System Components: VANOS: Notes

Performance, torque, idle characteristics and exhaust emissions reduction are improved by variable camshaft timing (VANOS). The S62 engine uses a double VANOS system for valve timing on both the intake and exhaust camshafts.

Fig 1: Front View Of Engine Equipped With VANOS System

Courtesy of BMW OF NORTH AMERICA, INC.

The S62 uses a high pressure (100 Bar) control system that ensures quick and reliable adjustments of the camshafts to meet the high performance requirements of the M Engines. The VANOS units are mounted directly on the front of the cylinder heads.

Each VANOS unit contains:

High pressure radial oil pump (driven by the intake Camshaft)
Two inlet solenoids
Two outlet solenoids
Two adjustment pistons
Two hydraulically actuated adjustment shafts

Fig 2: Identifying VANOS Unit Components
Courtesy of BMW OF NORTH AMERICA, INC.

Two solenoids are required for each adjusting piston circuit, one for advancing and one for retarding the camshaft timing. The solenoids are controlled by the ECM.

The adjustment shafts contain two sets of splines that engage with:

Camshaft Sleeves (Straight Splines)
Chain Driven Sprocket (Helical Splines)

The adjustment shafts have a total stroke of 25 mm.

Fig 3: Identifying Adjustment Shafts

Courtesy of BMW OF NORTH AMERICA, INC.

The camshaft sleeves are bolted to the end of the camshafts and engage with the straight spline of the adjustment shaft shown above.

Fig 4: Identifying Adjustment Shafts

Courtesy of BMW OF NORTH AMERICA, INC.

The chain driven sprocket and spacer sleeve assembly is shown to the right (one assembly per camshaft). The sprocket engages with the helical splines of the adjustment shaft shown above.

The intake camshaft sprocket assembly has two drive "lugs" that must be aligned with the radial piston oil pump during installation.

Fig 5: Identifying Chain Driven Sprocket And Spacer Sleeve

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 6: "M" VANOS Operation Diagram

Courtesy of BMW OF NORTH AMERICA, INC.

VANOS mechanical operation is dependent on oil pressure applied to position the control pistons. The double VANOS camshafts are infinitely adjustable within the mechanical travel limits of the drive gears.

When oil pressure is applied to the control piston, the piston moves causing the splined adjustment shaft to move. The straight splines slide within the camshaft sleeve. The helical splines rotate the camshaft drive sprocket changing the position in relation to the camshaft position which advances/retards the camshaft timing.

The total adjustment range of the camshafts is 60° (as referenced to the crankshaft).

The "default" mechanical stop position without VANOS influence is:

VANOS INFLUENCE

Intake Camshaft = Retarded

Exhaust Camshaft = Advance

Oil is supplied from the main gallery through the front of cylinder head (arrow) to the inlet pressure reducing valve.