ELECTRONIC FUEL INJECTION (EFI)

Electronic Fuel Injection works on the some very basic principle. This system can be divided into three basic sub-system. These are the fuel delivery system, air induction system and the electronic control system.

The Fuel Delivery System:

• The fuel delivery system consist of the fuel tank, fuel pump, fuel injector, fuel delivery pipe (fuel rail), fuel injector, fuel pressure regulator and fuel return pipe.
• Fuel is delivered from the tank to the injector by means of an electric fuel pump. The pump is typically located in or near the fuel tank. Contaminants are filtered out by a high capacity in line fuel filter.
• Fuel is maintained at a constant pressure by means of a fuel pressure regulator. any fuel which is not delivered to the intake manifold by the injector is returned to the tank through a fuel return pipe.

 Air Induction System:

• The air induction system consists of the air cleaner, air flow meter, throttle valve, air, intake chamber, intake manifold runner, and intake valve.
• When the throttle valve is opened, air flows through the air cleaner, through the air flow meter, past the throttle valve and through a well tuned intake manifold runner to the intake valve.
• Air delivered to the engine is a function of driver demand. as the throttle valve is opened further, more air is allowed to enter the engine cylinders.

 Electronic Control System:

• The electronic control system consists of various engine sensors, electronic control unit (ECU), fuel injector assemblies and related wiring.
• The ECU determines precisely how much fuel need to delivered by the injector by monitoring the engine sensors.
• The ECU turn the injectors on for a precise amount of time, referred to as injection pulse width or injection duration. To deliver the proper air/fuel ratio to the engine.

Petrol Engine (Internal Combustion)

A petrol engine (known as a gasoline engine in North Amerika) is an internal combustion engine with spark-ignition, designed to run on petrol (gasoline) and similar volatile fuels.
It differs from a diesel engine in the method of mixing the fuel and air, and in the fact that it uses spark plugs to initiate the combustion process. In a diesel engine, only air is compressed (and therefore heated), and the fuel is injected into the now very hot air at the end of the compression stroke, and self-ignites. In a petrol engine, the fuel and air are usually pre-mixed before compression (although some modern petrol engines now use cylinder-direct petrol injection).
The pre-mixing was formerly done in a carburator, but now (except in the smallest engines) it is done by electronically controlled fuel injection. Petrol engines run at higher speeds than Diesels partially due to their lighter pistons, conrods & crankshaft (as a result of lower compression ratios) & due to petrol burning faster than diesel. However the lower compression ratios of a petrol engine gives a lower efficiency than a diesel engine.


Petrol engines may run on the four-stroke cycle or the two-stroke cycle

Two Stroke:


1. Intake
2. Compression
3. Power
4. Exhaust

Four Stroke:

Spark Plug

A spark plug is an electrical device that fits into the cylinder head of some internal combustion engine and ignites compressed fuels as such aerosol, gasoline, ethanol and liquefied petroleum gas by means of an electric spark.


Spark plugs have an insulated central electrode which is connected by a heavily insulated wire to an ignition coil or magneto circuit on the outside, forming, with a grounded terminal on the base of the plug, a spark gap inside the cylinder. Picture below shows part of spark plug:-

Diagram 1: Single-ground spark plug

How Do You Adjust Spark Plug Gap?

1. Check the owner's manual for your car (or any appliance with spark plugs) to find out the recommended gap setting.
2. Use a gap tool to check the gap of the spark plug. Slip the tool between the ground electrode and center electrode. The gap tool should fit snugly at the recommended gap width indicated on the tool
3. Push the tool between the electrodes a few times to ensure proper gap. If the gap is too wide, push the ground electrode firmly against a flat surface to narrow the gap and then check again with the gap tool.

 

Resource: e-How, NGK SPARK PLUG, 

Step 4

Use a gap tool to check the gap of the spark plug. Slip the tool between the ground electrode and center electrode. The gap tool should fit snugly at the recommended gap width indicated on the tool.

Step 5

Push the tool between the electrodes a few times to ensure proper gap. If the gap is too wide, push the ground electrode firmly against a flat surface to narrow the gap and then check again with the gap tool.

Read more: How to Gap Spark Plugs | eHow.com http://www.ehow.com/how_2213428_gap-spark-plugs.html#ixzz0sieBdL00