has again provided incredible support to the production team working on the movie.” SIDESWIPE represents an exercise in exploration for the Corvette,” said Ed Welburn, vice president of GM Global Design. “By giving my creative team the freedom to design no-holds-barred vision concepts, it helps them push boundaries and look at projects from different perspectives.” The Beat and Trax-based characters, SKIDS and MUDFLAP, remain faithful to their concept designs introduced at the 2007 New York Auto Show – although each wears new paint and other exterior accessories. And while they may be small cars, when they turn into fighting AUTOBOTS®, they pack a big punch.

The other new AUTOBOT, JOLT, appears in the production form of Chevy's 2011 Volt extended-range electric vehicle. With the capability of up to 40 miles (64 km) of pure electric propulsion, plus hundreds of more miles with the assistance from its Voltec powertrain system, the real-life Volt will change driving in America. Chevrolet is one of America's best-known and best-selling automotive brands. With the largest dealer network in the United States, Chevy is the leader in full-size trucks and the leader in sales of vehicles priced $35,000 and above. Chevrolet delivers more-than-expected value in every vehicle category, offering cars and trucks priced from $12,120 to $103,300. Chevy delivers expressive design, spirited performance and great value with standard features usually found only on more expensive vehicles. More information on Chevrolet can be found at www.chevrolet.com.

Maruti Suzuki Ritz 2009

Maruti Suzuki Ritz

Maruti Suzuki India Ltd. unveiled the much awaited Ritz which would be available both in petrol as well as diesel variants. Ritz is a tallboy hatchback, positioned in the premium A2 market segment Maruti Suzuki currently acquires 58% market share in the segment. Ritz is a first passenger car in India to be compliant with the BS-IV and OBD-I norms. The Maruti Suzuki Ritz adopts a contemporary European design and is positioned at the growing premium-end of the compact car market. With the launch of the vehicle, the company now consolidates its leadership in the highly competitive compact car segment.
It is built on a wheelbase smaller than the Swift but thanks to its cabin architecture and interior packaging, the upright seating stance delivers great space and headroom for four adults which is the mantra specified for a large hatch. With a 500-litres plus boot space, it is no slouch in the luggage packing detail which is where many of our countrymen try to hold out against large hatchbacks vis-a-vis saloons and this is the first such car in the segment which has got this point absolutely spot-on. Factor in a very well laid out funky interior (both in design as well as in the colour coded graphics and upholstery patterns employed), you get a car which has a good driving position (could have done with some adjustability though to driver's seat) and very good all-round visibility. Ample space for odds and ends abounds all across the interior and though the hard plastics at some places do show that it is built to a price, the overall ambience is of a pretty tall order. After the Skoda Fabia at the top end of the large hatch spectrum and the Tata Indica Vista on the same level, the Suzuki Ritz is probably the most important large hatch after these two to offer a choice of either petrol or diesel propulsion. The Ritz with its new K12 1197cc four-cylinder petrol engine is the first such to be BS IV compliant months before this emission level is mandatory. The oil burner option is taken care of by the very same and highly acclaimed 1.3-litre DDIS unit which does duty in the Swift as well as the Swift D'Zire. Together these two units offer a good choice to buyers in this category and for once we could say that the petrol would seem to be the more sensible choice. After Delhi and Bangalore, Maruti Suzuki India Ltd. unveiled its new car Ritz in Kolkata. However, Ritz is developed along the line of Maruti Suzuki's popular A2 model Swift. Maruti Suzuki has spent 40,000 million on developing Ritz. Five variants of the car-three in petrol and two in diesel-will be produced at the company's Gurgaon plant. The car, available both with petrol and diesel engines, comes with BS-IV and OBD-I compliance much ahead of the regulation being enforced in the country. Stylistically the car is surely the best ever "tall boy" design seen in this country and if looks alone could determine it as a winner, the Ritz could be galloping to the head of the pack on first eye contact. That it bolsters this attribute with performance, good ride quality, decent build and hopefully value-for-money, would just be added impetus for buyers wanting a big hatch without the encumbrance of a boot.


Variant and Pricing:-
Variant FuelType Price (Ex Showroom, Delhi)
Maruti Suzuki Ritz Lxi Petrol Rs.3,90,000/-
Maruti Suzuki Ritz Vxi Petrol Rs.4,20,000/-
Maruti Suzuki Ritz Zxi Petrol Rs.4.80,000/-
Maruti Suzuki Ritz Ldi Diesel Rs.4,65,000/-
Maruti Suzuki Ritz Vdi Diesel Rs.4,99,000/-

Honda FCX 2009

TORRANCE, Calif., U.S.A., April 9, 2009 - Recognizing Honda's commitment to environmental leadership in the area of alternative fuels and hydrogen-powered fuel cell technology, the Honda FCX Clarity was declared the 2009 World Green Car, American Honda Motor Co., Inc., announced.

The Zero-Emission Sedan of the Future

Zero emissions

Domestic fuel

Helps slow increase in greenhouse gases

Performance

The novel four-wheel-drive system has one front 80-kW electric motor with two in-wheel,

25-kw motors at the rear.

