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1. High fuel economy and specific power output2. Good drivability3. Extremely low pollution levels4. Easy maintenance5. Adaptation to operating and atmospheric conditions There are two types of electronic injection system 1. Single point fuel injection or throttle body injection or TBI system 2. Multipoint fuel injection- MPFI system *

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Single Point Injection [Throttle Body Injection] TBIIn this system, a simple injector injects fuel just upstream of the throttle valve, serving all cylinders*

*The system is very simple and cheaper But it creates problems in securing equal distribution of fuel to all cylinders incase of multi cylinder enginesFuel particles have a tendency to deposit themselves on the walls of the manifold during cold starting conditions.

*The system is very simple and cheaper

Multipoint port injection - MPFIIn this system, the injectors are located immediately before the inlet valve of each cylinder.Generally one injector for every cylinder.*

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The relative high temperature inlet valve head helps in vaporization of fuel particles The fuel has neither the opportunity to deposit on the walls of manifold, when cold, nor the chances of non-uniform distribution in multi-cylinder engines. The main disadvantage of this system isInjectors have to be accommodated in the cylinder head and they have to withstand the high temperatures. Advantages of port fuel injection: - Increased power and torque due to improved volumetric efficiency (absence of carburetor) More uniform fuel distribution,More rapid engine response to changes in throttle position, Precise control of equivalence ratio during cold starting and engine warm-up.

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Spark plugs

A terminal post on top of the centre electrode is the connecting point for the spark plug cable.

Current flows through the centre of the plug and arcs across the air gap between the tip of the centre electrode to the ground electrode.

The centre electrode is surrounded by the ceramic insulator.

The steel spark plug shell containing the ground electrode is crimped over the insulation.

Spark Plug Design Factors

Size 14 mm or 18 mm

ReachWhere the spark is placed in the cylinder

Heat rangeHeat dissipation rate

Electrode materialCopper and platinum most common

Ignition cables (spark plug cables)

Ignition cables, make up the secondary wiring and carry the high voltage from the distributor or the multiple coils to the spark plugs.

The cables contain carbon fibre cores that act as resistors in the secondary circuit.

They reduce interference, increase firing voltages, and reduce spark plug wear by decreasing current.

Spark plug cable construction

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