Vehicles by Country Wise

Argentina	Anasagasti Crespi Hispano-Argentina IAME IKA
Australia	Elfin Sports Cars FPV Holden HSV Tickford
Belgium	Auto-Mixte Gillet Nagant Pieper
Brazil	Agrale Lobini TAC Motors Troller
Defunct	Puma Gurgel
Canada	Bricklin Studebaker Derby
Czech Republic	Avia Kaipan Praga Skoda Auto Tatra
France	Aixam Alpine Citroen Delahaye Facel Hommell Ligier Microcar MDI Pescarolo Sport Peugeot Renault Bugatti
Germany	Audi AWZ Barkas Bitter BMW Borgward Bugatti Büssing DKW Glas Goliath Hansa Heinkel Horch Lloyd Maybach MAN Mansory Mercedes-Benz Multicar NAG Neoplan Opel Porsche Robur Simson Trabant Volkswagen Wanderer RUF Wiesmann
India	Bajaj Hero MotoCorp Maruti Motors Mahindra & Mahindra Limited TAFE Tata Motors TVS Premier Automobiles Limited Ashok Leyland Chinkara Motors DC Design Force Motors Hindustan Motors Eicher ICML GKD
Iran	Bahman Group IKCO (Iran Khodro) Kerman Motors Kish Khodro MVM Pars Khodro SAIPA HARISARU
Italy	Alfa Romeo DR Motor Ferrari Fiat Intermeccanica Lamborghini Lancia Maserati Pagani Siata Vignale De Tomaso Autobianchi Cizeta
Japan	Acura Daihatsu Datsun Hino Honda Infiniti Isuzu Lexus Mazda Mitsubishi Motors Mitsuoka Nissan Scion Subaru Suzuki Toyota Yamaha Dome Motors
Malaysia	Bufori Inokom Naza Perodua Proton TD2000
Mexico	Mastretta DINA Tranvias-Cimex Italika
Manaco	Venturi
Netherlands	DAF Huet Brothers Donkervoort Spyker
Pakistan	Daewoo Hinopak Motors Dewan Farooque Motors Ghandhara Industries
Poland	Syrena Fabryka Samochodów Osobowych Warszawa (car) ZSD Nysa FSC Żuk
Romania	Automobile Dacia ARO Oltcit Tractorul Braşov
Russia	Avtoframos GAZ (Volga) Lada Marussia Motors Moskvitch Russo-Balt UAZ Yo-Mobile Zil
Serbia	FAP - Fabrika Automobila Priboj Ikarbus Neobus Fiat Automobili Srbija Zastava special cars Industry of Machinery and Tractors
Sri Lanka	Micro (cars)
South Africa	BMW South Africa Ford Motor Company of Southern Africa General Motors Southern Africa Mercedes-Benz South Africa Nissan South Africa Renault South Africa Toyota South Africa Volkswagen Group South Africa
South Korea	GM Daewoo(Chevrolet Korea) Hyundai Motor Company Kia Motors Renault Samsung Motors SsangYong Motor Company Proto Motors
Spain	Irizar SEAT Tauro Sport Auto Tramontana
Sweden	Koenigsegg Jösse Car Saab Scania Volvo
Switzerland	Enzmann Stealth Sbarro (automobile)
Thailand	Thai Rung Union Car
Turkey	Tofaş-Fiat Anadol Otosan Karsan Oyak-Renault Otokar Temsa BMC (Turkey) Toyota Hyundai Assan Isuzu Anadolu Turk Traktor Hattat Mercedes-Benz Turkey Honda Turkey
United Kingdoms	AC                         Allard Alvis Armstrong Siddeley Ascari Aston Martin Austin Austin-Healey Bentley Bristol British Leyland Caterham Daimler Elva Ford Ginetta Gordon Keeble Hillman Humber Jaguar Cars Jensen Jowett Lanchester Land Rover Gengatharan automobiles limited Lister Lotus Marcos McLaren Automotive MG MG Cars Mini Mini Cooper Morgan Morris Noble Riley Rolls Royce Rover Singer Standard Sunbeam Triumph Trojan TVR Vauxhall Wolseley
United States	Buick Cadillac Chevrolet Coda Chrysler Dodge Dodge Ram Fisker Ford Fiat Global Electric Motorcars GMC Hyundai International Harvester Jeep Kia Lincoln Navistar International Tesla Callaway Saleen Panoz Mosler E-Z-GO Nissan Toyota Volvo
Defunt US	American Motors Apollo Auburn Bates Motor company Cord Davis Motor Car DeLorean Motor Company Duesenberg Eagle Edsel Essex Geo Graham-Paige Hummer Hupmobile Kaiser Motors Kissel Motor Car Company Laforza Lasalle Locomobile Marmon Mercury Nash Motors Oldsmobile Packard Pierce-Arrow Plymouth Pontiac Regal REO Saturn Sterling Studebaker Tucker Thomas B. Jeffery Company Willys Sound
Uzbekistan	GM Uzbekistan JV MAN Auto – Uzbekistan SamAvto

How Air Bags Works

                               Imagine you're in your car driving home. The weather isn't particularly bad, the road conditions are fine, and you're singing along with the radio. Then out of nowhere, a car makes an illegal turn, winds up in front of you, and you don't have time to stop. You hear the screech of metal as your car collides with the other, and brace yourself to go flying through the windshield. Instead, you are pushed backward into your seat, held there for a split second, and then the pressure subsides. Your seatbelt was the first line of defense but you are upright in the driver's seat because your car is equipped with a vehicle airbag.



Manufacturers have many different names for their systems:
            *Supplementary Restraint System (SRS)             *Air Cushion Restraint System (ACRS)
            *Supplemental Inflatable Restraint (SIR)

But, they all have the same purpose and operation.

              Airbags are supplemental restraints. Supplemental means they help another system, or they are secondary to another system. In this case it is the seat belt. Though later airbags are required to be able to, airbags are not meant to be used without a seat belt; in fact they can be very dangerous or even deadly without a seat belt.Contrary to what a lot of people think air bags are not made to stop you from lunging forward during a crash.  In a crash, let’s say 30 mph, the car is moving 30 mph and your body is moving 30 mph along with it, if the car hits a wall and stops, not being part of the car your body is still moving at 30 mph, causing you to lunge forward.
This is the job of the seat belt, to hold you in place.

Have you ever wondered how race car drivers have such horrible crashes and never get hurt?
               Let’s look at a race car, with a five point harness the driver is a stationary part of the seat. He can not move forward or backward, there is no slack in the harness, he is actually a part of the car. Then look at the 200 mph crashes they walk away from without a scratch. Why? Because his body stopped at the same time as the car did. Now look at a passenger vehicle: Who wants to be restrained that tight in a car on the city streets, or on a long trip? Our seat belts have some slack in them; therefore not being a stationary part of the vehicle, we are going to lunge forward some what in a crash.

This is where the air bag, or supplement, comes in.
The air bag deploys at 200-300 mph, depending on the manufacture. From the time of impact to the time of full airbag deployment is from 21 to 27 milli-seconds. This means it is already fully deployed before yourbody ever lunges forward.

The idea is for the air bag to be deployed, so fast that it is fully inflated, before your body is thrown forward. Then as you fall into the bag, it should have already started to deflate. The bag then lowers you down at a slower speed and cushions you.

                         The design is conceptually simple; a central "Airbag control unit"(ACU) (a specific type of ECU) monitors a number of related sensors within the vehicle, including accelerometers, impact sensors, side (door) pressure sensors,wheel speed sensors, gyroscopes, brake pressure sensors, and seat occupancy sensors. The bag itself and its inflation mechanism is concealed within the steering wheel boss (for the driver), or the dashboard (for the front passenger), behind plastic flaps or doors which are designed to "tear open" under the force of the bag inflating. Once the requisite 'threshold' has been reached or exceeded, the airbag control unit will trigger the ignition of a gas generator propellant to rapidly inflate a fabric bag. As the vehicle occupant collides with and squeezes the bag, the gas escapes in a controlled manner through small vent holes. The airbag's volume and the size of the vents in the bag are tailored to each vehicle type, to spread out the deceleration of (and thus force experienced by) the occupant over time and over the occupant's body, compared to a seat belt alone.

The signals from the various sensors are fed into the Airbag control unit, which determines from them the angle of impact, the severity, or force of the crash, along with other variables. Depending on the result of these calculations, the ACU may also deploy various additional restraint devices, such as seat belt pre-tensioners, and/or airbags (including frontal bags for driver and front passenger, along with seat-mounted side bags, and "curtain" airbags which cover the side glass). Each restraint device is typically activated with one or more pyrotechnic devices, commonly called an initiator or electric match. The electric match, which consists of an electrical conductor wrapped in a combustible material, activates with a current pulse between 1 to 3 amperes in less than 2 milliseconds. When the conductor becomes hot enough, it ignites the combustible material, which initiates the gas generator. In a seat belt pre-tensioner, this hot gas is used to drive a piston that pulls the slack out of the seat belt. In an airbag, the initiator is used to ignite solid propellant inside the airbag inflator. The burning propellant generates inert gas which rapidly inflates the airbag in approximately 20 to 30 milliseconds. An airbag must inflate quickly in order to be fully inflated by the time the forward-traveling occupant reaches its outer surface. Typically, the decision to deploy an airbag in a frontal crash is made within 15 to 30 milliseconds after the onset of the crash, and both the driver and passenger airbags are fully inflated within approximately 60-80 milliseconds after the first moment of vehicle contact. If an airbag deploys too late or too slowly, the risk of occupant injury from contact with the inflating airbag may increase. Since more distance typically exists between the passenger and the instrument panel, the passenger airbag is larger and requires more gas to fill it.