Fun to drive

Smooth and powerful

Groundbreaking new fuel cell stack

Safety

Six airbags

Vehicle Stability Assist™ (VSA®)

Collision Mitigation Braking System™ (CMBS™)

Manufacturer Honda Also called Honda FCX Production 2008–present Class mid-size Body style(s) 4-door sedan Layout FF layout Engine(s) electric motor Wheelbase 110.2 in (2799 mm) Length 190.3 in (4834 mm) Width 72.7 in (1847 mm) Height 57.8 in (1468 mm) Curb weight 3,528 lb (1,600 kg) Related Honda Insight (2nd Generation)

"The FCX Clarity is a symbol of the progress we have made with fuel cell vehicles and our commitment to developing vehicles that promote renewable energy supplies and zero-emissions transportation," said Steve Center, vice president, national Marketing Operations for American Honda.

The FCX Clarity, a sleekly styled hydrogen fuel cell-powered sedan currently available on a limited lease-basis, is propelled by an electric motor that runs on electricity generated by an on-board fuel cell stack. The vehicle's only emission is water, and its fuel efficiency is up to three times that of a modern gasoline-powered automobile and two times that of a gasoline-powered hybrid vehicle.

The most distinctive feature of the FCX Clarity—other than the fuel cell itself—is the streamlined layout made possible by its compact and efficient powertrain components.
The fuel cell combines hydrogen with oxygen to make electricity. The electricity then powers the electric motor, which in turn propels the vehicle. Water is the only byproduct the FCX Clarity leaves behind.

Roll over the numbered steps to learn about each stage of the process.
1. Hydrogen tank – Stores hydrogen
2. V Flow fuel cell stack – Generates electricity
3. Lithium-ion battery – Stores electricity
4. Power Drive Unit (PDU) – Governs electrical flow
5. Electric drive motor – Propels vehicle

From the start, Honda engineers designed this car to be tons of fun to drive. Acceleration in the FCX Clarity is smooth and powerful for a great overall driving experience.
Information gleaned from multiple generations of Honda fuel cell vehicles pays off right now. Compared to the previous model, the powertrain on this next-generation FCX Clarity:

•Is over 397 pounds lighter

•Has 120% better power-to-weight ratio

•Is 20% more fuel efficient

•Has a powertrain that is 45% more compact and 10% more energy-efficient

•Free and Clear

•First, the basics: a fuel cell vehicle is powered by an electric motor running on electricity generated by a hydrogen-powered fuel cell stack. The more efficient Honda E-Drive electric motor lets you drive with peace of mind knowing that you are helping to reduce the amount of CO2 being released in our atmosphere. The compact coaxial motor is quieter and can run at higher rpm, for greater efficiency and speed.

•Get Vertical

•The Vertical Flow (V Flow) fuel cell stack is one of Honda’s greatest breakthroughs in this area. The new design is smaller, allowing for better packaging efficiency. With a smaller stack, there’s room for more people. This ingenious design allows higher cell voltage stability and reduces the amount of heat generated. Gravity also helps with drainage of the excess water.
•Added Power

•The compact, high-efficiency lithium-ion battery pack is used as a supplemental power source capturing lost energy during deceleration and braking. The new lithium-ion battery delivers improved performance and energy recovery in a more lightweight, compact package. The new battery is significantly lighter and smaller than the ultra-capacitor of the 2005 FCX, allowing it to be stowed under the rear seat. This gives the car more passenger space and a bigger trunk.

•Low Profile

•Stylish? Definitely. It’s time to take another look at the FCX. This new model has a lower floor and sleeker overall design thanks to integration of the more compact stack and smaller powertrain. Thin A-pillars allow better visibility. A flat-bottom underbody reduces aerodynamic drag and increases efficiency.

•high safety standards can apply to all vehicles—even the groundbreaking ones. Six airbags are standard. Vehicle Stability Assist™ (VSA®) and Electronic Brake Distribution (EBD) systems are standard. Even a Collision Mitigation Braking System™ (CMBS™) is present and accounted for. And the FCX Clarity passed all the rigorous tests required by U.S. safety standards that other Honda models have endured. So you can drive the FCX Clarity with confidence.

SOLEX CARBURETTOR

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.

Peugeot leonin

Eco Factor: Concept car powered by electricity.

Concept car designer Liviu Tudoran has designed an eco-friendly electric car for Peugeot that complements the Lion image that we see in the car brand’s logo. The car, dubbed the Peugeot Leonin, is based on an electric engine mounted in the back of the car which is powered by a battery supply unit that rests under the front hood.Tudoran says that if developed, his car could reach a speed of about 160 km/h and will have a range of around 500km, which seems fantastic for a car that has been designed especially for short distance travel in a crowded city. The car’s body will be made from aluminum composite, hard plastic, carbon fiber and glass. Instead of an interior rearview mirror, the car will be equipped with an LCD screen in the main console that shows the video captured by the hi-resolution camera mounted on the back of the car.Basically, the idea of the designer is that the car should be a hybrid with a battery under the hood and the motor at the read of the car. Because more and more people are buying vehicles, this car would be perfect for a crowded city. The Peugeot Leonin concept could reach speeds of around 160 km/h hour or 100 mph. The main materials which could be used for this project are carbon fiber and glass, but this is still just a concept. Like many other futuristic cars, the look is still pretty unfamiliar, but I am sure that this car would be able to achieve a great success in a few years. more pictures after the jump

Audi Shark Concept by Kazim Doku

Audi-shark-concept

Audi (FRA:NSU) have certainly turned things up a gear when it comes to designing new vehicles, but who would have thought that they could top the Audi R8 FSI. Well looking at the pictures of the Audi Shark Concept, it proves that Audi still have a lot to give, I wish the future would come tomorrow so I could ride one of these things.
The Audi Shark is a futuristic flying concept vehicle with a streamlined design inspired by motorcycles and airplanes. It was designed by Kazim Doku and won the Desire Competition by Domus Academy.









