System Operation

Lubrication System 

The engine lubrication system is of the force-feed type in which oil is supplied under full pressure to the crankshaft, connecting rod bearings, camshaft bearing caps and variable camshaft timing (VCT) solenoids. The flow of oil to the valve tappets and valve train is controlled by a restricting orifice located in the cylinder head gasket. Conventional oil pumps account for up to 10% of the mechanical power losses at the nominal speed of an engine, leading to increased fuel consumption. This is caused by the high output of the oil pump, especially at high engine speeds. When a variable oil pump is used, the output can be matched to the required oil flow in a flexible manner, depending on the temperature and the engine speed.

The principle component of the variable oil pump is formed by a vane pump with an adjustable outer ring (vane pump adjusting ring). The vane pump adjusting ring is moved to the left or right depending on the oil pressure.

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 gear oil pump.

Generically, this design is known as a variable oil pump or vane-type pump, which operates as follows:

• The oil pump is driven from the crankshaft.
• At low engine speeds with maximum eccentricity of the vane pump, the maximum volume flow is supplied.
• At high engine speeds, the volume flow increases and with it the oil pressure also. From an oil pressure of approximately 3.25 bar, a valve in the oil pump housing opens (not visible in the illustration), and this causes the oil pressure controlled adjusting ring of the vane pump to be pressed to the left.
• Because of the movement of the adjusting ring, the eccentricity decreases and consequently the delivery volume of the vane pump is reduced. Because of the reduction in the delivery volume, matching to the actual requirement of the internal combustion engine is achieved.
• Advantage: The output can be flexibly matched to the required oil volume flow. Because of this, the power drain at the oil pump is lower, ultimately leading to a reduction in fuel consumption and exhaust emissions.

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 Ti-VCT system allows variable control of the valves 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.