AUTOMOBILE ENGG.

CRDI (Common Rail Direct Injection):-

CRDi stands for Common Rail Direct Injection meaning, direct injection of the fuel into the cylinders of a diesel engine via a single, common line, called the common rail which is connected to all the fuel injectors.

Whereas ordinary diesel direct fuel-injection systems have to build up pressure anew for each and every injection cycle, the new common rail (line) engines maintain constant pressure regardless of the injection sequence.

Advantages & Disadvantages

Advantages:-

CRDi engines are advantageous in many ways. Cars fitted with this new engine technology are believed to deliver 25% more power and torque than the normal direct injection engine. It also offers superior pick up, lower levels of noise and vibration, higher mileage, lower emissions, lower fuel consumption, and improved performance.

In India, diesel is cheaper than petrol and this fact adds to the credibility of the common rail direct injection system.

Disadvantages:-

Like all good things have a negative side, this engine also have few disadvantages. The key disadvantage of the CRDi engine is that it is costly than the conventional engine. The list also includes high degree of engine maintenance and costly spare parts. Also this technology can’t be employed to ordinary engines.


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DRUM BRAKE:-


  
A drum brake is a brake that uses friction caused by a set of shoes or pads that press against a rotating drum-shaped part called a brake drum.


The term drum brake usually means a brake in which shoes press on the inner surface of the drum. When shoes press on the outside of the drum, it is usually called a clasp brake. Where the drum is pinched between two shoes, similar to a conventional disc brake, it is sometimes called a pinch drum brake, though such brakes are relatively rare. A related type called a band brake uses a flexible belt or "band" wrapping around the outside of a drum The modern automobile drum brake was first used in a car made by Maybach in 1900, although the principle was only later patented 1902 by Louis Renault. He used woven asbestos lining for the drum brakes lining, as no alternative dissipated heat like the asbestos lining, though Maybach has used a less sophisticated drum brake. In the first drum brakes, levers and rods or cables operated the shoes mechanically. From the mid-1930s, oil pressure in a small wheel cylinder and pistons (as in the picture) operated the brakes, though some vehicles continued with purely mechanical systems for decades. Some designs have two wheel cylinders.



The shoes in drum brakes wear thinner, and brakes required regular adjustment until the introduction of self-adjusting drum brakes in the 1950s. In the 1960s and 1970s, disc brakes gradually replaced drum brakes on the front wheels of cars. Now practically all cars use disc brakes on the front wheels, and many use disc brakes on all wheels. However, drum brakes are still often used for handbrakes, as it has proven very difficult to design a disc brake suitable for holding a parked car. Moreover, it is very easy to fit a drum handbrake inside a disc brake so that one unit serves as both service brake and handbrake.

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DTSi 4 - VALVE TECHNOLOGY


Pulsar 135 LS is incorporated with World’s First DTSi 4 valve Engine –designed for better performance than an equivalent capacity 2 Valve Engine.



This engine has 2 intake & 2 Exhaust valves compare to 1 intake & 1 Exhaust Valve of a 2 valve engine. These valves are smaller & light weight compared to that of 2 valve engine. 4 Valves (2 Intake & 2 Exhaust valves) are introduced to improve breathing means - intake & Exhaust process of engine.


A typical 2 valve engine has just 1/3 combustion chamber head area covered by the valves, but a 4 valve head increases that to more than 50% area.

Because of this flow area of intake & Exhaust port / passages leading to valves also get increased. This facilitates induction of more quantity of charge (air-fuel mixture) and also evacuation of all burnt gases inside the combustion chamber ensure faster, cleaner & more efficient combustion.

The result is increased engine performance-power, throttle response, pick up of all engine speeds.Moreover the 4 valve engine can be revved up to much higher rpm easily, there by allowing the rider to enjoy light sports bike performance.


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GLOW PLUG :-



Diesel engines, unlike petrol engines which rely on a spark to ignite the air-fuel mixture, function due to the auto-ignition of diesel fuel when subjected to high pressures. Under high pressure, the temperature of the diesel fuel increases to a point where the fuel self-combusts. In cold weather however, this temperature is not always achieved and glow plugs assist by heating the air-fuel mixture to assist in cold starting.
Put simply, glow plugs are small heaters.

So,  basic function of a glow plug is to raise the temperature inside the cylinder, so that sufficient heat is generated to ignite the diesel fuel on starting.

How it works?

A glow plug is an electrical resistor. When electricity passes through it the resistance creates heat causing the glow plug to heat up. A light bulb filament works the same way.The reason glow plugs help start the engine is because diesel engines use heat that is created from compressing air in order to ignite the fuel. Glow plugs help warm a cold part of the engine to aid starting. When the engine is cold the metal in the engine absorbes the heat caused from compression causing the air to not reach the temperature necessary in order to ignite the fuel. If the fuel does not ignite the engine will not run. A warm engine does not assorb as much heat and therefore the engine will start and run just fine. The glow plugs help the engine to start so that it can warm up and supply its own heat. 



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