The two-seater flying sportscar is inspired by the world of motorclycles and airplanes and offers its passengers "strong sensations and high levels of safety."
Both the headlights and the tail lights are made by transparent tubes which integrate LED units. The interior features sporty seats integrated in the cockpit structure.
The streamlined design of the exterior offers a visual reference to the car's name and - in combination with the rear lower spoiler - gives the vehicle an "underwater" appearance. Both the headlights and the tail lights are made by transparent tubes which integrate LED units. The interior features sporty seats integrated in the cockpit structure.

Citroen GT Concept

At The 2008 Paris Motor Show Citroën has unveiled the GT Concept, an extreme show car developed in partnership with Polyphony, maker of the Gran Turismo 5 PS3 videogame. The car features a racing-inspired design, dynamic sculpted lines and sharp graphics.

We see the same flamboyant air intake scoops on the sides as well as the inward pointing trapezoidal exhaust pipe. Also, a small glimpse of the taillight and rear hatch door with its chevron shaped air vent slats undoubtedly indicating a rear engine layout.

Citroen and Sony Playstation3 partner Polypony Digital are pouring the teaser marketing hype very thick. In this fifth (and most likely not the last) teaser installment, the Citroen GT concept is showing a little more of the back side this time with design characteristics.
Exterior Design

The design of GTbyCITROËN reflects a quest for optimal aerodynamic design. The show-car is a vehicle of flowing, taut lines, stretched to the extreme. The cleanly drawn sides, ribbed at the top, and the pearlescent shade of the bodywork enhance the vehicle's sleekly muscled looks.
The determined look of the front end is enhanced by wide air intakes and clear-cut horizontal headlamps. The headlamps feature penetrating blue LEDs in order to light the road effectively and keep rivals at a respectful distance! The chrome chevrons on the smooth bonnet express the Marque's identity.

The carbon rearview mirrors on their finely profiled supports appear to be suspended as if to cleave the air, giving an excellent on-road stance.

The large wraparound windscreen flows seamlessly into the roof and on into the rear mobile airfoil with its exaggeratedly long shape. The fast-flowing lines create the impression of a car in perpetual movement. The whole body expresses performance and continuous movement.

GTbyCITROËN also expresses strength and power through generous volumes, (length: 4.960m, 2.080m and height: 1.090m) underlined by strongly marked wheel arches. The diamond-effect 21-inch aluminium wheels enhance the car's sporty personality.

The up-country is upholstered in foul leather with deceptive touches of extraordinary materials such as copper and , the berth of Citroen GT concept is distinctly spiffy. The two padded racing seats are upholstered in suntanned leather, and each is bespoke with a four-point harness. The driver is assisted on a heads-up demonstrate which provides inexorable matter in an unobstructed to excitedly read make-up.

CARBURETTOR-9

BY-PASS CIRCUIT:

Slight throttle opening causes a drop in suction at the orifice controlled by volume control screw. While at the same time sufficient suction is not felt at the discharge of the Main spraying Nozzle. It however causes a depression at the By-Pass orifices situated in the body. This depression draws the air and fuel in the same manner as explained under idling, with the only difference that the emulsified fuel is now being discharged through the by-pass orifices also. This permits the engine to accelerate smoothly from idling to normal cruising speed.

THE MAIN JET SPRAYING SYSTEM

We have so far seen how the factors of easy starting in cold, s-low speed running and smooth transition are taken care of Apart from all these factors, emphasis is also given on maximum fuel economy as this is one of the burning problems of the day. Since in city traffic, the normal operating speed of the vehicle is around 40 to so KMPH, carburettors are designed to give optimum fuel economy at this speed. The mixture requirements to obtain fuel economy under normal cruising speed: (i.e. part throttle economy) is usually, leaner than what is required for maximum power. The main jet spraying system takes care of mixture ratios required for fuel economy and performance of engine during cruising speeds. As the throttle valve is progressively opened, air velocity in the choke tube begins to raise, thus creating depression across the spraying orifices. Now the petrol is drawn through the Main Jet and similarly air through the Air correction jet and emulsion tube with literal holes, (which helps emulsification of air and fuel) before the spray starts. Now mixture gets sprayed through the spraying nozzle holes and reaches the engine cylinder along with the air drawn through the main ventury of the carburettor.



THE ACCELERATING PUMP SYSTEM
(PBIC & PAIO carburettors)

This system is used on engines, requiring comparatively large choke-tubes or very weak cruising mixtures, td give optimum performance. A sudden wide opening of the throttle would quickly permit a large amount of air to pass through the choke- tube to the inlet valves without, possibly, creating sufficient depression at the Main spraying orifices to cause petrol to discharge from the Main Spraying well. A lack of petrol at this instant would mean that momentarily, a mixture too weak for proper combustion is fed to the engine, thus creating a condition of hesitancy on the part of the engine to accelerate. This condition is avoided by an injection of metered quantity of petrol at the right moment by the accelerating pump. The pump is actuated by a lever which is attached to the throttle spindle by means of a spring loaded rod. When the throttle is closed the tension of pump spring pushes the diaphragm assembly back, thus drawing petrol to the Pump chamber through the non return valve after getting filtered by a fine filter. Immediately on opening the throttle the lever pushes the diaphragm assembly forward forcing petrol out of the chamber, which is metered by the pump jet and finally into the choke tube via Injector tube. At the same time the ball valve is forced on to its seating, thus preventing the petrol, returning to the float chamber. The travel of lever, adjusted by means of the pump control rod nut, determines the volume of petrol injected and the size of the pump jet controls the rate of flow. Thus the Pump assists the engine to accelerate smoothly in operation. Please note that this comes into operation only on sudden pressing of accelerator and not for a particular position of the same.