Front airbags normally do not protect the occupants during side, rear, or rollover accidents.Since airbags deploy only once and deflate quickly after the initial impact, they will not be beneficial during a subsequent collision. Safety belts help reduce the risk of injury in many types of crashes. They help to properly position occupants to maximize the airbag's benefits and they help restrain occupants during the initial and any following collisions.

In vehicles equipped with a rollover sensing system, accelerometers and gyroscopes are used to sense the onset of a rollover event. If a rollover event is determined to be imminent, side-curtain airbags are deployed to help protect the occupant from contact with the side of the vehicle interior, and also to help prevent occupant ejection as the vehicle rolls over.

Chemistry Behind Air Bags:
                       Inside the airbag is a gas generator containing a mixture of NaN3, KNO3, and SiO2. When the car undergoes a head-on collision, a series of three chemical reactions inside the gas generator produce gas (N2) to fill the airbag and convert NaN3, which is highly toxic (The maximum concentration of NaN3 allowed in the workplace is 0.2 mg/m3 air.), to harmless glass (Table 1). Sodium azide (NaN3) can decompose at 300oC to produce sodium metal (Na) and nitrogen gas (N2). The signal from the deceleration sensor ignites the gas-generator mixture by an electrical impulse, creating the high-temperature condition necessary for NaN3 to decompose. The nitrogen gas that is generated then fills the airbag. The purpose of the KNO3 and SiO2 is to remove the sodium metal (which is highly reactive and potentially explosive, as you recall from the Periodic Properties Experiment) by converting it to a harmless material. First, the sodium reacts with potassium nitrate (KNO3) to produce potassium oxide (K2O), sodium oxide (Na2O), and additional N2 gas. The N2 generated in this second reaction also fills the airbag, and the metal oxides react with silicon dioxide (SiO2) in a final reaction to produce silicate glass, which is harmless and stable. (First-period metal oxides, such as Na2O and K2O, are highly reactive, so it would be unsafe to allow them to be the end product of the airbag detonation).

Published by Ravindra(Mechanical Engineering)

                                         

Anti Break Locking System

               When the driver brakes hard on a slippery road surface, the anti-lock braking system prevents the wheels from locking, so that the vehicle can still be steered.

               When the wheels lock up, they are no longer able to transmit cornering forces, meaning that the driver loses control of the vehicle. To prevent this from happening, the ABS control unit uses wheel speed sensors to monitor the rotational speed of each wheel. If it detects that a wheel is about to lock, a solenoid valve in the anti-lock braking system's central control element reduces the brake pressure applied at the wheel in question until it starts to rotate freely again. The pressure is subsequently increased to the lock-up threshold again. The vehicle remains stable and can still be steered.
                 Since most cars on the road today have some form of Antilock Brakes (ABS) I think we should take a look at how they work and clear up some mis-information about them.

                As always, what I describe here is how most systems work in general. Since different manufacturers have their own versions of ABS their specifications and part names may differ. If you're having a problem with the ABS on your vehicle you should always refer to the specific service and repair manuals for your vehicle.

               The ABS is a four-wheel system that prevents wheel lock-up by automatically modulating the brake pressure during an emergency stop. By preventing the wheels from locking, it enables the driver to maintain steering control and to stop in the shortest possible distance under most conditions. During normal braking, the ABS and non-ABS brake pedal feel will be the same. During ABS operation, a pulsation can be felt in the brake pedal, accompanied by a fall and then rise in brake pedal height and a clicking sound.

Vehicles with ABS are equipped with a pedal-actuated, dual-brake system. The basic hydraulic braking system consists of the following:
*ABS hydraulic control valves and electronic control unit
*Brake master cylinder
*Necessary brake tubes and hoses

The anti-lock brake system consists of the following components:
*Hydraulic Control Unit (HCU).
*Anti-lock brake control module.
*Front anti-lock brake sensors / rear anti-lock brake sensors.

Anti-lock Brake Systems (ABS) operate as follows:

1.When the brakes are applied, fluid is forced from the brake master cylinder outlet ports to the HCU inlet       ports. This pressure is transmitted through four normally open solenoid valves contained inside the HCU,       then through the outlet ports of the HCU to each wheel.
2.The primary (rear) circuit of the brake master cylinder feeds the front brakes.
3.The secondary (front) circuit of the brake master cylinder feeds the rear brakes.
4.If the anti-lock brake control module senses a wheel is about to lock, based on anti-lock brake sensor          data, it closes the normally open solenoid valve for that circuit. This prevents any more fluid from entering      that circuit.
5.The anti-lock brake control module then looks at the anti-lock brake sensor signal from the affected wheel    again.
6.If that wheel is still decelerating, it opens the solenoid valve for that circuit.
7.Once the affected wheel comes back up to speed, the anti-lock brake control module returns the solenoid    valves to their normal condition allowing fluid flow to the affected brake.
8.The anti-lock brake control module monitors the electromechanical components of the system.
9.Malfunction of the anti-lock brake system will cause the anti-lock brake control module to shut off or            inhibit the system. However, normal power-assisted braking remains.
10.Loss of hydraulic fluid in the brake master cylinder will disable the anti-lock system. [li[The 4-wheel anti-      lock brake system is self-monitoring. When the ignition switch is turned to the RUN position, the anti-            lock brake control module will perform a preliminary self-check on the anti-lock electrical system                  indicated by a three second illumination of the yellow ABS wanting indicator.
11.During vehicle operation, including normal and anti-lock braking, the anti-lock brake control module              monitors all electrical anti-lock functions and some hydraulic operations.
12.Each time the vehicle is driven, as soon as vehicle speed reaches approximately 20 km/h (12 mph), the
     anti-lock brake control module turns on the pump motor for approximately one-half second. At this time,      a mechanical noise may be heard. This is a normal function of the self-check by the anti-lock brake                control module.
13.When the vehicle speed goes below 20 km/h (12 mph), the ABS turns off.
14.Most malfunctions of the anti-lock brake system and traction control system, if equipped, will cause the
     yellow ABS warning indicator to be illuminated.

             Most light trucks and SUVs use a form of ABS known as Rear Wheel ABS. The Rear Wheel Anti Lock (RWAL) system reduces the occurrence of rear wheel lockup during severe braking by regulating rear hydraulic line pressure. The system monitors the speed of the rear wheels during braking. The Electronic Brake Control Module (EBCM) processes these values to produce command controls to prevent the rear wheels from locking.

This system uses three basic components to control hydraulic pressure to the rear brakes. These components are:
*Electronic Brake Control Module
*Anti-Lock Pressure Valve
*Vehicle Speed Sensor

ELECTRONIC BRAKE CONTROL MODULE:
             The EBCM mounted on a bracket next to the master cylinder, contains a microprocessor and software for system operation.

ANTI-LOCK PRESSURE VALVE:
            The Anti-Lock Pressure Valve (APV) is mounted to the combination valve under the master cylinder, has an isolation valve to maintain or increase hydraulic pressure and a dump valve to reduce hydraulic pressure.

VEHICLE SPEED SENSOR:
            The Vehicle Speed Sensor (VSS) located on the left rear of the transmission on two-wheel drive trucks and on the transfer case of four-wheel drive vehicles, produces an AC voltage signal that varies in frequency according to the output shaft speed. On some vehicles the VSS is located in the rear differential.

BASE BRAKING MODE:
           During normal braking, the EBCM receives a signal from the stop lamp switch and begins to monitor the vehicle speed line. The isolation valve is open and the dump valve is seated. This allows fluid under pressure to pass through the APV and travel to the rear brake channel. The reset switch does not move because hydraulic pressure is equal on both sides.

ANTILOCK BRAKING MODE:
           During a brake application the EBCM compares vehicle speed to the program built into it. When it senses a rear wheel lock-up condition, it operates the anti lock pressure valve to keep the rear wheels from locking up. To do this the EBCM uses a three-step cycle:
*Pressure Maintain
*Pressure Decrease
*Pressure Increase

PRESSURE MAINTAIN:
During pressure maintain the EBCM energizes the isolation solenoid to stop the flow of fluid from the master cylinder to the rear brakes. The reset switch moves when the difference between the master cylinder line pressure and the rear brake channel pressure becomes great enough. If this happens, it grounds the EBCM logic circuit.

