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Wednesday, 20 September 2017

How Car Ignition System Works

Hi friends ….Its BISWANATH BAI, here with a new topic on HOW IGNITION SYSTEM WORKS. An ignition system of INTERNAL COMBUSTION ENGINE is totally different from ROCKET ENGINE or CYROGENIC ENGINE. If you don’t know how rocket engine works then must read HOW ROCKET ENGINE WORKS.

Let's start the topic....

By Frédéric MICHEL [GFDL (http://www.gnu.org/copyleft/fdl.html) or
 CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
 You must have known about spark plug that ignites the fuel, but in an ignition system, there is a hell lot of thing to know. In tradition petrol powered spark ignition internal combustion engine, the fuel is ignited just before the piston reaches the TDC part. In diesel engine fuel is ignited due to high compression & temperature, but in a petrol engine, a Sparkplug is used to ignite the fuel. Simply an ignition system starts from turning on the key and ends at after igniting the fuel at spark plug fuel. In-between this two parts a lot of things happen. The main thing in ignition system is timing. The system also develops a low tension current (LT current) to a High tension (HT) current.So let’s know how this thing is done????

Well in a traditional ignition system there are 7 basic parts i.e.
1.    Battery
2.    Ignition Coil
3.    Contact breaker
4.    Condenser
5.    Distributor
6.    Spark Plug etc.

CONSTRUCTION

The construction starts from the Battery. The +ve terminal is connected to the key locker and –ve terminal is grounded. To the key, the Ignition coil is connected. The ignition coil contains 2 types of coil i.e. Primary coil which
is connected to the Contact breaker & Condenser. As you can see in the image the ignition coil has 3 ports one is for input & another is for output. One output goes to the Contact breaker from primary coil & Condenser, and other output goes to the Distributor from secondary coil. The next part is the Contact breaker & Condenser. The output terminal of both the parts is grounded. A contact breaker consists of a cam which is driven by a camshaft or countershaft & a CB switch which ups & down with the movement of the cam.



Now the distributor which is connected to the secondary winding consists of one rotor, No. of points according to the no. of engine Cylinder. In the image, it has 4 Cylinder so it has 4 points. Those points are connected to the spark plug.




Next is the spark plug, the outer part of the spark plug is grounded & have an a-Grounded electrode on the tip and b-central electrode goes through the center of the body Insulated by a ceramic layer. The size o the ceramic layer depends upon the type of spark plug i.e. hot & cold spark plug. Hot plug have small size ceramic layer and Cold plug have a bigger ceramic layer. Some gap of usually 0.025mm to 0.035mm is maintained between the central & grounded electrode to cause a spark. The spark plug is installed on the overhead part or on the top part of the engine cylinder. That’s all that was the complete construction of engine cylinder. Now let’s know how it works????

How Car Ignition System Works??
(For better understanding look at the image)

The working phenomena of Ignition System are very simple. When we turn on the key, LT current of the battery is passed through the primary winding of ignition coil & reaches Contact Breaker. The phenomena of contact breaker are little tricky but it has a lot of work to do. There is a contact of CB which connects to the grounded to floe the LT current. When the cam lobe pushes the switch it moves upward disconnect the point. The contact breaker acts as a switch for distributer. The cam & cam lobe is installed in such a way that it disconnects the circuit right the time of spark opposing the back EMF to damage the CB contact point and reach ignition coil.
By Frédéric MICHEL [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Now when the CB contact point breaks, the secondary coil develops an HT (high tension) current & supply it to the Distributor where a rotor rotates 360’ at a speed depending upon the engine load. This rotor supplies HT current to the central electrode of the spark plug at the perfect time set by the manufacturer. There is a chance that an arc of current may occur with between the rotor end & points due to HT current. This is controlled by the distributor.

As we know there is a gap between central & grounded electrode.When HT current flows to the gas, it ionized the air causing the current to flow & creates a spark which ignites the fuel. This where the back EMF is developed.

The timing of Ignition largely depends on the Distributor. In new developments, they use an ECU & some sensor to eliminate Distributor for more accuracy and efficiency. The sensor senses the piston position & inform the ECU which then governs the ignition timing according to the data.This gives more accuracy & Pre-sized controlled over Ignition Timing.

Here is something to know about IGNITION SYSTEM….

  1. If the speed of engine increases, the faster the engine goes, the spark has to occur earlier.
  2. RETEARING THE SPARK- Is happens when the spark timing is move to closer to top of the compression stroke.This is done to reduce maximum cylinder pressure & temperature to minimise emission. This also eliminates the KNOCKING.  
I hope you understand How ignition system works, now....If u have any problem or question then please comment below.... I will be happy to help you.


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