PAIO ACCELERATING PUMP SYSTEM:

In 40 PAIO carburettors, an additional feature is given in the Accelerating Pump System, by way of an addition-al pump valve in the Accelerating Pump Assembly. This valve is mechanically operated and actuated by the diaphragm spindle itself and will come into operation only on full load conditions. when the throttle is in part load position, the pump valve is closed so that additional fuel cannot be discharged. when the throttle is in the full load position, the pump valve is opened and additional fuel is discharged to enrichen the mixture to take care of the load.

CARBURETTOR-8

Assemble and disassemble of Carburettors For 40 PAIO – Carburettors: Solex Down Draught Carburettors

The operation of this starter system is also by rotation of the Starter valve which is connected to the dash board control in the same way. (In this type we have two Discs, one for Air control and the other for petrol control) In-this system we have two positions of operation (viz.) Starter full open position and warm up position. Starter full open position

(a) During very cold weather (as these type of carburettors are fitted mainly to vehicles used by Army), when the choke knob is pulled fully away from dash board, it opens the disc valve. Now when the engine is cranked, due to suction created at starter discharge hole, the system draws air through float chamber cover, starter air bend and the small orifice (only little air for atomisation, as extreme cold conditions call for a complete rich mixture) and petrol via starter petrol jet, and passed through the petrol control valve. Now petrol is emulsified and the mixture passes through the starter discharge holes into the engine.

Starter Warm up position

In extreme cold conditions once the engine is started, a progressive fast idle is provided in this system for flexible control of cold engines.

In operation the starter provides a progressively weaker mixture as the dash board control is moved from the intermediate to full in position. This movement adjusts the mixture strength and gives the fast idling speed required to suit a warming engine and also provides a slightly rich mixture for quick drive away whilst the engine is still cold.

In the ‘Intermediate’ position which is located by a spring loaded ball under the starter lever, the dished hole in the petrol regulating valve is getting communicated to circuit from starter petrol jet. The orifice at the dished portion (smaller in size) reduces fuel input from starter petrol jet and combined with air drawn into channel shown as Air above throttle spindle, supplies a weaker mixture.

Rotation of valve as the dash board control is pushed home progressively reduces the starter discharge, thus causing the engine to slow down and the strength of the mixture is adjusted to suit the new conditions as the engine warms up. When the knob is fully closed the device is put out of action by the disc valve which closes the concerned petrol and Air orifices.

Driving away:

On opening the throttle with a cold engine, extra enrichment is provided by suction then being brought directly into the channel marked ‘Air’ above throttle, drawing mixture from the petrol channel. The degree of enrichment progressively diminishing as the disc valve is progressively closed.

THE SLOW SPEED JET SYSTEM

During slow speed, the engine normally requires a relatively richer mixture compared to what it would require under cruising conditions. The slow speed system consisting of the idling and the By-pass (transition) circuits, takes care of these requirements. The idling circuit comes into operation when the throttle valve is practically closed, and the By-pass circuit when the throttle is slightly opened. Usually there is a slight difference from engine to engine in the requirements of idling mixture and this changes with age and engine parameters like ignition timing, compression pressure etc. To take care of these variables Volume Control screw is provided to alter slightly the air-fuel mixture. Opening of the throttle required for idling speed is controlled by the slow running adjustment screw.

IDLING CIRCUIT:

When the engine is idling, suction felt underneath the throttle causes petrol to flow from the emulsion well to the Pilot Jet. The petrol, after being metered by the Pilot Jet combines with air metered by Pilot air bleed. The mixture then moving down to the volume control screw and through the discharge orifice in to the engine. With a given size of Pilot Jet and air bleed the volume of the idling mixture is controlled by screwing the volume control strew in or out, which respectively permits a reduced or increased quantity of air fuel mixture passing through the idling discharge orifice. For correct setting of the idling it is necessary to use both means of adjustment, i.e., volume control screw for mixture strength and slow running adjustment screw for speed.

CARBURETTOR-7

Air Control Solenoid Systems

Some computer-controlled carburetors have an O2 feed-back solenoid that allows air into the idle system or main system to control the air/fuel ratio. The computer uses a duty-cycle principle to control this solenoid. When the O2 sensor signal indicates a rich air/fuel ratio, the computer energizes the solenoid longer, which allows more air into the idle or main system to make the air/fuel ratio leaner. Conversely, if the O2 sensor signal is low indicating a lean air/fuel ratio, the computer reduces the solenoid on time and shuts off some of the airflow into the idle or main system to provide a richer air/fuel ratio. Other computer-controlled carburetors have a stepper motor that controls the airflow past a tapered valve on the motor stem into the main system. This stepper motor is popular on some variable venturi carburetors. A lean O2 sensor signal causes the computer to move the stepper motor stem and valve inward to close off some airflow to provide a richer air/fuel ratio. If the O2 sensor indicates a rich air/fuel ratio, the computer moves the stepper motor stem outward and allows more air flow into the main system to make the air/fuel ratio leaner. Since a certain amount of fuel is moving through the main system with the engine idling, the stepper motor controls airflow only into the main system.

