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Lotus Service Notes Section EMN
Page 17
EMN.14 - VVC MECHANISM CONTROL SOLENOIDS
The inlet cam period is determined by a hydraulic control unit (HCU) mounted on the right hand front of
the cylinder head. The HCU uses two solenoids to operate a spool valve and control a piston and rack
mechanism, which outputs from the HCU via a control shaft to the two VVC mechanisms. The ECM energises
one solenoid valve at a time to drive the VVC mechanism either towards maximum, or towards minimum inlet
cam period. The desired period is calculated by the ECM primarily using engine speed and MAP signals, with
the current period measured by the cam position sensor.
To replace the solenoids:
- Unplug the harness connectors;
- Release the adjacent breather pipes and harnesses to provide access to the sleeve nut;
- Remove the nut and slide the two solenoids off the spool valve shaft, taking care not to misplace the 'O'
rings and spacer.
When refitting, lubricate all 'O' rings and spool valve shaft with engine oil, and note that although the two
solenoids are identical, the correct harness plug must be connected to each; black to RH solenoid, blue to LH
solenoid. Assemble onto the spool valve shaft in the following order:
- 'O' ring;
- One solenoid with lettering on end surface facing away from HCU;
- Spacer with 'O' ring fitted;
- Second solenoid with lettering on end surface facing away from HCU;
- End nut with 'O' ring fitted;
- Position solenoids to allow connector plugs to be fitted before tightening nut to 12 Nm.
Hydraulic
control unit (HCU)
Spool valve shaft
'O' ring
Connect black harness
plug to solenoid valve
End nut
'O' ring on
spacer washer
Connect blue em219b
'O' ring harness plug
to solenoid valve
End face lettering