oil change BMW X5 1999 E53 M54 Engine Workshop Manual

32
M54engMS43/ST036/6/2000
MS 43 CARRY OVER FUNCTIONS
OUTPUT FUNCTIONS -VANOS CONTROL
With the double VANOS system, the valve timing is changed on both the intake and the
exhaust camshafts.
Double VANOS provides the following benefits:
• Torque increase in the low to mid (1500 - 2000 RPM) range without power loss in the
upper RPM range.
• Less incomplete combustion when idling due to less camshaft overlap (also improves
idle speed characteristics).
• Internal exhaust gas recirculation (EGR) in the part load range (reduces NOx and post-
combustion of residual gasses in the exhaust)
• Rapid catalyst warm up and lower “raw” emissions after cold start.
• Reduction in fuel consumption
Double VANOS consists of the following parts:
• Intake and exhaust camshafts with helical gear insert
• Sprockets with adjustable gears
• VANOS actuators for each camshaft
• 2 three-way solenoid switching valves
• 2 impulse wheels for detecting camshaft position
• 2 camshaft position sensors (Hall effect)
The “initial” timing is set by gear positioning (refer to the Repair Instructions for details) and
the chain tensioner. As with the previous VANOS, the hydraulically controlled actuators
move the helical geared cups to regulate camshaft timing. The angled teeth of the helical
gears cause the pushing
movement of the helical cup to be converted into a rotational
movement. This rotational movement is added to the turning of the camshafts and cause
the camshafts to “advance” or “retard”. The adjustment rate is dependent oil temperature,
oil pressure, and engine RPM.