ELECTRONIC IDLE-SPEED CONTROL

In order to maintain federally mandated emission levels, it is necessary to control the idle speed. Most feedback systems operate in open loop when the engine is idling. To reduce emissions during idle, most feedback carburetors idle faster and leaner than non feedback carburetors. To adjust idle speed, many feedback carburetors have an idle speed control (ISC) motor that is controlled by an electronic control module. The ISC motor is a small, reversible, electric motor. It is part of an assembly that includes the motor gear drive, and plunger. The direction of motor rotation dictates whether the plunger moves in or out. The ISC motor is mounted so that the plunger can contact the throttle level. The PCM controls the ISC motor and can change the polarity applied to the motor's armature in order to control the direction in which it turns. When the idle tracking switch is open (throttle closed), the PCM commands the ISC motor to control idle speed. The ISC provides the correct throttle opening for cold or warm engine idle.

Based on the input signals from the system's sensors, the PCM increases the curb idle speed if the coolant is below a specific temperature, if a load (such is air conditioning, transmission, or power steering) is placed on the engine, or when the vehicle is operated above a specific altitude. During closed choke idle, the fast-idle cam holds the throttle blade open enough to lift the throttle linkage off the ISC plunger. This allows the ISC switch to open so that the PCM does not monitor idle speed. As the choke spring allows the fast-idle cam to fall away and the throttle returns to the warm idle position, the PCM notes the still-low coolant temperature and commands a slightly higher idle speed. As the engine warms up, the plunger is retracted by the PCM. If the A/C compressor is turned on, the PCM extends the plunger a certain distance to increase engine idle speed to compensate for the added load. When the throttle is opened and the lever is no longer in contact with the plunger, an idle tracking switch (ITS) at the end of the plunger signals the PCM. The PCM then fully extends the plunger. During deceleration, the plunger makes contact with the lever and the unit acts like a dashpot. The throttle lever slowly closes. When the engine is shut down, the plunger retracts, preventing the engine from dieseling. It then extends for the next engine startup. In some systems, if the engine starts to overheat, the PCM commands a higher idle speed to increase coolant flow. Also, if system voltage falls below a predetermined value, the PCM commands a higher idle speed in order to increase AC generator speed and output.

Throttle Kicker and Idle Stop Solenoid

Some computer-controlled carburetors have a vacuum- operated throttle kicker and an idle stop solenoid. The throttle kicker maintains engine idle speed when the engine accessory load is increased, such as during A/C compressor clutch operation. This kicker also maintains idle speed during warm-up, after the fast idle cam has dropped away from the fast idle screw. Vacuum to the throttle kicker is controlled by an electric solenoid, which in turn is controlled by the power train control module (PCM). One end of the idle stop solenoid winding is connected to a terminal on the solenoid housing, and the other end of this winding is connected to ground on the solenoid housing. The idle stop solenoid terminal is connected to the ignition switch. When the ignition switch is turned on, current flows through the solenoid winding to ground. The magnetic field from this current flow pulls the solenoid plunger outward. Since the solenoid plunger contacts the throttle linkage, this plunger action moves the throttle linkage to provide the specified idle rpm. When the ignition switch is turned off, the idle stop solenoid plunger retracts and allows the throttle to move toward the closed position until the linkage contacts the throttle stop screw. This action prevents the engine from dieseling. On some computer-controlled carburetors, the throttle kicker and idle stop solenoid are combined in one unit, but the operation of both components is basically the same.

Vacuum-operated Throttle kicker

When a vacuum-operated throttle kicker (TK) and solenoid are used to control idle speed, the TK stem pushes against the throttle linkage. Under these operating conditions, the PCM energizes the solenoid and manifold vacuum is supplied to the TK diaphragm:

(1) During engine warm-up,

(2) When the air conditioning (A/C) is turned on, and

(3) When the engine begins overheating.

During other engine operating conditions, the TK solenoid is de-energized and vacuum is shut off to the TK diaphragm. Under this condition, the TK diaphragm stem is retracted and the idle speed is controlled by the idle speed adjustment screw.

Temperature Compensated Pump

The temperature compensated pump (TCP) solenoid is operated by the PCM. When the engine coolant temperature is cold, the TCP solenoid is de-energized, and this solenoid shuts off vacuum to the TCP diaphragm. When this action is taken, the TCP diaphragm seats the ball check and full accelerator pump output is available for improved cold acceleration. Once the engine coolant temperature is warmed up, the PCM energizes the TCP solenoid, which supplies vacuum to the TCP diaphragm

Variable Voltage Choke Relay

The variable voltage choke (WC) relay is operated by the PCM and connected to the electric choke cover terminal. If the engine coolant temperature and intake air temperatures are cold, the PCM energizes the choke relay and supplies voltage to the choke heater in the choke cover
every 2.5 seconds. This action reduces current to the choke heater and slows the choke opening. As the engine coolant and intake air temperature increase, the PCM increases the choke relay duty on time, which increases current to the choke heater and speeds up the choke opening. When the intake air temperature reaches 80°F (26.6°C), the PCM energizes the choke relay at l0% on time, and current is supplied to the choke heater continually to ensure that the choke continues to open.

