A look at the amazing single and double Vanos Control systems.

"BMWs VANOS Explained"

In this article we will endeavor to explain the basics of what VANOS is. VANOS stands for VAriable Nockenwellensteuerung (which translates from German to English to variable camshaft control).

It is a system originally developed by BMW for models produced during and after 1992. There are two types of VANOS, single and double. The first engine to feature VANOS was the M50 (found in a variety of models), double VANOS first appeared in the S50B32 (used in the M3 Evo, Z3M and Z4M) in 1996.

Single VANOS uses a mechanical and hydraulic adjustment to the position of the intake camshaft against the crankshaft.

The position is adjusted according to the engine speed and accelerator pedal position. At low speeds the intake valves are opened later which contributes to the renowned 6 cylinder smoothness and also helps the idle.

Once speeds are increased the intake valves open earlier allowing more torque, less fuel consumption and lower emissions (this is because the exhaust gasses re-circulate inside the combustion chambers).

At high speeds the intake valves once again open later. This enables full power to be achieved.

What exactly is VANOS, what does it do for your engine and how does it work.

Double VANOS works much the same as single VANOS, however whilst the single system uses two fixed points in the RPM range, the double system use a continuous adjustment, again according to speed and the accelerator pedal position.

Double VANOS also extends to the exhaust camshaft as well. Torque is further increased and emissions are further improved as a result.

Whilst VANOS is usually reliable, age related problems can mean repairs are necessary. The most common problem is the rattle that is found in the upper valve train assembly.

camshafts

If the mileage of the engine is around 100k, listen carefully when buying. The only method to prevent failure is to replace the seals with aftermarket items. The other notable problem is the piston seals can fail. This is due to age and mileage. Once again, prevention is better than cure so if the engine is of high mileage then be sure to change the piston seals.

Single VANOS is found in the following engines:
M50
M52
S50
S52
M62TU

Double VANOS is available in the following the engines:
M52TU
M54
N52
S50
S54
N62
S62
S85
N73

Please remember that some variances in the specification appear in the US models.

Written by Matt Ayling (a.k.a. forum member Prince)

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