How Does a Distributor-Based Ignition System Work?

The distributor-based ignition system is a mechanical ignition system where the engine’s moving parts help to get the ignition done. In this article, I will discuss what a Distributor-Based Ignition System?

Distributor-Based Ignition System

Distributor-Based Ignition System

The distributor is used in the automobile system to provide the current to the spark plug, to ignite the fuel and air mixture. The distributor system is used in the SI engine because, in the CI engine, there is no need for the spark plug to ignite the fuel. 
In the earlier days, there was the electromagnetic system, to provide the current to the ignition coil.
In this system, the camshaft is the reason to drive this system. The distributor-type ignition system also relies on the firing order of the engine. Later in this article, I will discuss the firing order.

How Does a Distributor Type Ignition System Work

When the engine rotates it also turns the camshaft with it. The engine crankshaft and the camshaft are connected through a belt or chain. As the camshaft rotates, the lobes of the camshaft rotate the distributor shaft. 
The drive shaft is rotated at half the engine speed in four-stroke engines. When the shaft moves, it opens and closes the breaker points. The breaker cam contains the same number of lobes as the number of cylinders in the engine. 
A rotor is mounted on the breaker cam which is carried by the drive shaft. The rotor connects the central terminal of the cap with each outside terminal in turn, so that high voltage surges from the coil are directed first to one spark plug and then to another, according to the firing order. 

Components of Distributor 

Components of Distributor


The major components of a distributor are – 
  1. Distributor Housing.
  2. Driving Shaft.
  3. Breker Plate.
  4. Governor.
  5. Condensor.
  6. Rotor.
  7. Advance Mechanism.
  8. Cap.


Let’s discuss each of these components- 

1. Distributor Housing

Distributor housing is the outer casing of the Distributor hub. The distributor casing is made of fine aluminum for lightness and hardness. The distributor casing also protects the whole distributor system from outer shock or vibration. 

2. Driving Shaft

The distributor shaft is connected to the engine’s camshaft. when the engine is turned on, the camshaft also rotates. The drive shaft is connected to the engine camshaft mechanically, which is responsible for synchronizing the ignition timing with the engine’s rotation.

3. Breker Plate

The breaker plate is the component where the contact breakers are connected. The breaker plate is responsible for the sparking in the spark plug. The breaker plats help the breaker points to cut off and add on the electric current. 

4. Governor

In a distributor-based ignition system, the governor is the mechanical component. The governor is used in the system to control and regulate the engine speed by adjusting the ignition timing. 

5. Condensor

The condenser is called the capacitor. It is used in the system to reduce arcing and wear at the breaker points within the distributor. The condenser is connected to the distributor parallel to the breaker points. 

6 Rotor

The rotor is a plastic shaft mounted on the top of the distributor cap. The responsibility of the rotor is very high because the rotor is responsible for sending the correct current to the specific spark plug. It ensures the firing order of the engine.

7. Advance Mechanism

The advance mechanism is used in the distributor to precise the timing of the spark. Especially, in the higher engine speed it advances the ignition process to reduce th lag. This process also helps in scavenging the engine.

8. Cap

The cap is called the distributor cap in the system. It protects the internal component of the distributor from dust water and debris. 

Disadvantages of the Distributor Ignition System

The distributor types ignition system has several disadvantages. Nowadays there are electromegantic systems of Ignition available in the automotive sectors. Let’s talk about the disadvantages-
> In a distributor-based ignition system the engine efficiency and power loss happens due to the insufficient timing of ignition. 
> This system needs regular maintenance to replace the condenser and contact breaker points, for any damage or corrosiveness.
> This system has many more mechanical components like a rotor arm, drive shaft, and many other components. These components need to be changed after a certain period of time. 

> In higher RPM, the distributor is not able to send the current to the spark plug, which causes the engine to misfire. 
> The ignition delay is there for the limited supply of electricity from the rotor. 
> The shaft and the other mechanical parts need lubrication, that’s why the sludge formation also happens in the cylinder.
> Distributor ignition systems are considered obsolete in modern automotive engineering. Most new vehicles use electronic ignition systems because they offer better control, reliability, and performance.

Firing Order in Distributor Ignition System

The order or sequence in which the firing takes place in different cylinders in the multi-cylinder engine is called the Firing Order. In a spark ignition engine, the high-tension leads from the distributor are connected to the spark plugs at different cylinders according to the firing order. A proper firing order reduces engine vibrations, maintains engine balancing, and secures an even flow of power. The firing order differs from engine to engine. Probable firing orders, for different engines are as follows- 

3-cylinder engine firing order

> 1-2-3

4-cylinder in-line engine firing order

> 1-3-4-2
> 1-2-4-3

6-cylinder in-line engine firing order

> 1-5-3-6-2-4
> 1-4-2-6-3-5
> 1-3-2-6-4-5
> 1-2-4-6-5-3

8-cylinder in-line engine firing order

> 1-5-3-6-2-4-7-4
> 1-4-7-3-8-5-2-6

8-cylinder V-type engine firing order

> 1-5-4-8-6-3-7-2
> 1-5-4-2-6-3-7-8
> 1-6-2-5-8-3-7-4
> 1-8-4-3-6-5-7-2
> 1-8-7-3-6-5-4-2
Cylinder no.1 is taken from the front of the in-line engines whereas in V-type engines, it is taken from on right side bank. 


I have discussed the Distributor-based ignition system in this article. This system is based on mechanical work, but nowadays the electrical ignition system is there and is controlled by the ECU.
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