Bi-VANOS
BI-VANOS (Variable Camshaft Adjustment)
The N62 features compact infinitely variable vane-type VANOS for the intake and exhaust camshafts. The VANOS unit is easy to remove and install. The VANOS unit is designed as an integral component of the chain drive and is secured to the respective camshaft with a central bolt. The camshaft adjustment rate is 60° (as compared with the crankshaft).
The VANOS unit gear teeth are visibly different to match the new toothed chain. The VANOS unit for the cylinders 1-4 exhaust shaft has mounting provisions for the vacuum pump drive. A spring plate is fitted between the VANOS unit and the vacuum pump drive to reduce wear (3). The VANOS units are labeled "In/Out" for intake and exhaust installation positions.
The VANOS units are supplied with oil via ports in the camshafts. The oil ports are located on the left and right of the thrust bearing. Depending on the individual VANOS adjustment direction, the VANOS is supplied with oil via either the rear oil ports (1 & 2) or the front oil ports (3 & 4). The oil moves through the camshaft to the VANOS units.
Camshaft Sensors
The cam shaft sensors (Hall effect) are mounted through the cylinder head cover. There are two sensors per cylinder head to monitor the intake and exhaust camshaft positions.
The sensors monitor the impulse wheels attached to the ends of the camshafts.
Solenoid Valves
The VANOS solenoid valves are mounted through the upper timing case front cover. There are two solenoids per cylinder head to control the oil flow to the camshaft ports for the intake and exhaust VANOS units.
The 4/3 way proportional solenoid valve is activated by the ECM to direct oil flow. The solenoid valve is sealed to the front cover by a radial seal and secured by a retaining plate.
VANOS Sectional Views
Mechanical Layout:
The figures above show a sectional view of one VANOS unit. The VANOS unit is secured by a central bolt through the hub (7) to the camshaft. The timing chain connects the crankshaft with the housing of the unit.
There is a recess in the hub in which the locking pin (6) engages without oil pressure (sprung). When the solenoid valve is activated to supply oil pressure to the VANOS unit, the locking pin is compressed and releases the VANOS for adjustment.
The internal blades (9) are spring loaded (10) to provide a seal between the oil pressure chambers (11 and 12). The torsion spring (3) acts against the camshaft torque.
Hydraulic Actuation:
When oil pressure is applied to chamber A, the blades are forced away from the VANOS housing (counterclockwise). The blades are keyed into the hub which results in the hub position being rotated in relation to the housing (with sprocket). The hub is secured to the camshaft which changes the camshaft to sprocket relationship (timing).
The example below shows the adjustment procedure together with the pressure progression based on the VANOS unit for the exhaust camshafts.
During this adjustment chamber B is open (through the solenoid) to allow the oil to drain back through the cylinder head (internal reservoir).
When the solenoid valve switches over, oil pressure is applied to chamber B. This forces the blades (and hub) in a clockwise direction back to the initial position, again changing the camshaft timing.
The example below shows the reset procedure together with the pressure progression based on the VANOS unit for the exhaust camshafts.
During this adjustment chamber A is open (through the solenoid) to allow the oil to drain back through the cylinder head (internal reservoir).
The chart below shows the VANOS unit camshaft adjustment possibilities. The valve lift adjustment has also been incorporated.
The special feature of Valvetronic is that the air mass drawn in the cylinders can be easily determined by the valve lift and closing time. The air mass can then be limited, thus the term "load control".
With the help of VANOS, the valve closing point can be easily selected within a defined range. With valve lift control, the opening duration and cross section of the valve opening can also be easily selected within a defined range.