Variable Cylinder Management (VCM) System

Variable Cylinder Management (VCM) System

The i-VTEC (intelligent variable valve timing and lift electric control system) adopts a cylinder pause VTEC (variable cylinder system). The cylinder pause VTEC system pauses the intake and exhaust valves on the rear bank under certain conditions such as cruise and fuel cut (see illustration). Since the valves on the rear bank are closed, the frictional losses from valve spring compression and pumping are reduced because no air is compressed in the rear bank. This reduces engine drag.

Operation




During 6 Cylinder Mode (Intake valve side)
The rocker arm oil control valve (VTEC spool valve) switches oil pressure. Oil pressure then enters primary rocker arm A from the oil passage in the intake rocker shaft, and it moves the VTEC switching piston in the rocker arm. This causes the VTEC switching piston to slide into primary rocker arm B, locking primary rocker arms A and B together, Primary rocker arms A and B are then actuated by the secondary rocker arm.




During 6 Cylinder Mode (exhaust valve side)
The rocker arm oil control valve (VTEC spool valve) switches oil pressure. Oil pressure then enters primary rocker arm A from the oil passage in the exhaust rocker shaft, and it moves the VTEC switching piston in the rocker arm. This causes the VTEC switching piston to slide into primary rocker arm B, locking primary rocker arms A and B together. Primary rocker arms A and B are then actuated by the secondary rocker arm.
When the engine is off, the VTEC switching piston is held in the engaged position by the return spring. This allows the rocker arms to operate when oil pressure is low during cranking.




During Cylinder Pause Mode (intake valve side)
The rocker arm oil control valve (VTEC spool valve) switches oil pressure. Oil pressure then enters primary rocker arm B from the oil passage in the intake rocker shaft. This forces the VTEC switching piston into primary rocker arm A against the return spring and disengages the primary rocker arms from the secondary arm to stop valve actuation. The secondary rocker arm uses a lost motion spring to maintain tension.




During Cylinder Pause Mode (exhaust valve side)
The rocker arm oil control valve (VTEC spool valve) switches oil pressure. Oil pressure then enters primary rocker arm B from the oil passage in the exhaust rocker shaft. This forces the VTEC switching piston into primary rocker arm A against the return spring and disengages the primary rocker arms from the secondary arm to stop valve actuation. The secondary rocker arm uses a lost motion spring to maintain tension.