Volvo 819 E - Page 51

Group 28 Ignition systems
Design and function - System descriptions
~: ~- -
2
24
EZ - 117K
EZ-117K
B230FIFT
(740: B 230 F/ FT ; 760: B 230 FT I
The control unit (1 I computes th e op timu m timing based on signals from the various sensors and tran smits ignition
pulses to the power stage ( 2) at exactly the right ins tant . At this point , the power stage interrupts the current in the
primary winding of the ignition coil (3). The high -tension cur rent induced in th e secondary is delivered to the appro-
priate spark plug (5) by the distributor (4).
The
timing is computed by the contro l un it on the basis of the following information :
- The
engine load signal is supplied by the fuel in j ection system (lH · 2.21 control unit (12) wh ich, in turn , is supplied
with load signals by the air mass meter .
- A Hall
generator in the distributor (4) supplies an engine speed and crankshaft pos i tion signaL
- Knock is indicated by the knock sensor (2 4) .
- Closure of the thrott le is in dica ted by the throttle switch ( 19 ).
- Any tendency of the engine to overheat is indicated by a therm os tat (20). In th is event, the con trol unit advances
the
timing by 13" if the throttle is closed . ( Th is applies only to B 230 FT variants.!
49