This document summarizes the main components and functions of a spark plug. It describes the terminal, shell, resistor, insulator, central electrode, and ground electrode. It explains that spark plugs use different materials like nickel copper alloy, platinum, or iridium in the central electrode, and can be classified as hot plugs or cold plugs depending on the length of the insulator tip and intended engine application. Selecting a spark plug with too high or too low of a heat range can cause issues like carbon buildup, miss firing, or engine damage.

1. SPARK PLUG

2. What is a spark plug ?
• It is a device for delivering electric current
from an ignition system to the combustion
chamber.

3. PARTS
• TERMINAL
• SHELL
• RESISTOR
• INSULATOR
• CENTRAL ELECTRODE
• GROUND ELECTRODE

4. • TERMINAL
It is the part on which the high voltage from
the ignition coil is connected.
• RESISTOR
Used to eliminate the electrical or radio
interference.

5. SHELL
• Shell is designed with a thread that screws
into the combustion chamber.
• Acts as an earth point.

6. INSULATOR
• Function is to provide mechanical support and
electrical insulation for central electrode.
RIBS -
• It is designed to lengthen the distance
between upper insulated terminal and earth
shell as much as possible.

7. CENTRAL ELECTRODE
• It is connected to the terminal .
TYPES
• Nickel copper alloy
• Platinum
• iridium

8. Nickel copper alloy
• Allows the plug to heat up and also dissipate
heat quickly.
• but it subject to corrosive degradation.
• Diameter of central electrode - 2.5mm.
• service life - 20000 miles

9. PLATINUM
• Excellent corrosion resistance.
• Does not conduct electricity as Nickel copper
alloy.
• Diameter of central electrode – 1.1mm
• Service life – 100000 miles

10. • IRIDIUM
• Good conductor and six times harder than
platinum.
• Diameter of central electrode – 0.5mm
• Service life – 60000 miles

11. GROUND ELECTRODE
• Is welded on to shell.
• Made up of same material
of shell or coated with platinum.
• The shell may have one or more
ground electrode (current can
choose a least resistant path).
• Some have grove.

12. PRINCIPLE OF GROVE
• It forces the spark to occur at the outer edge
of central electrode.
• Easier to ignite the mixture
• The voltage required to produce spark is
reduced.

13. TYPES OF SPARK PLUG
• HOT PLUG
• COLD PLUG
• Main difference is length of electrode
insulator tip.
• Longer insulator tip makes the plug hotter

14. HOT PLUG
• Has the ability to retain heat at the plug tip.
• Used in lower compression engine. This
means the spark plug will heat up easily and
reach its optimal operating temperature.

15. COLD PLUG
• Has very short heat path so any retained heat
will dissipate much faster.
• Used in high performance engine to resist the
heat produced in the combustion chamber.

16. • What happens when the spark plug selected
for an engine is -
too cold ?
heat range is too high ?

17. • If the spark plug is too cold carbon deposit will
start to develop between central electrode
and shell it makes a ground path for the
current to flow.
• If spark plug heat range is too high then
abnormal pre ignition may occur.
• Leads to - miss firing
melting of spark plug electrode
piston damage…

18. THANK YOU