Intake Rocker Arm Control System Operation: Notes

Fig 1: View Of Intake Rocker Arm Control System

Courtesy of GENERAL MOTORS CORP.

The intake rocker arm control system is designed to change valve timing and lift, depending on engine speed, vehicle speed, engine load, and other sensor inputs, by controlling intake valve rocker arm actuation. The intake rocker arm control system achieves low-end torque and low fuel consumption when operating in the low engine speed range, while maintaining high power output when operating in the high engine speed range. The engine has a normal 4 valve per cylinder arrangement. At low engine speed, the primary (4) and secondary (2) intake valve rocker arms operate at normal lift. At high engine speed, the primary (4) and secondary (2) intake rocker arms are mechanically connected to the mid intake rocker arm (3) to allow high valve lift. Synchronizing pistons (1) connect and disconnect the 3 intake rocker arms. Hydraulic pressure against a timing piston moves the synchronizing piston outward. A stopper piston and return spring move the synchronizing piston back or inward when hydraulic pressure is reduced.

The system consists of the following components:

• A spool valve assembly with solenoid
• An oil pressure switch
• Valve lash adjusters-lost motion assemblies
• An intake rocker arm assembly with moving-internal pistons