VANOS
VANOS 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
- Double Vanos
- Vanos Performance
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.
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.
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Double VANOS |
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.
For more more information on operation and reference, feel free to check the link below~ :)
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