PRESSURE DECREASE:
             During pressure decrease the EBCM keeps the isolation solenoid energized and energizes the dump solenoid. The dump valve moves off its seat and fluid under pressure moves into the accumulator. This action reduces rear pipe pressure preventing rear lock-up. The reset switch grounds to tell the EBCM that pressure decrease has taken place.

PRESSURE INCREASE:
               During pressure increase the EBCM de-energizes the dump and isolation solenoids. The dump valve reseats and holds the stored fluid in the accumulator. The isolation valve 9pens and allows the fluid from the master cylinder to flow past it and increase pressure to the rear brakes. The reset switch moves back to its original position by spring force. This action signals the EBCM that pressure decrease has ended and driver applied pressure resumes.

SYSTEM SELF-TEST:
                 When the ignition switch is turned "ON," the EBCM performs a system self-test. It checks its internal and external circuit and performs a function test by cycling the isolation and dump valves. The EBCM then begins its normal operation if no malfunctions are detected.

                 Brake pedal pulsation and occasional rear tire "chirping" are normal during RWAL operation. The road surface and severity of the braking maneuver determine how much these will occur. Since these systems only control the rear wheels, it is still possible to lock the front wheels during certain severe braking conditions.

SPARE TIRE:
             Using the spare tire supplied with the vehicle will not affect the performance of the RWAL or system.

REPLACEMENT TIRES:
                  Tire size can affect the performance of the RWAL system. Replacement tires must be the same size, load range, and construction on all four wheels.

             Contrary to popular belief ABS brakes will not stop your car faster. The idea behind ABS brakes is that you maintain control of your vehicle by avoiding wheel lock up. When your wheels lock up you have no steering control and turning the steering wheel to avoid a collision will do you no good. When the wheels stop turning, it's done and over.
When driving on slippery roads you need to allow for increased braking distance since the wheels will lock up much easier and the ABS will cycle much faster. Speed is a factor also, if you're going too fast even the control ABS gives you will not be enough to overcome plain inertia. You may turn the wheel to the left or right, but inertia will keep you going forward.
If there is an ABS failure, the system will revert to normal brake operation so you will not be without brakes. Normally the ABS warning light will turn on and let you know there is a fault. When that light is on it is safe to assume the ABS has switched to normal brake operation and you should drive accordingly.

                I hope that this has helped you understand how ABS systems work. It is a technology that has been in use for many years before it was adapted for automotive use. Aircraft have been using some form of ABS since WW II and it is a tried and true system that can be a great help in avoiding accidents if it is used as it was meant to be used.

Advantages of Anti-Lock Brakes:
The main benefits of an anti-lock brake system (ABS) include:

*Stopping on ice:
             As mentioned above, an ABS prevents lock-ups and skidding, even in slippery conditions.   Anti-lock brakes have been proven to save lives in some situations by helping drivers keep control of a         vehicle.
*Lower insurance costs:
             Because it is a thoroughly tested safety device with a track record of effectiveness,insurers often give customers specific discounts for having an ABS system on their vehicle.
*Higher resale value:
               As a feature on a car or truck, an ABS raises the market value of the vehicle.Nowadays, where ABS technology has become standard on many vehicles, not having it could result in a     lower price for resale.
*Traction control:
                  An ABS shares some of the infrastructure of a traction control system, where new  technology helps ensure that each wheel has traction on the road. That makes it easy for manufacturers to install both of these features at the factory.

Disadvantages of Anti-Lock Brakes:

        Despite the fact that anti-lock brakes are proven to be a safety feature in most situations, and insurers consider them to significantly lower risk for a vehicle, not all drivers are sold on this option for a car or truck. Here are some of the down sides that drivers find in this kind of brake system.
Inconsistent stop times:
              Anti-lock brakes are made to provide for surer braking in slippery conditions. However, some drivers report that they find stopping distances for regular conditions are lengthened by their ABS, either because there may be errors in the system, or because the clunking or noise of the ABS may contribute to the driver not braking at the same rate.
Expense:
             An ABS can be expensive to maintain. Expensive sensors on each wheel can cost hundreds of dollars to fix if they get out of calibration or develop other problems. For some, this is a big reason to decline an ABS in a vehicle.
Delicate systems:
             It's easy to cause a problem in an ABS by messing around with the brakes. Problems include disorientation of the ABS, where a compensating brake sensor causes the vehicle to shudder, make loud noise or generally brake worse.

                  Published by Ravindra.K(Mechanical Engineering)

Carburetor

Introduction:
          carburetor, also spelled carburettor , device for supplying a spark-ignition engine with a mixture of fuel and air. Components of carburetors usually include a storage chamber for liquid fuel, a choke, an idling (or slow-running) jet, a main jet, a venturi-shaped air-flow restriction, and an accelerator pump. The quantity of fuel in the storage chamber is controlled by a valve actuated by a float. The choke, a butterfly valve, reduces the intake of air and allows a fuel-rich charge to be drawn into the cylinders when a cold engine is started. As the engine warms up, the choke is gradually opened either by hand or automatically by heat- and engine-speed-responsive controllers. The fuel flows out of the idling jet into the intake air as a result of reduced pressure near the partially closed throttle valve. The main fuel jet comes into action when the throttle valve is further open. Then the venturi-shaped air-flow restriction creates a reduced pressure for drawing fuel from the main jet into the air stream at a rate related to the air flow so that a nearly constant fuel-air ratio is obtained. The accelerator pump injects fuel into the inlet air when the throttle is opened suddenly.

In the 1970s, new legislation and consumer preferences led automobile manufacturers to improve fuel efficiency and lower pollutant emissions. To accomplish these objectives, engineers developed fuel injection management systems based on new computer technologies. Soon, fuel injection systems replaced carbureted fuel systems in virtually all gasoline engines except for two-cycle and small four-cycle gasoline engines, such as those used in lawn mowers.
If you have read the page entitled How Car Engines Work, you know that the idea behind an engine is to burn gasoline to create pressure, and then to turn the pressure into motion. A remarkably tiny amount of gasoline is needed during each combustion cycle. Something on the order of 10 milligrams of gasoline per combustion stroke is all it takes!

The goal of a carburetor is to mix just the right amount of gasoline with air so that the engine runs properly. If there is not enough fuel mixed with the air, the engine "runs lean" and either will not run or potentially damages the engine. If there is too much fuel mixed with the air, the engine "runs rich" and either will not run (it floods), runs very smoky, runs poorly (bogs down, stalls easily), or at the very least wastes fuel. The carb is in charge of getting the mixture just right.

On new cars, fuel injection is becoming nearly universal because it provides better fuel efficiency and lower emissions. But nearly all older cars, and all small equipment like lawn mowers and chain saws, use carbs because they are simple and inexpensive.

Inside a Carburetor:

2.Chainsaw Carburetor

1.Chainsaw Carburetor

The carburetor on a chain saw is a good example because it is so straightforward. The carb on a chain saw is simpler than most carbs because it really has only three situations that it has to cover:
*It has to work when you are trying to start the engine cold.
*It has to work when the engine is idling.
*It has to work when the engine is wide open.

No one operating a chain saw is really interested in any gradations between idle and full throttle, so incremental performance between these two extremes is not very important. In a car the many gradations are important, and this is why a car's carb is a lot more complex.

Chainsaw carburetor:
     Here are the parts of a carb:
A carburetor is essentially a tube.
There is an adjustable plate across the tube called the throttle plate that controls how much air can flow through the tube. You can see this circular brass plate in photo 2.
At some point in the tube there is a narrowing, called the venturi, and in this narrowing a vacuum is created. The venturi is visible in photo 1
In this narrowing there is a hole, called a jet, that lets the vacuum draw in fuel. You can see the jet on the left side of the venturi in photo 1.

On the step, learn about carburetor tuning and find out why it's so important.

Carburetor Tuning:
          The carb is operating "normally" at full throttle. In this case the throttle plate is parallel to the length of the tube, allowing maximum air to flow through the carb. The air flow creates a nice vacuum in the venturi and this vacuum draws in a metered amount of fuel through the jet. You can see a pair of screws on the right top of the carb in photo 2. One of these screws (labeled "Hi" on the case of the chain saw) controls how much fuel flows into the venturi at full throttle.

When the engine is idling, the throttle plate is nearly closed (the position of the throttle plate in the photos is the idle position). There is not really enough air flowing through the venturi to create a vacuum. However, on the back side of the throttle plate there is a lot of vacuum (because the throttle plate is restricting the airflow). If a tiny hole is drilled into the side of the carb's tube just behind the throttle plate, fuel can be drawn into the tube by the throttle vacuum. This tiny hole is called the idle jet. The other screw of the pair seen in photo 2 is labeled "Lo" and it controls the amount of fuel that flows through the idle jet.

Both the Hi and Lo screws are simply needle valves. By turning them you allow more or less fuel to flow past the needle. When you adjust them you are directly controlling how much fuel flows through the idle jet and the main jet.

