Ignition Coils - Fiat Bravo Service Manual

Engine
Fuel system
10.
28
Bravo-Brava
IGNITION C O I L S
The ignition circuit is the inductive discharge,
static advance type where the high tension is
provided from two t w i n outlet coils fitted at
the side of the cylinder head.
The coils used are the closed magnetic circuit
type w i t h the windings in a plastic container
immersed in epoxide resin. Each coil is c o n -
nected to the t w o spark plugs by means of
high tension leads w i t h dielectric properties.
In this type of coil the current in the sec-
ondary w i n d i n g (discharge current) always
has the same polarity: therefore one end of
the circuit has a positive potential and the
other a negative potential.
This implies that the discharge current in the
secondary winding always flows in the same
direction and therefore the sparks for the t w o
cylinders connected to the coil strike I n the
opposite way:
- in the spark plug w i t h the positive centre
electrode the spark strikes from the earth
electrode towards the centre one;
- in the spark plug w i t h the negative centre
electrode the spark strikes from the centre
electrode towards the earth one.
As a result the wear of the electrodes be-
tween the t w o spark plugs in question is dif-
ferent.
Since the intensity of the spark depends on
the resistance between the electrodes (di-
electric), whilst the spark in the cylinder in
the cross-over stage is weak (lost spark), at
alsmot atmospheric pressure in the cylinder
at the end of the compression stroke, the
spark is intense (working spark) by virtue of
the high pressure in the chamber.
Wiring connector
njp*
16v
98 range
Print no. 506.670/16