CARBURETTOR-6

Mixture Control Solenoids

The more advanced feedback systems used electrical solenoids to control the metering rods. These solenoids are generally referred to as duty-cycle solenoids or mixture control (M/C) solenoids. The solenoid is normally wired through the ignition switch and grounded through the PCM. The solenoid is energized when the PCM supplies a ground for it. The PCM cycles the solenoid ten times per second. Each cycle lasts 100 milliseconds. The amount of fuel metered into the main fuel well is determined by how many milliseconds the solenoid is on during each cycle. The solenoid can be on almost 100% of the cycle, or it can be off nearly 100% of the time. The MC solenoid can control a fuel metering rod, an air bleed, or both.

Duty Cycle

On some computer-controlled carburetor systems, the computer grounds the o, feedback solenoid winding at a constant rate, called duo cycle. Although the duty cycle remains constant, the computer has the capability to change the length of time that the solenoid winding remains grounded. This is referred to as dwell time or on-time. For example, if a manifold vacuum leak is making the air/fuel ratio lean, the computer receives a continuously low 02 sensor voltage. When this continually lean signal is received, the computer provides a rich command to the 02 feedback solenoid winding. This rich command reduces the 02 feedback dwell time and leaves the solenoid plunger up longer to try to provide a stoichiometric air/fuel ratio. under this condition, the computer may leave the solenoid winding off for 90% of the time and on for 10% of the time on each cycle. The computer operates the 02 feedback solenoid to maintain the air/fuel ratio at stoichiometric under most operating conditions. If the 02 sensor sends a continually rich signal to the computer, the computer provides a lean command to the 02 feedback solenoid. When this action occurs, the computer may keep the solenoid winding on for 90% of the time and off for 10% of the time on each cycle to bring the mixture to the stoichiometric ratio.

Idle System Air/Fuel Ratio Control

The computer and the 02 feedback solenoid also control he air/fuel ratio when the engine is idling. An air passage extends from the top of the solenoid plunger into the idle system. When the solenoid plunger is moved upward, the top of the plunger blocks the air passage into the idle system, which provides a richer idle air/fuel ratio. If the computer grounds the solenoid winding and moves the plunger downward, the air passage is opened past the top of the plunger into the idle system. Under this condition, he idle air/fuel ratio is leaner. If a defect occurs in the 02 feedback system so that the computer no longer operates the 02 feedback solenoid, the spring moves the plunger upward and the air/fuel mixture is continually rich. Under this condition, fuel economy and performance are reduced and emissionlevels increase, but the vehicle can be driven to a service center.

CARBURETTOR-5

Difficulty at high speeds

Weak air-fuel mixtures supplied by the single jet carburettor will not give enough power at high speeds. Therefore some special system is required to enrich the mixture at high speeds. One such system uses a metering rod with stepped diameter end in the main jet. At ordinary cruising speeds, the larger diameter part of the metering rod is in the jet which gives less fuel flow. At higher speeds, however, the metering rod is pulled up so that now smaller diameter part is in the jet. This increases the fuel flow to provide rich mixture.

Acceleration difficulty

When sudden acceleration is desired, the throttle is opened suddenly. This causes the maximum amount of air to come at once but the fuel supply lags thereby causing what is called engine stumble or hesitation which is due to weak mixture.

To avoid this hesitation a separate pump is used which provides fuel momentarily, till the increased fuel supply from the main nozzle starts. The pump is connected through linkage to the accelerator pedal. When the pump is connected through linkage to the accelerator pedal. When the accelerator pedal is pressed, the outlet valve is opened and the fuel is forced out of the acceleration jet. When the pedal is released, however, the piston moves up thereby sucking the fuel in from the float chamber. The pump is thus ready for next discharge.

Variable venturi carburetors

A fixed venturi does not change shape and size to accommodate changing engine performance demands. Therefore, the speed of the air flowing through the venturi varies according to engine rpm and load. Because the vacuum in the venturi is the result of moving air the amount of fuel drawn from the discharge nozzle varies as air velocity in the venturi fluctuates. In some engine operating modes, the air speed, vacuum level, and fuel discharge are matched to the needs of the engine. At other times, the fuel discharge might be too little or too much. To compensate for the inadequacies of a fixed venturi, idle systems, power systems, and choke systems are needed to supplement the main metering system. These assist systems are not necessary when a variable venturi is used. A variable venturi increases in size as engine demands increase. In this way, .airflow speed through the venturi and the resulting pressure differential remain fairly constant. An example of a variable venturi carburetor. A vacuum diaphragm that receives vacuum from ports in the throttle bores between the venturi valves and the throttle plates controls the venturi valves. As the throttle plates open, vacuum in the throttle bore increases and the venturi valves open farther. As the valves open, tapered metering rods attached to the valves retract from metering jets in the sides of the throttle bores. This increases the size of the jet openings, allowing additional fuel to be drawn into the air stream so that the air/fuel ratio remains constant. By metering both the fuel and airflow simultaneously, better fuel economy and lower emissions are possible.