When the engine is cold and you try to start it with the pull cord, the engine is running at an extremely low RPM. It is also cold, so it needs a very rich mixture to start. This is where the choke plate comes in. When activated, the choke plate completely covers the venturi see this video of the choke plate to see it in action). If the throttle is wide open and the venturi is covered, the engine's vacuum draws a lot of fuel through the main jet and the idle jet (since the end of the carb's tube is completely covered, all of the engine's vacuum goes into pulling fuel through the jets). Usually this very rich mixture will allow the engine to fire once or twice, or to run very slowly. If you then open the choke plate the engine will start running normally.

What does a Carburetor Do?
The carburetor has several functions: 1) it combines gasoline and air creating a highly combustible mixture, 2) it regulates the ratio of air and fuel, and 3) it controls the engine's speed.


How a carburetor mixes fuel and air?
When the piston moves down the cylinder on the intake stroke it draws air from the cylinder and intake manifold. A vacuum is created that draws air from the carburetor. The airflow through the carburetor causes fuel to be drawn from the carburetor through the intake manifold past the intake valves and into the cylinder. The amount of fuel mixed into the air to obtain the required air to fuel ratio is controlled by the venturi or choke. When air flows through the venturi its speed increases and the pressure drops. This causes the fuel to be sucked into the air stream from a hole or jet. When the engine is at idle or at rapid acceleration there is not enough air passing through the venturi to draw fuel. To overcome these problems other systems are used.


Delivering gasoline to the carburetor:
Gasoline is delivered to the carburetor by the fuel pump and is stored in the fuel bowl. To keep this level of fuel stored in the bowl constant under all conditions a float system is used. A float operated needle valve and seat at the fuel inlet is used to control the fuel level in the bowl. If the fuel level drops below a certain level the float lowers and opens the valve letting more fuel in. When the float rises it pushes the inlet valve against the seat and shuts off the flow of fuel into the bowl.


Types of carburetors:
There are 3 basic types of carburetors in use today. They are the one barrel, two barrel, and four barrel. Typically, the type of engine and its use will dictate which carburetor is used. In high performance engines multiple carburetors may be used to deliver the amount of fuel required. No matter what type of carburetor your engine uses, National Carburetors is your source for high quality carburetors.


Controlling the speed of the engine:
The throttle controls the speed of the engine by controlling the amount of air fuel allowed in the engine. The throttle is a butterfly valve located after the venturi and is opened by pressing on the gas pedal. The farther the valve is opened the more air/fuel mixture is let into the engine and the faster the engine runs. At low engine speeds when the throttle is only open a little there is not enough air flow to pull in fuel.


Ports
Two ports are used to solve this problem. One port located in the low pressure area and the idle port located below. At low engine speeds both ports draw fuel to keep the engine running. As engine speed increases fuel from the 2 ports decreases until it stops completely.

Handling low speeds:
When the engine is idle there is very little air flowing through the venturi because the throttle valve is closed. The idle port allows the engine to operate under this condition. Fuel is forced through the idle port because of a pressure differential between air in the fuel bowl and vacuum below the throttle valve. Idle fuel mixture is controlled by an adjustable needle valve.


Handling high speeds

Clutch

                                                                     Clutch
If you drive a manual transmission car, you may be surprised to find out that it has more than one clutch. And it turns out that folks with automatic transmission cars have clutches, too. In fact, there are clutches in many things you probably see or use every day: Many cordless drills have a clutch, chain saws have a centrifugal clutch and even some yo-yos have a clutch.

In this article, you'll learn why you need a clutch, how the clutch in your car works and find out some interesting, and perhaps surprising, places where clutches can be found.

Engine without Connecting to Gear Box

Engine Connecting with GearBox

Clutches are useful in devices that have two rotating shafts. In these devices, one of the shafts is typically driven by a motor or pulley, and the other shaft drives another device. In a drill, for instance, one shaft is driven by a motor and the other drives a drill chuck. The clutch connects the two shafts so that they can either be locked together and spin at the same speed, or be decoupled and spin at different speeds.

In a car, you need a clutch because the engine spins all the time, but the car's wheels do not. In order for a car to stop without killing the engine, the wheels need to be disconnected from the engine somehow. The clutch allows us to smoothly engage a spinning engine to a non-spinning transmission by controlling the slippage between them.

To understand how a clutch works, it helps to know a little bit about friction, which is a measure of how hard it is to slide one object over another. Friction is caused by the peaks and valleys that are part of every surface -- even very smooth surfaces still have microscopic peaks and valleys. The larger these peaks and valleys are, the harder it is to slide the object. You can learn more about friction in How Brakes Work.

A clutch works because of friction between a clutch plate and a flywheel. We'll look at how these parts work together in the next section.

Fly Wheel,Clutch Plates:
      In a car's clutch, a flywheel connects to the engine, and a clutch plate connects to the transmission.

When your foot is off the pedal, the springs push the pressure plate against the clutch disc, which in turn presses against the flywheel. This locks the engine to the transmission input shaft, causing them to spin at the same speed.

The amount of force the clutch can hold depends on the friction between the clutch plate and the flywheel, and how much force the spring puts on the pressure plate. The friction force in the clutch works just like the blocks described in the friction section of How Brakes Work, except that the spring presses on the clutch plate instead of weight pressing the block into the ground.
               When the clutch pedal is pressed, a cable or hydraulic piston pushes on the release fork, which presses the throw-out bearing against the middle of the diaphragm spring. As the middle of the diaphragm spring is pushed in, a series of pins near the outside of the spring causes the spring to pull the pressure plate away from the clutch disc (see below). This releases the clutch from the spinning engine.
Clutch plate

Note the springs in the clutch plate. These springs help to isolate the transmission from the shock of the clutch engaging.

This design usually works pretty well, but it does have a few drawbacks. We'll look at common clutch problems and other uses for clutches in the following sections.

Common Problems:
      From the 1950s to the 1970s, you could count on getting between 50,000 and 70,000 miles from your car's clutch. Clutches can now last for more than 80,000 miles if you use them gently and maintain them well. If not cared for, clutches can start to break down at 35,000 miles. Trucks that are consistently overloaded or that frequently tow heavy loads can also have problems with relatively new clutches.

The most common problem with clutches is that the friction material on the disc wears out. The friction material on a clutch disc is very similar to the friction material on the pads of a disc brake or the shoes of a drum brake -- after a while, it wears away. When most or all of the friction material is gone, the clutch will start to slip, and eventually it won't transmit any power from the engine to the wheels.

The clutch only wears while the clutch disc and the flywheel are spinning at different speeds. When they are locked together, the friction material is held tightly against the flywheel, and they spin in sync. It's only when the clutch disc is slipping against the flywheel that wearing occurs. So, if you are the type of driver who slips the clutch a lot, you'll wear out your clutch a lot faster.

Sometimes the problem is not with slipping, but with sticking. If your clutch won't release properly, it will continue to turn the input shaft. This can cause grinding, or completely prevent your car from going into gear. Some common reasons a clutch may stick are:
          Broken or stretched clutch cable - The cable needs the right amount of tension to push and pull effectively.
Leaky or defective slave and/or master clutch cylinders - Leaks keep the cylinders from building the necessary amount of pressure.
           Air in the hydraulic line - Air affects the hydraulics by taking up space the fluid needs to build pressure.
           Misadjusted linkage - When your foot hits the pedal, the linkage transmits the wrong amount of force.
Mismatched clutch components - Not all aftermarket parts work with your clutch.

A "hard" clutch is also a common problem. All clutches require some amount of force to depress fully. If you have to press hard on the pedal, there may be something wrong. Sticking or binding in the pedal linkage, cable, cross shaft, or pivot ball are common causes. Sometimes a blockage or worn seals in the hydraulic system can also cause a hard clutch.

Another problem associated with clutches is a worn throw-out bearing, sometimes called a clutch release bearing. This bearing applies force to the fingers of the spinning pressure plate to release the clutch. If you hear a rumbling sound when the clutch engages, you might have a problem with the throw-out.

In the next section, we'll examine some different types of clutches and how they are used.

Types of Clutches:
There are many other types of clutches in your car and in your garage.

An automatic transmission contains several clutches. These clutches engage and disengage various sets of planetary gears. Each clutch is put into motion using pressurized hydraulic fluid. When the pressure drops, springs cause the clutch to release. Evenly spaced ridges, called splines, line the inside and outside of the clutch to lock into the gears and the clutch housing. You can read more about these clutches in How Automatic Transmissions Work.

An air conditioning compressor in a car has an electromagnetic clutch. This allows the compressor to shut off even while the engine is running. When current flows through a magnetic coil in the clutch, the clutch engages. As soon as the current stops, such as when you turn off your air conditioning, the clutch disengages.

Most cars that have an engine-driven cooling fan have a thermostatically controlled viscous clutch -- the temperature of the fluid actually drives the clutch. This clutch is positioned at the hub of the fan, in the airflow coming through the radiator. This type of clutch is a lot like the viscous coupling sometimes found in all-wheel drive cars. The fluid in the clutch gets thicker as it heats up, causing the fan to spin faster to catch up with the engine rotation. When the car is cold, the fluid in the clutch remains cold and the fan spins slowly, allowing the engine to quickly warm up to its proper operating temperature.

