How a Car Clutch Works

For most who have driven for a few years, you know that there are options to how you are able to control your vehicle.  In most cars, this is the difference between driving a manual or automatic car.  With manual transmission, you can expect to also have to use a car clutch in order to catch your speed and to go to the next gear, while automatic options will take care of the switch in gears for you.  If you are interested in getting a car with a clutch, knowing how it works first will allow you to gain full speed towards driving the way you want to.

The first gear you want to get into when driving a clutch is to understand exactly how it works.  A clutch is in both automatic and manual cars; however, you are in control of when it turns when it is in a manual car.   When you step on the clutch to shift gears, you are actually changing the level of functioning between the engine and the tires.  When the engine starts spinning, it is connected to the wheels in order for both to turn.

 When you gain speed, so does the engine and so do the tires.  If you stay in the same gear, it causes more tension and friction and will kill the tire.  When you push down on the clutch, it releases the tension and changes into a higher gear, which allows the engine and tire to spin together in conjunction with each other.  At some of the higher gears, this is not only causing them to spin together, with a different type of tension, but also releases the spinning from the transmission so that you can move faster without the extra tension. 

With the way that the clutch spins in between the engine, transmission and tires is also the need to watch exactly how it is working.  This is because the clutch works by creating a friction between these three areas.  As it moves, there is a wearing down of the clutch.  This especially happens if the car engine has to work harder or if the gear isn't changed at the same time.  Because of this, you will want to watch the clutch disc that causes the friction.  Without this, the clutch can start to slip and will make it so that you can't switch gears and will cause the engine to die. 

If you want to make sure that your clutch stays in the right gear, you can check to see if the pedal to the clutch is hard to push in or slips down too easily.  This will let you know that the friction on the disc is not working correctly or that it may have slipped.  Getting this fixed as soon as it starts to happen will allow your car to continue to function between and will allow you to stay in the right gear. 

If you are the type that likes to control the speed of the engine and likes to manually switch gears, getting a car that has a clutch is the best option for driving.  Knowing exactly what happens when you switch gears so that you can continue to make a smooth transition will allow you to continue driving up to speed while staying in gear.

Read More

Two Stroke Engine

A two-stroke engine is an internal combustion engine that completes the process cycle in one revolution of the crankshaft (an up stroke and a down stroke of the piston, compared to twice that number for a four-stroke engine). This is accomplished by using the end of the combustion stroke and the beginning of the compression stroke to perform simultaneously the intake and exhaust (or scavenging) functions. In this way, two-stroke engines often provide high specific power, at least in a narrow range of rotational speeds. The functions of some or all of the valves required by a four-stroke engine are usually served in a two-stroke engine by ports that are opened and closed by the motion of the piston(s), greatly reducing the number of moving parts. Gasoline (spark ignition) versions are particularly useful in lightweight (portable) applications, such as chainsaws, and the concept is also used in diesel compression ignition engines in large and weight insensitive applications, such as ships and locomotives.

                                                                Working

Intake

The fuel/air mixture is first drawn into the crankcase by the vacuum that is created during the upward stroke of the piston. The illustrated engine features a poppet intake valve; however, many engines use a rotary value incorporated into the crankshaft.

Crankcase compression

During the downward stroke, the poppet valve is forced closed by the increased crankcase pressure. The fuel mixture is then compressed in the crankcase during the remainder of the stroke.

Transfer/Exhaust

Toward the end of the stroke, the piston exposes the intake port, allowing the compressed fuel/air mixture in the crankcase to escape around the piston into the main cylinder. This expels the exhaust gasses out the exhaust port, usually located on the opposite side of the cylinder. Unfortunately, some of the fresh fuel mixture is usually expelled as well.

Compression

The piston then rises, driven by flywheel momentum, and compresses the fuel mixture. (At the same time, another intake stroke is happening beneath the piston).

Power

At the top of the stroke, the spark plug ignites the fuel mixture. The burning fuel expands, driving the piston downward, to complete the cycle. (At the same time, another crankcase compression stroke is happening beneath the piston.)

Read More

Four Stroke Engine

A four-stroke engine, also known as four-cycle, is an internal combustion engine in which the piston completes four separate strokes—intake, compression, power, and exhaust—during two separate revolutions of the engine's crankshaft, and one single thermodynamic cycle.

