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Group 28 Design and Function
Injector Operational Phases
The operational phase of the number 1 cylinder is given
in the following example. Fuel is injected at 7
before top
dead center (BTDC) (the injection angle may vary be-
tween 18
BTDC and 6 after top dead center).
The cam sensor reacts to the extra tooth on the cam
sensor wheel. This informs the control unit that the next
tooth in turn (tooth 1) indicates the number 1 cylinder.
T2007100
Locating number 1 cylinder
A top dead center (TDC)
The cam sensor wheel detects tooth 1 and the flywheel
sensor reaches a flat area on the flywheel at the same
time.
At this point, the piston is on its way upward in the cylin-
der and no fuel is injected into the cylinder.
T2007101
Engine speed calculated
A top dead center (TDC)
The sensor detects the first notch after a flat area on the
flywheel. Using the engine speed calculation, the EECU
can determine:
•
When to begin injecting fuel into the number 1 cylin-
der. This gives selected injection angle (7
BTDC in
the example).
•
When to stop injecting fuel into the number 1 cylin-
der. This gives the selected fuel amount.
T2007102
Calculating injection angle
A TDC
B 7 BTDC (injection begins)
C ATDC (injection stops)
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