Many cars have limited slip differentials or viscous couplings, both of which use clutches to help increase traction. When your car turns, one wheel spins faster than the other, which makes the car hard to handle. The slip differential makes up for that with the help of its clutch. When one wheel spins faster than the others, the clutch engages to slow it down and match the other three. Driving over puddles of water or patches of ice can also spin your wheels. You can learn more about differentials and viscous couplings in How Differentials Work.

Gas-powered chain saws and weed eaters have centrifugal clutches, so that the chains or strings can stop spinning without you having to turn off the engine. These clutches work automatically through the use of centrifugal force. The input is connected to the engine crankshaft. The output can drive a chain, belt or shaft. As the rotations per minute increase, weighted arms swing out and force the clutch to engage. Centrifugal clutches are also often found in lawn mowers, go-karts, mopeds and mini-bikes. Even some yo-yos are manufactured with centrifugal clutches.

Clutches are valuable and necessary to a number of applications.
           Here some of the links to know how clutch works
                            http://www.youtube.com/watch?v=FfjGohWy-OU
                           http://www.youtube.com/watch?v=c8qsS2g_IiU

                                                           Published by Ravindra,Mechanical

Steering Mechanism

                                                        Steering Mechanism
             
          You know that when you turn the steering wheel in your car, the wheels turn. Cause and effect, right? But a lot of interesting stuff goes on between the steering wheel and the tires to make this happen.

In this article, we'll see how the two most common types of car steering systems work: rack-and-pinion and recirculating-ball steering. Then we'll examine power steering and find out about some interesting future developments in steering systems, driven mostly by the need to increase the fuel efficiency of cars. But first, let's see what you have to do turn a car. It's not quite as simple as you might think!

Turning the Car:
                     You might be surprised to learn that when you turn your car, your front wheels are not pointing in the same direction.

For a car to turn smoothly, each wheel must follow a different circle. Since the inside wheel is following a circle with a smaller radius, it is actually making a tighter turn than the outside wheel. If you draw a line perpendicular to each wheel, the lines will intersect at the center point of the turn. The geometry of the steering linkage makes the inside wheel turn more than the outside wheel.

Rack-Pinion Steering:
                          Rack-and-pinion steering is quickly becoming the most common type of steering on cars, small trucks and SUVs. It is actually a pretty simple mechanism. A rack-and-pinion gearset is enclosed in a metal tube, with each end of the rack protruding from the tube. A rod, called a tie rod, connects to each end of the rack.

The pinion gear is attached to the steering shaft. When you turn the steering wheel, the gear spins, moving the rack. The tie rod at each end of the rack connects to the steering arm on the spindle (see diagram above).

The rack-and-pinion gearset does two things:
It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels.
It provides a gear reduction, making it easier to turn the wheels.

On most cars, it takes three to four complete revolutions of the steering wheel to make the wheels turn from lock to lock (from far left to far right).

The steering ratio is the ratio of how far you turn the steering wheel to how far the wheels turn. For instance, if one complete revolution (360 degrees) of the steering wheel results in the wheels of the car turning 20 degrees, then the steering ratio is 360 divided by 20, or 18:1. A higher ratio means that you have to turn the steering wheel more to get the wheels to turn a given distance. However, less effort is required because of the higher gear ratio.

Generally, lighter, sportier cars have lower steering ratios than larger cars and trucks. The lower ratio gives the steering a quicker response -- you don't have to turn the steering wheel as much to get the wheels to turn a given distance -- which is a desirable trait in sports cars. These smaller cars are light enough that even with the lower ratio, the effort required to turn the steering wheel is not excessive.

Some cars have variable-ratio steering, which uses a rack-and-pinion gearset that has a different tooth pitch (number of teeth per inch) in the center than it has on the outside. This makes the car respond quickly when starting a turn (the rack is near the center), and also reduces effort near the wheel's turning limits.

Rack Pinon Mechanism

Power Rack-and-pinion:
When the rack-and-pinion is in a power-steering system, the rack has a slightly different design.

Part of the rack contains a cylinder with a piston in the middle. The piston is connected to the rack. There are two fluid ports, one on either side of the piston. Supplying higher-pressure fluid to one side of the piston forces the piston to move, which in turn moves the rack, providing the power assist.

We'll check out the components that provide the high-pressure fluid, as well as decide which side of the rack to supply it to, later in the article. First, let's take a look at another type of steering.

Decirculating Steering Mechanism:

Recirculating-ball steering is used on many trucks and SUVs today. The linkage that turns the wheels is slightly different than on a rack-and-pinion system.

The recirculating-ball steering gear contains a worm gear. You can image the gear in two parts. The first part is a block of metal with a threaded hole in it. This block has gear teeth cut into the outside of it, which engage a gear that moves the pitman arm (see diagram above). The steering wheel connects to a threaded rod, similar to a bolt, that sticks into the hole in the block. When the steering wheel turns, it turns the bolt. Instead of twisting further into the block the way a regular bolt would, this bolt is held fixed so that when it spins, it moves the block, which moves the gear that turns the wheels.
           Instead of the bolt directly engaging the threads in the block, all of the threads are filled with ball bearings that recirculate through the gear as it turns. The balls actually serve two purposes: First, they reduce friction and wear in the gear; second, they reduce slop in the gear. Slop would be felt when you change the direction of the steering wheel -- without the balls in the steering gear, the teeth would come out of contact with each other for a moment, making the steering wheel feel loose.

Power Steering:
               Power steering in a recirculating-ball system works similarly to a rack-and-pinion system. Assist is provided by supplying higher-pressure fluid to one side of the block.
Now let's take a look at the other components that make up a power-steering system.

There are a couple of key components in power steering in addition to the rack-and-pinion or recirculating-ball mechanism.


*Pump:
           The hydraulic power for the steering is provided by a rotary-vane pump (see diagram below). This pump is driven by the car's engine via a belt and pulley. It contains a set of retractable vanes that spin inside an oval chamber.

As the vanes spin, they pull hydraulic fluid from the return line at low pressure and force it into the outlet at high pressure. The amount of flow provided by the pump depends on the car's engine speed. The pump must be designed to provide adequate flow when the engine is idling. As a result, the pump moves much more fluid than necessary when the engine is running at faster speeds.

The pump contains a pressure-relief valve to make sure that the pressure does not get too high, especially at high engine speeds when so much fluid is being pumped.


*Rotary Valve:
                     A power-steering system should assist the driver only when he is exerting force on the steering wheel (such as when starting a turn). When the driver is not exerting force (such as when driving in a straight line), the system shouldn't provide any assist. The device that senses the force on the steering wheel is called the rotary valve.

The key to the rotary valve is a torsion bar. The torsion bar is a thin rod of metal that twists when torque is applied to it. The top of the bar is connected to the steering wheel, and the bottom of the bar is connected to the pinion or worm gear (which turns the wheels), so the amount of torque in the torsion bar is equal to the amount of torque the driver is using to turn the wheels. The more torque the driver uses to turn the wheels, the more the bar twists.

The input from the steering shaft forms the inner part of a spool-valve assembly. It also connects to the top end of the torsion bar. The bottom of the torsion bar connects to the outer part of the spool valve. The torsion bar also turns the output of the steering gear, connecting to either the pinion gear or the worm gear depending on which type of steering the car has.

                                                                            Published by Ravindra,Mechanical

                                                           

Top 5 Ways To Improve Engine Response

                          The roads where I live handle a lot of agricultural traffic. Following a trailer off the pig farm is great the first few times ("Aww! Piggies!"), but pig trucks aren't known for their speed, and when you think about where those pigs are going, it's hard to feel right about squealing over how cute they are ("Aww! Pre-bacon!"). Passing the pig trucks, however, is tricky for me. Usually by the time my car realizes that I'd like it to increase its speed sometime this week, a chicken truck is barreling toward me in the passing lane. And since I don't want to play chicken with a chicken truck, I tuck back in behind the pig truck. Driving along in a cloud of Eau de Swine, I think about how I really need to improve my car's engine response.

Whether you're stuck behind a pig truck or just trying to jump off the line at a red light, improved engine response is a good thing. Before we get into how to get it, here's a tip: What most people call engine response, car geeks call throttle response. Why? Because engine response is how quickly the engine modulates its output when the driver increases or decreases pressure on the throttle. Engine responsiveness is how most of us think of it, but if you're talking cars with a snotty guy in a BMW jacket, calling it throttle response will save you from getting a lot of condensation thrown your way. Plus, it's more specific. Engines are complex pieces of machinery, and what we're talking about when we say engine response centers around systems directly related to the throttle. And, since you request and feel engine response through the accelerator (or throttle, if that guy in the BMW jacket is still hanging around), calling it throttle response keeps you focused on what you're asking your car to do, and how well it does it.