                                                                                        Working 

Intake

During the intake stroke, the piston moves downward, drawing a fresh charge of vaporized fuel/air mixture. The illustrated engine features a poppet intake valve which is drawn open by the vacuum produced by the intake stroke. Some early engines worked this way; however, most modern engines incorporate an extra cam/lifter arrangement as seen on the exhaust valve. The exhaust valve is held shut by a spring (not illustrated here).

Compression

As the piston rises, the poppet valve is forced shut by the increased cylinder pressure. Flywheel momentum drives the piston upward, compressing the fuel/air mixture.

Power

At the top of the compression stroke, the spark plug fires, igniting the compressed fuel. As the fuel burns it expands, driving the piston downward.

Exhaust

At the bottom of the power stroke, the exhaust valve is opened by the cam/lifter mechanism. The upward stroke of the piston drives the exhausted fuel out of the cylinder.

Read More

CRDI - Common Rail Direct Injection

CRDI is an intelligent way of controlling a diesel engine with use of modern computer systems. CRDI helps to improve the power, performance and reduce harmful emissions from a diesel engine. Conventional Diesel Engines (non-CRDI engines) are sluggish, noisy and  poor in performance compared to a CRDI engine.
CRDI or common rail direct injection system is also sometimes referred to by many similar or different names. Some brands use name CRDe / DICOR / Turbojet / DDIS / TDI etc. All these systems work on same principles with slight variations and enhancements here and there.
CRDI system uses common rail which is like one single rail or fuel channel which contains diesel compresses at high pressure. This is a called a common rail because there is one single pump which compresses the diesel and one single rail which contains that compressed fuel. In conventional diesel engines, there will be as many pumps and fuel rails as there are cylinders.

As an example, for a conventional 4 cylinder diesel engine there will be 4 fuel-pumps, 4 fuel rails each feeding to one cylinder. In CRDI, there will be one fuel rail for all 4 cylinders so that the fuel for all the cylinders is pressurized at same pressure.
The fuel is injected into each engine cylinder at a particular time interval based on the position of moving piston inside the cylinder. In a conventional non-CRDI system, this interval and the fuel quantity  was determined by mechanical components, but in a CRDI system this time interval and timing etc are all controlled by a central computer or microprocessor based control system.

To run a CRDI system, the microprocessor works with input from multiple sensors. Based on the input from these sensors, the microprocessor can calculate the precise amount of the diesel and the timing when the diesel should be injected inside the cylinder. Using these calculations, the CRDI control system delivers the right amount of diesel at the right time to allow best possible output with least emissions and least possible  wastage of fuel.
The input sensors include Accelerator Pedal Position (APP) sensor, crank position sensor, pressure sensor, lambda sensor etc. The use of sensors and microprocessor to control the engine makes most efficient use of the fuel and also improved the power, fuel-economy and performance of the engine by managing it in a much better way.
One more major difference between a CRDI and conventional diesel engine is the way the fuel Injectors are controlled. In case of a conventional Engine, the fuel injectors are controlled by mechanical components to operate the fuel injectors. Use of these mechanical components adds additional noise as there are many moving components in the injector mechanism of a conventional diesel engine. In case of a CRDI engine, the fuel injectors are operated using solenoid valves which operate on electric current and do not require complex and noisy mechanical arrangement to operate the fuel Injection into the cylinder. The solenoid valves are operated by the central microprocessor of the CRDI control system based on the inputs from the sensors used in the system.
So if I summarize it, CRDI works on intelligently controlling the Diesel Engine by using sensors and microprocessors. It replaces some of the mechanical components with intelligent electrical and electronic systems which improves the power, response, efficiency and performance. It also reduces the noise, emissions and vibration levels to a considerable extent.

Read More

MPFI – Multi-point Fuel Injection

The term MPFI is used to specify a technology used in Gasoline/petrol Engines. For Diesel Engines, there is a similar technology called CRDI. We will discuss CRDI in a separate article to avoid confusion.
MPFI System is a system which uses a small computer (yes, a small computer without keyboard or mouse, its more like a microchip) to control the Car’s Engine. A Petrol car’s engine usually has three or more cylinders or fuel burning zones. So in case of an MPFI engine, there is one fuel –injector installed near each cylinder, that is why they call it Multi-point (more than one points) Fuel Injection.

