Fuel and ignition system 9112 · 1537 Actuation of solenoid hydraulic

Fuel and ignition system 9112 1537 Actuation of solenoid hydraulic valve to adjust valve timing The control unit determines the current position of the intake camshafts in relation to crankshaft (actual angle) using the en- gine speed signal and Hall sensor signal. The position control in the control unit re- ceives the desired angle via the pr o- grammed map values (engine speed, load, engine temperature). If the desired angle and actual angle differ, the control ele c- tronics in the control unit actuates the so- lenoid hydraulic valve to move the control element for inlet camshaft in the desired 2_16_02 direction. Actuation of the valve takes place 1 – Solenoid hydraulic valve (for variablevia a pulse-width-modulated square-wave camshaft timing) valve timingsignal. The voltage is switched between 0 2 – Solenoid hydraulic valve (for valvevolts and 12 volts in 4ms cycles (250 Hz), stroke)while the proportion of switch-on and 3 – Ignition coilswitch-off time is changed. A control cur- 4 – Hall sensorrent adjusts itself according to this propor- 5 – Injection valvetion, which sets the piston position in the solenoid hydraulic valve and thereby r e- leases the different oil lines, facilitating an 2839 Hall sensor and camshaft rotor adjustment range of 0 °kW up to approx. 40 °kW. A modified rotor is fitted to the intake cam- shafts of both cylinder banks. Due to the rotor position, the Hall sensor determines 1555 Valve stroke control on bucket the current position of the intake camshaft tappets of intake camshafts 4 times per camshaft revolution and relays this value to the control unit. This deter-The map of the valve stroke control is mines precisely the position of both intakeadapted to the engine-specific require- camshafts.ments. The valve stroke control facilitates switch- ing of the valve stroke of the intake ca m- shaft from 3.6 mm to 11.0 mm. 2873 Engine speed sensor The engine speed sensor on the crankshaft detects the engine speed and current posi- tion of the crankshaft via 60 – 2 teeth and relays the information to the ME 7.8 control unit. 2_09_02 1 – Hall sensor2 – Camshaft rotor 2 - 8 Service Information 2002