1.Caught It Up:
                          Following a trailer off the pig farm is great the first few times ("Aww! Piggies!"), but pig trucks aren't known for their speed, and when you think about where those pigs are going, it's hard to feel right about squealing over how cute they are ("Aww! Pre-bacon!"). Passing the pig trucks, however, is tricky for me. Usually by the time my car realizes that I'd like it to increase its speed sometime this week, a chicken truck is barreling toward me in the passing lane. And since I don't want to play chicken with a chicken truck, I tuck back in behind the pig truck. Driving along in a cloud of Eau de Swine, I think about how I really need to improve my car's engine response.

Whether you're stuck behind a pig truck or just trying to jump off the line at a red light, improved engine response is a good thing. Before we get into how to get it, here's a tip: What most people call engine response, car geeks call throttle response. Why? Because engine response is how quickly the engine modulates its output when the driver increases or decreases pressure on the throttle. Engine responsiveness is how most of us think of it, but if you're talking cars with a snotty guy in a BMW jacket, calling it throttle response will save you from getting a lot of condensation thrown your way. Plus, it's more specific. Engines are complex pieces of machinery, and what we're talking about when we say engine response centers around systems directly related to the throttle. And, since you request and feel engine response through the accelerator (or throttle, if that guy in the BMW jacket is still hanging around), calling it throttle response keeps you focused on what you're asking your car to do, and how well it does it.

One of the easiest ways to improve engine and throttle response is by making sure your fuel filter is clean. When you stomp on the gas pedal, it sends a signal for more fuel to go into the engine. To get there, it has to pass through the fuel filter (which filters out impurities and sediment, keeping your engine clean). Asking and engine with a clogged or dirty fuel filter to respond to throttle input is like asking someone to sprint with a muddy towel over their nose and mouth. They can probably do it, but it won't be pretty.

In addition to poor engine response, symptoms of a clogged fuel filter include rough idling, poor fuel economy, trouble starting, sputtering and flat-out stopping. Cleaning a fuel filter is pretty easy, though. Most cars have their filters in the fuel lines between the fuel pump and the injectors. Because they're made to be cleaned and replaced (if they're really dirty), it's fairly easy to pull a fuel filter from your car's engine. You can clean it by blowing some compressed air on it until air flows through it freely. But if you can't get air to flow through it, it's time for a replacement. Put your dirty fuel filter back in for one last trip to the auto parts store. Playing taps as you throw it away is optional.

2.Get Pumped:
                        If you know your fuel filter is squeaky clean and your car is still about as easy to move as a narcoleptic elephant, you might want to check your fuel pump. When you hit the gas, your fuel pump is supposed to pump fuel (shocking, we know) to the engine. If it isn't working, your engine isn't getting the fuel it needs and won't respond like it should.

Most cars today use an electric fuel pump (but if your car has a carbureted engine, it will likely have a mechanical fuel pump). There are two types of electric fuel pumps: suction type and pusher-type. True to their name, sucker-type fuel pumps suck fuel from the tank by creating a vacuum. Pusher-type pumps are placed in a car's gas tank and push gas to the engine. They should really try to make these pump names less complex.

Unlike a fuel filter, fuel pump problems are harder to fix. You're probably going to need to take your car to a mechanic, and oftentimes the only solution to a bad fuel pump is to replace it. But, considering that your fuel pump is the mechanism that delivers the food to your engine's waiting mouth, replacement is worth it. Even if your car runs with decreased engine response due to a faulty fuel pump, it's probably just a matter of time before that fuel pump fully shuffles off its mortal coil, stranding you somewhere you'd rather not be.

3.Do Some Lines:
                            still about as easy to move as a narcoleptic elephant, you might want to check your fuel pump. When you hit the gas, your fuel pump is supposed to pump fuel (shocking, we know) to the engine. If it isn't working, your engine isn't getting the fuel it needs and won't respond like it should.

Most cars today use an electric fuel pump (but if your car has a carbureted engine, it will likely have a mechanical fuel pump). There are two types of electric fuel pumps: suction type and pusher-type. True to their name, sucker-type fuel pumps suck fuel from the tank by creating a vacuum. Pusher-type pumps are placed in a car's gas tank and push gas to the engine. They should really try to make these pump names less complex.

Unlike a fuel filter, fuel pump problems are harder to fix. You're probably going to need to take your car to a mechanic, and oftentimes the only solution to a bad fuel pump is to replace it. But, considering that your fuel pump is the mechanism that delivers the food to your engine's waiting mouth, replacement is worth it. Even if your car runs with decreased engine response due to a faulty fuel pump, it's probably just a matter of time before that fuel pump fully shuffles off its mortal coil, stranding you somewhere you'd rather not be.

If you don't get by now that the best way to improve engine response is to make sure that the engine is getting plenty of fuel, then reading the rest of this probably won't help you. But, if you're cool with the whole "engine needs fuel" concept, there's someplace else you should look for problems with your engine response: your fuel lines.

The fuel pump sends fuel from the gas tank to the engine, but that fuel has to get there somehow. That's where the fuel lines come in. A leak or a kink in your fuel lines, even a tiny one, can rob your engine of performance. Because the fuel lines won't be able to maintain the pressure needed to transport the fuel through the lines, a car with a leaky fuel line won't respond quickly to driver inputs. The fuel lines are like train tracks: If there's a problem with the tracks, the train won't be coming through -- at least not a full speed.

If you have a big leak in your fuel lines, you'll probably know it because there'll be a puddle of fuel under your car when it's parked. A smaller leak or a kink in a line will be harder to detect, however. You visually inspect the lines or check fuel pressure using a...wait for it...fuel pressure gauge. That sort of test can be a bit much for people who aren't dedicated mechanics, and messing with fuel lines raises some safety issues. If you're not completely sure you can safely do the fuel pressure test and fix any problems you find, you're next step should be pulling out the yellow pages and finding a good mechanic.

4.Sense The Problem:
                                 Sometimes what's robbing your engine response isn't mechanical or fuel related. It could be a sensor problem. Most late-model cars regulate engine performance through a central computer. That computer uses sensors to look at driver inputs and engine conditions. It then directs various components based on the current conditions and what the driver is asking the car to do. If the sensors are bad, your car's computer is flying blind. It's kind of like blindfolding someone and then plopping them down in the middle of a marching band performance. You can help by shouting instructions, but because they won't be aware of all the conditions, they'll run amuck pretty quickly (Author's note: I'd pay to see something like this). A computer with bad sensors only has the driver's inputs to go on.

Two main sensors are usually the culprits for bad engine responsiveness: the mass air flow sensor and the engine speed sensor. The mass air flow sensor (MAF) measures and reports on the airflow into the engine so the computer can request the appropriate amount of fuel. If the MAF is bad, the engine won't be getting the correct amount of fuel, which will throw off the engine's combustion (we're talking about internal combustion engines, after all) and decrease engine response.

Though it sounds like it measures how fast you're going, the engine speed sensor actually measures how fast the engine's crankshaft is spinning. Just like you need a certain amount of air and calories to perform a given physical task, your car's engine needs a specific amount of air and fuel to operate at various engine speeds. If the computer doesn't know how fast the engine is working, it won't know how much air or fuel to send to it and the engine will lose responsiveness.

Diagnosing a sensor problem is usually fairly easy. A mechanic simply hooks up a diagnostic code reader to the car and is told which sensor needs fixing. You can get a code reader for home use too, though replacing a sensor at home can be a little tricky. Still, having your own code reader can make for some fun dinner party conversation, provided you get people's permission to diagnose their cars and don't just approach people and smirk that you have a MAF problem for them to solve.

5.Open The Pod Body Doors,HAL:
                                   You know how your car has that central computer tracking everything and keeping your engine running optimally? Do you ever feel like that computer might just be a little evil?

We tend to think people trump computers. Except when it comes to spell check. And doing any sort of math. But when it comes to cars, we really tend to think that the driver knows best. In modern cars, however, that's not always true. The computer that runs your car may be intentionally dampening engine response. That makes autocorrect seem almost benign, doesn't it?

There's actually a good reason your car's computer might be limiting engine response. Fuel economy is the biggest one. Hard acceleration is one of the biggest fuel drains on the road. By dampening engine response, the computer can save fuel. That saves you cash and also gets the car a better fuel economy rating. Since car companies have to hit a certain average fuel economy rate for all their models, limiting engine response benefits them as well. In some cases, however, the electronic throttle control systems on some cars are just not well-engineered, leading to poor engine response and delays between the driver's request for more engine power and the car actually delivering it.

If you want better engine response, having a nannying C3PO on-board is a problem with only one solution: Find an R2 unit that will let you have some fun. Aftermarket plug-and-play units are available for many cars and can improve throttle response. These are little computers that plug into your car, intercept the signal from the throttle and send a more aggressive one to the computer. You can also customize the computers on many cars, setting the engine to respond just as you like it.

                                                                                                        Published by Ravindra,Mechanical

 

Top 5 Engine Modifications

For some auto enthusiasts, the car that rolls off of the assembly line isn't quite up to speed, so to speak. Some drivers love to tinker with their cars' engines, adding more power or improving fuel-efficiency. But what can you do when you want to feel a little more rumbling coming from that engine?