FEEDBACK CARBURETOR SYSTEMS

The last type of carburetor system used was the electronic feedback design, which provided better combustion by improved control of the air/fuel mixture. The feedback carburetor was introduced following the development of the three-way catalytic converter. A three-way converter not only oxidizes HC and CO but also chemically reduces oxides of nitrogen (NOx) When three-way catalytic converters were installed, engineers discovered that air/fuel ratios must be maintained very close to the stoichiometric ratio of 14.7:l in order for the converters to be effective in lowering emission levels. If the air/fuel ratio is richer than stoichiometric, HC and CO levels are high, and the converter cannot lower these emission levels to the desired limit.
However, with a rich mixture, the combustion temperature is lowered. Therefore, the production of NOx is also lower and the converter is very effective in controlling NO emissions under this condition. When the air/fuel ratio is leaner than the stoichiometric ratio, the levels of CO and HC are low, and the converter is very effective in controlling these pollutants.
However a lean air/fuel ratio bums hotter in the combustion chambers, and NO. emissions become very high. Under this condition, the converter is ineffective in controlling NO. emissions. Therefore, the air/fuel ratio must be controlled at, or very close to, the stoichiometric ratio in order for the three-way converter to reduce all three emission levels to the desired limit.
It was discovered that conventional carburetors did not provide accurate air/fuel ratio control under all conditions; therefore, the three-way converter was not effective in reducing emission levels on engines with these carburetors. Computer-controlled carburetors were designed to maintain the air/fuel ratio at, or near, the stoichiometric ratio under most operating conditions, which allows the catalytic converter to provide effective control of exhaust emissions. Monitoring the air/fuel ratio is the job of the exhaust gas oxygen sensor. An oxygen sensor senses the amount of oxygen present in the exhaust stream. A lean mixture produces a high level of oxygen in the exhaust. A rich mixture produces little oxygen in the exhaust. The oxygen sensor placed in the exhaust before the catalytic converter produces a voltage signal that varies with the amount of oxygen the sensor detects in the exhaust. If the oxygen level is high, the voltage output is low. If the oxygen level is low, the voltage output is high. An electronic control unit (the PCM) monitors the electrical output of the oxygen sensor. This microprocessor is programmed to interpret the input signals from the sensor and in turn to generate output signals to a mixture control device that meters more or less fuel into the air charge as it is needed to maintain the 14.7 to 1 ratio. Whenever these components are working to control the air/fuel ratio, the carburetor is said to be operating in closed loop. Closed loop is illustrated in the schematic. The oxygen sensor is constantly monitoring the oxygen in the exhaust, and the PCM is constantly making adjustments to the air/fuel mixture based on the fluctuations in the sensor's voltage output. However there are certain conditions under which the PCM ignores the signals from the oxygen sensor and does not regulate the ratio of fuel to air. During these times, the carburetor is functioning in a conventional manner and is said to be operating in open loop. The carburetor operates in open loop until the oxygen sensor reaches a certain temperature (approximately 600°F [316°C]). The carburetor also goes into open loop when a richer than normal air/fuel mixture is required, such as during warm-up and heavy throttle application. Several other sensors are needed to alert the PCM to these conditions. Open loop also occurs when the engine’s coolant is cold. Under this condition, the 02 sensor is too cold to produce a satisfactory signal, and the computer program controls the air/fuel ratio without the 02 sensor input. During open loop mode, the computer provides a rich air/fuel ratio. Since a computer-controlled carburetor also has a conventional choke, a richer air/fuel ratio is supplied. As the engine approaches normal operating temperature, the computer goes into closed loop and begins to use the O2, sensor signal to control the air/fuel ratio. Closed loop in many computer-controlled carburetor systems occurs when the engine coolant temperature (ECT) sensor informs the computer that the coolant temperature has reached the specified level. Therefore, the ECT sensor signal is very important, because it determines the open or closed loop status. For example, if the engine thermostat is defective and the coolant temperature never reaches normal operating temperature, the PCM never enters closed loop. When this open loop condition occurs, the air/fuel ratio is continually rich and fuel economy is reduced. Some systems go back into open loop during prolonged periods of idle operation when the 02 sensor cools down. Many systems revert to open loop at, or near wide-open throttle to provide a richer air/fuel ratio.

CARBURETTOR-4

Carburetion

The three general stages involved in carburetion are metering, atomization, and vaporization. Metering is another term for measuring. In the process of carburetion, fuel is metered into the air passing through the barrel of the carburetor. The ideal air/fuel ratio at which all the fuel blends with all the oxygen in the air is called the stoichiometric ratio. This ratio is about 14.7:l . If there is more fuel in the mixture it is called a rich mix. If there is less fuel it is called a lean mix. The amount of fuel metered into the air is varied in relation to the amount of air passing through the carburetor. Atomization is the stage in which the metered fuel is drawn into the air stream in the form of tiny droplets. The droplets of fuel are drawn out of passages called discharge ports. The surface area of an atomized droplet is in contact with a relatively large amount of surrounding air. In addition, the venturi is a low-pressure area. The boiling point of the fuel is greatly reduced by lower pressures; therefore liquid gasoline can become a vapor with low amounts of heat. These factors combine to create a fine mist of fuel below the venturi in the bore. This is called vaporization-the last stage of carburetion. It occurs below the venturi, in the intake manifold, and within the cylinder. Swirl, turbulence, and heat within the intake manifold and cylinder also enhance vaporization.

BASIC CARBURETOR CIRCUITS

Variations in engine speed and load demand different-amounts of air and fuel (often in differing proportions) for best performance-and present complex problems for the carburetor. At engine idle speeds, for example, there is insufficient air velocity to cause fuel to be drawn from the discharge nozzle and into the air stream. Also, with a sudden change in engine speed, such as rapid acceleration, the venturi effect (pressure differential) is momentarily lost. Therefore, the carburetor must have special circuits or systems to cope with these situations. The basic circuits of a typical carburetor include the float, idle, main metering, power enrichment, accelerator pump, and choke:

The float circuit or fuel inlet system stores fuel and holds it at a precise level.

The idle circuit supplies the richer air/fuel mixture to operate the engine at idle and low speeds.

