VANOS

VANOS (abbr. from German variable Nockenwellensteuerung) is an automobile variable valve timing technology developed by BMW in close collaboration with Continental Teves. VANOS varies the timing of the valves by moving the position of the camshafts in relation to the drive gear. This movement varies from 6 degrees of advanced to 6 degrees of retarded camshaft timing.

Single VANOS

VANOS is a combined hydraulic and mechanical camshaft control device managed by the car's DME engine management system. The VANOS system is based on a discrete adjustment mechanism that can modify the position of the intake camshaft versus the crankshaft. Double-VANOS adds continuous adjustability to the intake and exhaust camshafts.

VANOS operates on the intake camshaft in accordance with engine speed and accelerator pedal position. At the lower end of the engine-speed scale, the intake valves are opened later, which improves idling quality and smoothness. At moderate engine speeds, the intake valves open much earlier, which boosts torque and permits exhaust gas re-circulation inside the combustion chambers, reducing fuel consumption and exhaust emissions. Finally, at high engine speeds, intake valve opening is once again delayed, so that full power can be developed. VANOS significantly enhances emission management, increases output and torque, and offers better idling quality and fuel economy.

VANOS was first introduced in 1992 on the BMW M50 engine used in the 5 Series.

VANOS was earlier available from Alfa Romeo. The 2 liter "Nord" engine, used in all Spiders, most GTV's and various coupes and sedans had VANOS. The early systems(early 1980's) were strictly mechanical (centrifugal), and the later systems were electric activated oil pressure operated systems. This was probably the first VANOS available on a production car.

Double VANOS

The first double VANOS system appeared on the S50B32 engine in 1996. Later, BMW added "double" VANOS to its M52TU series of inline 6-cylinder engines, which changed the mechanism from fixed position operation to continuously variable, and added the same functionality to the exhaust camshaft, on a number of its cars. Double-VANOS (double-variable camshaft control) significantly improves torque and emissions since valve timing on both the intake and exhaust camshafts is adjusted to the power required from the engine as a function of gas pedal position and engine speed. On all BMW engines that use single VANOS, except S50B30, the timing of the intake cam is only changed at two distinct rpm points, while on the double-VANOS system, the timing of the intake and exhaust cams is continuously variable through a range of ~40 crankshaft degrees for the intake, and 25 degrees for the exhaust. The advantage of double-VANOS is that the system controls the flow of hot exhaust gases into the intake manifold individually for all operating conditions. This is referred to as "internal" exhaust gas re-circulation, allowing very fine dosage of the amount of exhaust gas recycled.

VANOS Performance

Single and Double VANOS systems due to age and mileage often experience performance issues as well as complete failure of the BMW OEM Buna-N VANOS piston seals (which are often successfully repaired by the use of aftermarket Viton seals to replace the OEM Buna-N seals). Another common effect is a rattling sound coming from the upper valve train assembly. The original seal material was found to be inferior for the application and tends to break down within 75k - 100k miles. VANOS Seal & Rattle kits are available to address these shortcomings from aftermarket suppliers (but not from BMW -- BMW's solution when VANOS units fail is to remove the entire VANOS unit and replace it with a new one). VANOS repair may require special tools (cooling fan clutch wrenches, etc.) that can be rented or purchased from a variety of vendors.

List of VANOS engines

Note: The engines starting with an "N" also have valvetronic variable intake valve opening.

See also

• Subaru Active Valve Control System
• Variable valve timing
• BMW's Valvetronic Variable valve lift system
• GM Northstar System VVT
• Honda VTEC
• Toyota VVT-i
• 4-stroke power valve system