Ordinarily, an engine handles air intake this way: A piston moves down, creating a vacuum, allowing air at atmospheric pressure to be drawn into the combustion chamber. Combined with fuel, it forms a unit of energy, which is turned into kinetic energy (or horsepower) via combustion, thanks to an ignition from the spark plug.

To improve a car's performance -- in other words, to make it go faster, something all car aficionados and gearheads crave -- would require more powerful, or at least more efficient, combustion. More fuel alone going into the engine wouldn't work, because of the delicate relationship between the oxygen in the air and the fuel required for the combustion. Instead, modifying your car's engine to accept more air and fuel is the key. Here are five ways to modify your car to make that happen.

1.Superchargers:
                    A supercharger pressurizes air intake to above the normal atmospheric level so that more air can go into the engine, thus combining it with more fuel to produce more power. Powered mechanically via a belt or chain from the crankshaft, a supercharger spins at a rate of at least 50,000 RPM (faster than the engine itself) in order to force air into the combustion chamber. This makes space for more fuel, which creates for a larger combustion.

How much more energy is produced? Nearly 50 percent more horsepower, if everything is installed correctly. Attaching one to the engine of a normal sized car will immediately make it behave like a much larger, more powerful vehicle. What's great is that it can be a do-it-yourself project -- simply bolt it to the top or side of the engine and follow the manufacturer's installation instructions.

2.Air Filters:
                             Aftermarket air filters allow for more airflow into the engine for a more efficient use of the air/fuel combination, while also blocking contaminants and impurities that slowly degrade performance over time. Secondary air filters are generally made up of a thin layer of cotton or other material housed between several layers of impurity-catching thin mesh. High-quality aftermarket air filters (versus the standard, paper-based ones that come straight from the factory) drop into the engine's air box, and that's about it for installation. And because they're made of fabric, they're washable, making for an inexpensive, reusable performance enhancer.

3.Cold Air Intake Kit:
                                 Although it might seem like a small thing, the temperature of the air can affect the efficiency of your car. A cold air intake kit is an aftermarket system that brings cool air into the internal combustion engine. Normally, a car regulates the temperature of air as it enters the engine, providing warm air when the engine is cold, and cold air when the engine is warm. Cold air intake kits, however, can lead to higher performance and engine efficiency, based on the idea that colder air is denser than warm air, which means that it contains more of that necessary oxygen for a more dynamic combustion in the engine.

4.Performance Chips:
                          If you drive a late-model car, it's highly likely that there's an onboard computer regulating things and running the show, controlling such functions as timing, anti-lock brakes and the all-important fuel-to-air ratio. Performance chips (or superchips) are "hacks" that can be installed to override factory settings, and they're most attractive to gearheads since they can increase the power of the engine and horsepower. A performance chip sets new parameters for the functions of your choosing, such as telling your car's engine to use gas slightly more efficiently, or to intake more air for a bigger combustion. Installation is easy and DIY -- once you acquaint yourself with your car's electronics, simply take out the factory chip and plug in the new one, just like plugging in a chip in a desktop computer.


5.Weight Reduction:
                       Lightweight things move faster than heavier things -- that's as basic as physics can get. This solution is simultaneously low-tech and work intensive, in that it involves switching out heavier parts of the car (throughout the car, not just in the engine block) with lighter parts so as to make the car lighter and more aerodynamic. There are a lot of options: get rid of extra seats you don't use if you don't cart a lot of people around; replace glass windows with lighter plastic or acrylic versions; or even remove parts of the dashboard. Disc brakes even offer significant weight difference over traditional brakes.

                                                                                                          Published by Ravindra,Mechanical

Top 10 Improvements In Engine Design

                    Most people know that the Ford Model T was the first truly affordable automobile. But do you know what kind of engine it had? The original Model T, released in 1908, packed a 2.9-liter four-cylinder engine with just 22 horsepower. That's a tiny output for its size compared to the engines of today, but it sure beat the engine in what's considered to be the first automobile -- the 1885 Benz Patent Motorwagen. That car had a single-piston engine and generated just two-thirds of a single horsepower. As you can see, automobile engines have been in constant evolution since the very beginning of motoring. Today they are more powerful, quieter, more durable, less polluting and more fuel-efficient than they have ever been before, thanks to constant advancements in engine design and technology. Automotive engineers are constantly working on ways to improve the internal combustion engine and carry it into the future. How many other inventions do you know that have been continuously refined for more 150 years? In this article, we'll take a look at 10 of the biggest and most significant engine improvements of all time. From fuel injection to hybrid motors, we'll take a look at where engines have been, and hopefully get some insight on where they're headed.

1.The Four Stroke Engine:

Benefits: More fuel-efficient, less polluting
Drawbacks: More complicated, more expensive to manufacture

Remember that Benz Patent Motorwagen we talked about? In addition to having a single piston, or cylinder, it was a two-stroke engine, like many early motors. Stroke refers to the movement of the piston in the engine.

Four-stroke engines were one of the earliest improvements made to internal combustion engines in the late 1800s. On a four-stroke engine, there are four steps the engine takes as it burns gasoline: intake, compression, power, and exhaust [source: CompGoParts.com]. These steps all occur when as piston moves up and down two times.

Earlier, simpler two-stroke engines accomplish the same task -- burning gasoline to create mechanical motion -- but they do it in two steps. Today, two-stroke engines are found on small equipment like lawnmowers, small motorcycles, and large, industrial engines. Nearly all cars use the four-stroke cycle.

Four-stroke engines carry several benefits, including improved fuel economy, more durability, more power and torque, and cleaner emissions. However, compared to two-stroke engines, they are more complicated and expensive to make, and require the use of valves for the intake and exhaust of gases.

In spite of this, four-stroke engines have become the industry standard for cars, and they likely aren't going away any time soon. We'll learn more about the role of valves and how they've been improved upon later in this article.

2.Forced Induction:

Benefits: More power without an increase in engine size
Drawbacks: Fuel consumption, turbo lag

An engine requires three things to generate motion: fuel, air, and ignition. Cramming more air into an engine will increase the power generated by the engine's pistons. A long-standing way to do that, and one that's becoming increasingly popular as of late, is to use forced induction. You may know this process better by the parts that do make it happen -- turbochargers and superchargers.

In a forced induction engine, air is forced into the combustion chamber at a higher pressure than usual, creating a higher compression and more power from each stroke of the engine [source: Bowman]. Turbochargers and superchargers are essentially air compressors that shove more air into the engine.

Forced induction systems were used on aircraft engines long before they started being added to car engines in the 1960s. They are especially beneficial for small engines as they can generate a lot of extra power without increasing the engine's size or causing a dramatic drop in fuel economy.

A good example is the turbocharged Mini Cooper S, which only has a 1.6-liter engine but produces more than 200 horsepower in some applications. In addition, high-performance cars like the Porsche 911 Turbo or Corvette ZR-1 use forced induction to achieve tremendous gains in power.

The drawbacks? Cars that have turbochargers often require premium gasoline. Then there's the issue of turbo lag, where the power gains aren't felt until the turbocharger spools up at higher revolutions per minute (RPM). Engineers have helped reduce both of those drawbacks in recent years.

And with fuel economy and emissions standards getting stricter, many carmakers are turning to forced induction on smaller engines instead of building larger engines. On the newest Hyundai Sonata, for example, the top engine one can buy is no longer a V6, but a turbo four-cylinder.

Next up, we'll discuss why carburetors have practically become a thing of the past thanks to fuel injection.

3.Fuel Injection:

Benefits: Better throttle response, increased fuel efficiency, more power, easier starting
Drawbacks: More complexity and potentially expensive repairs

For decades, the preferred method for mixing fuel and air and depositing it into the engine's combustion chamber was the carburetor. Press the accelerator pedal to full throttle, and the carburetor allows more air and fuel into the engine.

Since the late 1980s, carburetors have been almost completely replaced by fuel injection, a far more sophisticated and effective system of mixing fuel and air. Fuel injectors spray gasoline into the air intake manifold, where fuel and air mix together into a fine mist. That mix is brought into the combustion chamber by valves on each cylinder during the intake process. The engine's on-board computer controls the fuel injection process.

So why did fuel injection replace the carburetor? To put it simply, fuel injection just works better in every aspect. Computer-controlled fuel-injected engines are easier to start, especially on cold days, when carburetors could make things tricky. Engines with fuel injection are also more efficient and more responsive to changes in the throttle [source: Automedia].

They do have drawbacks in terms of their increased complexity. Fuel injection systems are more costly to repair than carburetors as well. However, they have become the industry standard for fuel delivery, and it doesn't look like carburetors will be making a comeback anytime soon.

In this next section, we'll discuss the next step in fuel injection technology known as direct injection.

