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ControI unit

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Fig. 36 Błock diagram of the control unit

tends the valve control pulses by the amount t_s of the voltage-dependent re-sponse delay of the injection valves.

The total duration of the injection pulses t, consists of the sum of

/p "h /m "h ts.

Injection pulses

The injection pulses generated by the multiplying stage are amplified in a foliowi ng finał stage. The injection valves are controlled with these amplified pulses.

Ali the injection valves in the engine open and close at the same time. With each valve a series resistor is wired into the Circuit as a current limiter.

Ignition sequence of the    _l_

cylinders and opening times of _;    ;

the injection valves

0= 360= 720= KW
		1	i i
	I		i	i
		zr			i

Ignition delivers trigger pulses

W-

H-

w

K

W

L

Pulse shaper generates rectangular pulses from tHese trigger pulses

Frequency divider halves the pulse sequence in order to provide triggering pulses for the injection valves

Diyision conirol multivibrator generates the basie injection time r_D

Multiplying stage processes the correction quantities and aaaptation quantities correction time r₅ voltage correction time

- U

Finał stage delivers amplified voltage pulses r for the injection valves

r, = r₀ + /„ +1.

The finał stage of the L-Jetronic sup-plies 3 or 4 valves simultaneously with current. Control units for 6 and 8-cyl. engines have two finał stages with 3 and 4 injection valves respectively. Both finał stages operate in unison. The injection cycle of the L-Jetronic is selected so that for each revolution of the camshaft half the amount of fuel re-ąuired by each working cylinder is in-jected twice.

In addition to controlling the injection valves through series resistors some control units have a regulated finał stage. In these control units the injection valves are operated without series resistors. Control of the injection valves takes place then as follows: as soon as the valve armatures have operated at the beginning of the impulse, the valve current is regulated for the rest of the impulse duration to a consi-derably reduced current, the holding current. Since these valves are switched on at the start of the impulse with a very high current, short re-sponse times are the result. By means of the reduction in current strength af-ter switching on, the finał stage is not subjected to such heavy loading. In this way up to 12 valves can be switched with one finał stage.

Fig. 37 Generation of the injection pulses in the control unit for a 4-cyl. engine.

^QKW = ^Ccrankshaft