3 Series E36 M3 (S50) COUPE
11 36 000
Description of VANOS function (variable camshaft spread) (S50 B30)
General
VANOS has the task of adjusting the spread of the intake camshaft in a variable manner from advance to retard and
vice versa.
Opening and closing times for intake camshaft are adjusted between advance and retard in a parallel fashion.
The VANOS system is controlled by a dedicated VANOS control unit which is connected by CAN (Controller Area
Network) to DME (Digital Engine Electronics) M3.3.
In contrast to M50 VANOS, this adjustment is an infinitely variable process.
Governed maximum speed of 250 km/h is also controlled by VANOS adjustment unit.
Development of this system achieved following objectives:
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Increase in torque in central speed range, increased performance in higher speed range by extended timing
intervals
-
Less unburnt residual gases at idle speed achieved with smaller spread, thereby improving idle characteristics.
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Catalytic converter reaches operating temperature faster after cold starts
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Reduction of fuel consumption
Operation
VANOS housing contains VANOS compressed-oil pump, two solenoid valves and adjustment cylinder.
The VANOS control unit determines the optimum position for the intake camshaft from the throttle valve position signal
and the engine speed. Continuous sensing of notched gears by sensors checks the relative angle setting between the
intake camshaft (adjustable shaft) and exhaust camshaft (reference shaft), compares this with the specified nominal
value and, when required, energizes the solenoid valves.
Adjustment of intake camshaft is performed by a control piston which is connected to an adjustable splined shaft.
The camshaft and sprocket wheel with integral actuator transmission are connected by splined shaft.
When control piston is displaced, splined shaft in actuator transmission rotates camshaft relative to sprocket wheel.
Oil pressure required for adjustment is generated by VANOS compressed-oil pump (radial piston pump).
Function of VANOS hydraulic system
Engine oil pump carries oil to VANOS compressed-oil pump. This pump is driven by exhaust camshaft and develops
continuous pressure of 100 bar
To develop pressure immediately when a solenoid valve opens, hydraulic system is equipped with an oil accumulator.
If a calculation in VANOS control unit calls for a retard adjustment to intake camshaft, solenoid valve 1 remains closed
and solenoid valve 2 opens.
Note:
Valves are closed when de-energized.
This means that oil pressure is only developed on reverse side of piston. Control piston in adjustment cylinder moves in
direction of tavel and splined shaft rotates camshaft in its retard direction.
When engine is started, initially both solenoid valves are closed. Immediately after start, VANOS control unit decides
whether camshaft adjustment is actually necessary.
At idle speed, intake camshaft points towards its retard setting.
RA Description of VANOS function (variable camshaft spread) (S50 B30)
BMW AG - TIS
09.02.2013 20:59
Issue status (12/2007) Valid only until next DVD is issued
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