4.Direct Injection:

Benefits: More power, better fuel economy
Drawbacks: More expensive to make, relatively new technology

Direct injection is a further refinement of the improvements made by fuel injection. As you may have guessed from its name, it allows fuel injection to "skip a step," which adds efficiency to the engine, and more power and improved fuel economy as a consequence.

On a direct injection engine, fuel is sprayed directly into the combustion chamber, not into the air intake manifold. Engine computers then make sure the fuel is burned exactly when and where it is needed, reducing waste. Direct injection provides a leaner mix of fuel, which burns more efficiently. In some ways it makes gasoline-powered engines more similar to diesel engines, which have always used a form of direct injection.

As we learned earlier, direct injection engines boast an increase in power and fuel economy over stand fuel injection systems. But they have their drawbacks as well. For one, the technology is a relatively new one, having come to market only in the last decade or so. More and more companies are starting to increase their use of direct injection, but it has yet to become the standard.

Sometimes, direct injection engines can exhibit the buildup of carbon deposits on the intake valves, which could cause reliability issues. Some car tuners have expressed difficulty with modifying direct injection engines as well. Despite these issues, direct injection is the hot new technology in the automotive world right now. Expect to see it on more and more cars as time goes on.

Next, let's look at the use of aluminum engine blocks vs. old-school iron blocks.

5.Aluminium Engine Blocks:
Benefits: Lighter weight leads to more efficiency and better handling
Drawbacks: Can warp at high temperatures

Over the past few years, cars have been trending towards being more lightweight in many ways. Automakers look for ways to reduce a vehicle's weight in order to generate better fuel economy and performance. One of the ways they've done that is largely by replacing engines made of iron with aluminum ones.

For many years, iron engine blocks were the industry standard. Today the majority of all new small engines use aluminum instead, though many large V8 engines still use iron blocks. Aluminum weighs far less than iron -- typically, an aluminum engine weighs half what an iron one weighs. That translates into an overall lighter weight for the car, which means better handling and more fuel efficiency [source: Murphy].

Aluminum does have some drawbacks, however. As a metal, it's not as strong as iron and doesn't hold up to high levels of heat as well. Many early aluminum block engines had problems with cylinders warping, leading to concerns over durability. Those problems have been largely solved, however, and aluminum has clearly asserted itself as the future of engines due to its weight-saving properties.

In this next section, we'll talk about how camshafts have revolutionized engine design.

6.Over Head CamShafts:
Benefits: Better performance
Drawbacks: Increased complexity

You've probably heard the term "DOHC" or "dual overhead camshafts" when someone talks about an engine. Most people recognize it as a desirable feature to have, but what does it mean? The term refers to the number of overhead camshafts above each cylinder in the engine.

Camshafts are part of your car's valvetrain, which is a system that controls the flow of fuel and air into the cylinders. For many decades cars primarily had OHV engines, meaning overhead valves, also called "pushrods." Pushrods are driven by camshafts inside the engine block. This setup adds mass to the engine and can limit its overall speed.

On an overhead cam setup, the camshaft is much smaller and is inserted above the cylinder head itself, rather than in the engine block. There's one on a single overhead cam (SOHC) engine, while a DOHC engine has two. The benefit to the overhead cam setup is that it allows for more intake and exhaust valves, meaning fuel, air and exhaust can move more freely through the engine, adding power.

While many car companies have done away with pushrod engines, DOHC and SOHC haven't supplanted them quite yet. Chrysler still uses pushrods to generate lots of power for their Hemi V8 engines; General Motors utilizes pushrods on some of their high-tech, modern V8s as well. But DOHC and SOHC engines have been prominent on engines, especially smaller ones, since the 1980s.

The drawback of having overhead cams is that they increase complexity and cost. Are you noticing a trend here yet?

Next we'll learn more still about how valves affect performance when we talk about variable valve timing.

7.Variable Valve Timing:
Benefits: Fuel economy, more flexible power delivery
Drawbacks: Greater cost to produce

If you're at all familiar with Honda engines, you've almost certainly heard the term VTEC. People who tune their Hondas for performance often speak of "VTEC kicking in." But what exactly does that mean?

VTEC refers to variable valve timing and lift electronic control, a form of variable valve timing. There are times when an engine requires more air flow, like during hard acceleration, but a traditional engine often does not allow enough air to flow, resulting in lower performance. Variable valve timing means the flow of air in and out of the valves is slowed down or sped up as needed [source: Autropolis].

Honda is hardly the only car company to offer such a system. Toyota has one they call VVT-i, for variable valve timing with intelligence, and BMW has a system called Valvetronic or VANOS, which stands for variable Nockenwellensteuerung, meaning variable camshaft control. While they all work a little differently, they all accomplish the same task -- allowing more air and fuel into the valves at different speeds. This makes an engine more flexible and allows it to deliver peak performance in a variety of conditions. It also increases fuel economy.

Many engines now incorporate some form of variable valve timing, often controlled by the engine's on-board computer. We'll talk about how engine computers have revolutionized design in this next section.

8.On-Board Engine Computers:
Benefits: Fuel economy, better diagnosis of problems
Drawbacks: Cost, complexity

An engine is an incredibly sophisticated device. It has dozens of moving parts and has scores of different processes taking place at once. That's why modern cars have everything regulated by an on-board computer called an engine control unit, or ECU.

The ECU makes sure processes like ignition timing, the air/fuel mixture, fuel injection, idle speed, and others operate the way they're supposed to. It monitors what's going on in the engine using an array of sensors and performs millions of calculations each second in order to keep everything operating correctly. Other computers in the car control things like electrical systems, airbags, interior temperature, traction control, anti-lock brakes and the automatic transmission.

Cars have become increasingly computerized since the first on-board diagnostic (OBD) computers were added in the 1980s. That's the computer that's responsible for the "check engine" light on your dashboard. A mechanic can plug a computer into the OBD port and get a sense of your car's problem areas. They can't use OBD to immediately know what's wrong with your car, but it gives them a great starting point.

By making the engine run more efficiently, engine computers can result in greater fuel efficiency and easier diagnosis of problems. But they also make engines far more complicated, and can make them tricky for weekend mechanics to work on.

Next up: Let's learn why diesel engines aren't the smoky, noisy, low-power oil burners of the past.

9.Clean Diesel:
Benefits: Torque, fuel economy, cleaner emissions
Drawbacks: Cost of fuel, low RPMs, higher initial cost

We've talked a lot about gasoline engines so far, but what about diesel engines? Diesels have never been big sellers in the United States. Despite their superior fuel economy over similar gas engines, many Americans still think of diesels as the noisy, sooty, smelly, unreliable motors of the 1970s and 1980s.

That's not the case anymore. The modern diesel engine is powerful, clean and extremely fuel-efficient. Today's engines use a low-sulfur form of diesel fuel, and systems within the car help eliminate particle matter and excess pollution.

The diesels made by companies like Volkswagen, Mercedes-Benz, BMW, Volvo and others boast engine improvements like turbocharging, sophisticated fuel injection, and computer control to provide a driving experience that's both efficient and high in torque [source: Bosch].

Diesel engines have some drawbacks, mainly their low RPM level and the higher cost of diesel fuel. But since many of them can achieve well over 40 miles per gallon (17 kilometers per liter) on the highway, the driver will need to pay for that fuel a lot less often. And if you're wondering if modern diesels offer good performance, look no further than the last few 24 Hours of Le Mans races, where Audi has dominated using a diesel racecar.

Finally, we'll look at the current leader in "green" cars -- the hybrid engine.

10.Hybrid Cars:
Benefits: Fuel economy
Drawbacks: Higher initial cost, complexity

A combination of high gas prices, an increased awareness of the environment among drivers, and government regulations raising fuel economy and emissions standards have forced engines to "go green" more than ever before. One of the biggest engine improvements used to boost efficiency in recent years is the hybrid engine.

Hybrids were an obscure a decade ago, but now everyone knows how they work -- an electric motor is partnered with a traditional gasoline engine in order to achieve high fuel economy numbers, but without the "range anxiety" of an electric engine, where the driver always wonders what will happen when a charge runs out.

The Toyota Prius remains the top selling hybrid car in America. It boasts a 1.8-liter four cylinder engine coupled with an electric motor that produces 134 horsepower. At low speeds, the electric engine acts alone, meaning the car does not use gas at all. At other times, it assists the gasoline engine. The whole package gets about 50 miles per gallon (21.3 kilometers per liter) in both the city and the highway [source: AOL Autos].

Hybrids like the Prius represent the latest evolution in internal combustion technology. While their benefits come in the form of fuel efficiency, there are some drawbacks as well. Hybrids have a higher initial cost than their non-hybrid counterparts, and some have argued that gas must be much more expensive than it is now (unbelievable as that may sound) before the driver recoups the extra cost of the hybrid car.

However, it's clear that engines are trending towards reduced emissions and greater fuel-efficiency. While electric-only cars are becoming more common, it's clear the internal combustion engine isn't going anywhere quite yet. It will simply continue to evolve to be better and better, just like it has since the days of the Model

                                                                                                       Published by Ravindra,Mechanical