In plain words, to burn petrol in an Engine to produce power, Petrol has to be mixed with some air, ignited in a cylinder (also called combustion chamber), which produces energy and runs the engine. I will not talk of further internal details because it will make this article for Engineers and not common people.
Before MPFI system was discovered, there was a technology called “Carburetor”. Carburetor was one chamber where petrol and air was mixed in a fixed ratio and then sent to cylinders to burn it to produce power. This system is purely a mechanical machine with little or no intelligence. It was not very efficient in burning petrol, it will burn more petrol than needed at times and will produce more pollution. But with the advancement of technology this was about to change.

MPFI emerged an Intelligent way to do what the Carburetor does. In MPFI system, each cylinder has one injector (which makes it multi-point). Each of these Injectors are controlled by one central car computer. This computer is a small micro-processor, which keeps telling each Injector about how much petrol and at what time it needs to inject near the cylinder so that only the required amount of petrol goes into the cylinder at the right moment.
So the working of MPFI is similar to Carburetor, but in an improved way, because now each cylinder is treated independently unlike Carburetor. But one major Key difference is that MPFI is an intelligent system and Carburetor is not. MPFI systems are controlled by a computer which does lots of calculations before deciding what amount of petrol will go into what cylinder at a particular point in time. It makes that decision based on the inputs it reads.
For the Inputs, the microprocessor (or car’s computer) reads a number of sensors. Through these sensors, the microprocessor knows the temperature of the Engine, the Speed of the Engine, it knows the load on the Engine, it knows how hard you have pressed the accelerator, it knows whether the Engine is idling at a traffic signal or it is actually running the car, it knows the air-pressure near the cylinders, it knows the amount of oxygen coming out of the exhaust pipe.
Based on all these inputs from the sensors, the computer in the MPFI system decides what amount of fuel to inject. Thus it makes it fuel efficient as it knows what amount of petrol should go in. To make things more interesting, the system also learns from the drivers driving habits. Modern car’s computers have memory, which will remember your driving style and will behave in a way so that you get the desired power output from engine based on your driving style. For example, if you have a habit of speedy pick-up, car’s computer will remember that and will give you more power at low engine speeds by putting extra petrol, so that you get a good pick-up. It will typically judge this by the amount of pressure you put on accelerator.
So the cars of today are really intelligent, well not as intelligent as drivers but fairly intelligent to keep pollution under control and saving the fuel.

Read More

What Is CBU And CKD Cars and Bikes ? CBU Vs CKD

Most of the automobile publications use the words like CBU and CKD which may sound quite confusing to many. These terms are more commonly used in terms of the Imported automobile cars and bikes. In this post I will share the meaning of these terms CBU and CKD under as some of the auto basic terms in simple language.

                                                        CBU – Completely Built Unit

Completely built unit is the terminology when a car/bike/automobile is imported/exported to/from some other country as a complete car fully assembled. These automobiles do not require an assembly before they can be sold out to the buyers in the target country’s markets. Most of the imported cars and bikes in India come as a CBU.

 

                                                    CKD – Completely Knocked Down

Completely knocked down car / bike /automobile is one which is imported or exported in parts and not as one assembled unit. Such units are first sent to an assembly plant in the target country where all these parts are assembled and one complete car / bike / vehicle is made using the imported components. These kinds of units generate employment in the target country as more machinery and manpower investment is needed to assemble the components to make the vehicle.

 

  
                                                                                  CBU Vs CKD

CBU and CKD do not differ much in terms of technological sense except for the fact that CBU cars / bikes / vehicles are assembled in the same country where they originate and then exported to the target country. CKD cars / bikes / vehicles are assembled in the target country where all the parts of the vehicles are assembled and then sold to the end customers.
When talking from Indian perspective, CBU and CKD have a sharp difference in the import duties. At present, the import duties on a CBU vehicle coming to India from abroad is liable for an import duty of nearly 110% while the CKD attracts 60% duty. This sharp difference is strategically kept like this because CBU does not create as much of revenues and employment for the target country (India in this case). A CKD when assembled in the target country requires technology, infrastructure and manpower investment which generates business and employment opportunities in the target country, which is why it is motivated.

Read More