When the engine is running, the ignition coil receives a signal from the engine control unit to fire at the correct time. The coil then rapidly builds up a magnetic field within the primary winding when the signal is received, and when the signal is cut off, the magnetic field collapses rapidly, inducing a high voltage in the secondary winding. This high voltage is then sent to the spark plug, where it jumps the electrode gap, igniting the air-fuel mixture in the combustion chamber.
Metal O.D. wall
(with a reinforcing inner metal case)
Leather is probably the oldest of the lip materials still in common use, but the move towards mass production methods has seen a massive increase in the development of synthetic rubbers which lend themselves to accurate and repeatable injection and compression moulding. Nitrile (NBR) is still by far the most common elastomer for “normal” use, whilst Viton® (FKM/FPM) is rapidly replacing Polyacrylate (ACM) and Silicone (VMQ) for high-temperature applications. Viton® also has high resistance to abrasion and chemical attack making it a preferred elastomer. Recent developments in the use of PTFE for Rotary shaft seals has caused widespread interest particularly for high-speed shaft rotation or poor lubrication applications.