System Operation

Oil Pump 

The engine lubrication system is of the force-feed type in which oil is supplied under full pressure to the crankshaft, connecting rod bearings, timing chain tensioners, piston oil cooling jets and VCT oil control solenoids. The flow of oil to the valve tappets and valve train is controlled by a restricting orifice located in the cylinder head, front camshaft cap.

The lubrication system is designed to provide optimum oil flow to critical components of the engine through its entire operating range.

The heart of the system is a positive displacement internal vain oil pump.

Generically, this design is known as a gerotor pump, which operates as follows:

• The oil pump is mounted on the front face of the cylinder block.
• The inner rotor is piloted on the crankshaft post and is driven through flats on the crankshaft.
• Maximum system pressure is limited by an integral, internally-vented relief valve which directs the excess oil back to the oil pan.
• Oil pump displacement has been selected to provide adequate volume to make sure of correct oil pressure both at hot idle and maximum speed.
• The relief valve calibration protects the system from excessive pressure during high-viscosity conditions.
• The relief valve is designed to provide adequate connecting rod bearing lubrication under high temperature and high-speed conditions.
• 2-stage operation of the oil pump is controlled by an integral solenoid on the pump that will switch the pump between high and low mode operation.
• The engine PCM sends a 12 volt signal to the oil pump solenoid to switch the pump to low mode. Default is no voltage or high mode operation.
• Both low and high mode maintain required oil pressure to protect and maintain engine function at their specified speeds, engine load (throttle position), and engine temperature.
• Low mode operation is designed to maintain oil pressure between 20 to 30 psi at speeds from 1000 to 3000 rpm with low engine load and engine oil temperatures at normal operating conditions.
• High mode operation is at all other engine operating conditions.

Valve Train 

The valve train uses direct acting mechanical buckets (DAMB). The camshaft lobes are positioned directly above mechanical buckets which are positioned on top of the valves.

Twin Independent Variable Cam Timing (Ti-VCT) 

The twin independent VCT system allows variable control of the valves closing which optimizes combustion at full load providing improved power and low speed torque (broadening the torque curve) which enables variable valve overlap which provides better fuel economy and emissions and provides optimized cold start operation with improved exhaust emissions.