The main metering circuit provides the air/fuel mixture during open throttle conditions.

The power enrichment circuit supplies a richer mixture during heavy loads. In many carburetors, metering rods placed in the main jets provide power enrichment.

The accelerator pump circuit mechanically adds fuel to the mixture when the throttle is quickly opened.

The choke circuit provides a richer mixture during cranking and cold start-up by restricting the air flow into the carburetor.

CARBURETOR SYSTEMS

To meet complex fuel economy and emission requirements, carburetors were fitted with a variety of auxiliary controls. The following describes some of the more common assist devices you are likely to encounter when servicing a carburetor.

Choke Qualifier

Once the engine has started, a leaner mixture is needed. If the choke stays shut, the rich mixture floods the engine and causes stalling. Therefore, the automatic choke has a choke qualifying mechanism to open the choke plate slightly after the engine has started.

Dashpot

The dashpot is used during rapid deceleration to retard the closing of the throttle. This allows a smooth transition from the main metering system to the idle system and prevents stalling due to the overly rich air/fuel mixture. It also controls the level of HC in the exhaust during deceleration.

Hot-Idle Compensator (HIC) Valve

When the engine is overheated, a hot-idle compensator opens an air passage to lean the mixture slightly. This increases idle speed to help cool the engine (by increased coolant flow) and prevents excess fuel vaporization with-in the carburetor. The hot-idle compensator is a bimetal, thermostatically controlled air bleed valve. Vacuum Break Some carburetors are equipped with a fuel vacuum break system, which includes a primary diaphragm and a secondary diaphragm. The primary vacuum diaphragm opens the choke valve slightly as soon as the engine starts to keep the engine from over-choking and stalling. The secondary vacuum diaphragm, which is also attached to the choke lever opens the choke valve slightly wider in warm weather or when a warm engine is being started.

Choke Unloader

To be able to start a cold engine that has been flooded with gasoline, a choke unloader is required. The choke unloader is throttle-linkage-actuated and opens the choke whenever the accelerator pedal is floored. At wide-open throttle, the partially opened choke allows additional air to lean out the mixture and reduce fuel flow.

Throttle Position Solenoid

The throttle position solenoid is used to control the position of the throttle plate. It can have several functions, depending on its application. when the basic function is to prevent dieseling, the solenoid is called a throttle stop solenoid or an idle stop solenoid. when the engine is started, the solenoid is energized and touches the throttle plates that open slightly to the curb idle position. when the ignition switch is turned off, the solenoid allows the throttle plate to close completely, and shuts off the air/fuel supply to prevent dieseling or run-on. The throttle position solenoid is also used to increase the curb idle speed to compensate for extra loads on the engine. when this is its primary function, the solenoid might also be called an idle speed-up solenoid or a throttle kicker. This feature is most often used on cars with air conditioners.

TYPES OF CARBURETORS

Many types of carburetors have been built in order to accommodate different load conditions, engine designs, and air/fuel requirements. Carburetor Barrels A carburetor barrel is a passageway or bore used to mix the air and fuel. It consists of the throttle plate, venturi, and air horn. A one-barrel carburetor is used on small engines that do not require large quantities of air and fuel. A two-barrel carburetor has two throttle plates and two venturis. The area where the air comes into the carburetor is common on both barrels. A two-barrel carburetor may have one barrel that is smaller in diameter than the other one. shows a four-barrel carburetor. It has four barrels to mix the air and fuel. The engine operates on two barrels during most driving conditions. When more horsepower and torque is needed, the other two barrels add air and fuel to increase the output of the engine. When all throttle plates open and close simultaneously, the carburetor is called a single-stage carburetor. Some carburetors have two stages, called primary and secondary stages. In the primary stage, one or two throttle plates operate normally as in a single stage carburetor. The secondary stage throttle plates, however only open after the primary throttle plates have opened a certain amount. Thus, the primary stage controls off-idle and low cruising speeds, and the secondary stage opens when high cruising speeds or loads require additional air and fuel. The secondary throttle plates can be opened mechanically or by a vacuum source. Mechanically actuated secondary throttle plates are opened by a tab on the primary throttle linkage. After the throttle primary plates open a set amount, the tab engages the secondary throttle linkage, forcing the plates open. Vacuum-actuated secondaries have a spring-loaded diaphragm. Vacuum is supplied to the diaphragm from ports in the primary and secondary throttle bores. When the vacuum in the primary bore reaches a specific level, the vacuum supplied to the diaphragm overcomes the spring and opens the secondary throttle plates. The vacuum created in the secondary throttle bore increases the vacuum signal to the diaphragm, opening the secondary throttle valves still farther. nozzle I only. When the throttle valve is opened further, more suction moves cap E still further subjecting nozzle 2 also to engine suction along with nozzle 1. Now both nozzles I and 2 will deliver the fuel. But nozzle 2 is so adjusted that it gives lesser amount of fuel than nozzle l, thus providing compensation. Similarly, nozzles 3 and 4 which deliver still lesser amount of fuel are put into operation by further throttle opening.

(e) Suction controlled devices. These devices are operated by means of engine suction, which is applied to a sliding piston. The suction effect is increased as the engine speed is increased, which controls the movement of the piston which further controls the venturi area. Sometimes the engine suction is also used to actuate a needle which decreases the effective nozzle area as the speed is increased, thus providing compensation. This method is used in the S.U. Carburettor, which has been discussed in detail in Art 23 .