VANOS is a significant technological development in providing improved performance while maintaining mild driving characteristics. VANOS is driven using engine oil pressure as hydraulics controlled oscillating signal from the ECU to a pair of electric solenoids.
This is maintained by modulating the solenoid (switching the solenoid on and off really fast). It can (apparently) span a range of frequencies from approx. 100 to 220 Hz. thus moving the vanos piston infinitely from full advance to full retard.
This complex map is what the ECU used to determine the propper angle for each camshaft to provide the optimum performance and economy given the load, rpm, pedal position, temperature etc. Simple but very effective.
Due to the fact that VANOS uses engine oil to operate and it is really a sensitive hydraulic system is it suggested that changing the oil and filter every 5,000 miles with something on the high viscus side. I use 20w50 in summer down here in the south and 10W40 in winter.
As I said in the engine section, at 340,000 miles the factory crosshatch hone marks were still on the cylinder walls and they were round and straight as from the factory. Do not get sucked into the hype around oils. The 15,000 mile oils change strategy professed by BMW is designed to wear your engine out prematurely so you’l buy a new one.
