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Message: <blockquote data-quote="YYC" data-source="post: 1064119509" data-attributes="member: 59459">What I know is VANOS mechanism is very different from VTEC's, but both utilise the hydraulic pressure to operate the valve timing mechanisms. BMW doesn't employ cam profiling for its VANOS/Valvetronic system (BMW sifoo please confirm). Here is a very good explanation to VANOS operation.The crankshaft and camshaft(s) are connected via a timing belt/chain(s) which synchronizes the timing of the opening/closing of the intake and exhaust valves with the piston cycle/position. E39’s have double overhead camshafts, meaning separate intake and exhaust camshafts found at the top of the engine (head). BMW implements a time shift scheme for variable valve timing. That is, the relative rotational position of the camshaft(s) to the crankshaft is modified (shifted). This is done dynamically by command from the engine computer (DME). The scheme is achieved mechanically through the use of helical (slanted) gears. The timing chain sprocket(s) of the camshaft(s) does not connect directly to the camshaft, but has an inner hole larger than the camshaft end. There are opposing direction helical gears at the sprocket inner hole and the camshaft end. An independent splined shaft (cup) inserts between the sprocket hole and camshaft end and connects the two components. The splined shaft (cup) inner and outer surfaces have helical gears with opposing directions which correspond and mate to the sprocket hole and camshaft end helical gears. The insertion/extraction (in/out) of the splined shaft causes the relative rotational position of the sprocket to the camshaft end to change. This implicitly causes rotational position change (time shift) between the camshaft and crankshaft (connected to the camshaft sprocket via chain). An insertion of the splined shaft causes the camshaft to rotate proportionally forward causing a timing advance (earlier). An extraction of the splined shaft causes the camshaft to rotate proportionally backward causing a timing retard (later). The vanos is a devise that attaches to the front of the engine at the camshaft end, sprocket, and splined shaft. Controlled by the DME (electrical), it utilizes engine oil/pressure to manipulate the position of the splined shaft (valve timing). The vanos incorporates a piston which is bolted to the end of the splined shaft. The piston sits inside a cylinder. There are cylinder/piston enclosed oil chambers at the fore and aft of the piston. A vanos valve controls the flow of pressurized engine oil into the two opposing chambers. The valve position is manipulated by a solenoid which is controlled electrically by the DME. The DME controls the oil pressure in the opposing cylinder/piston oil chambers to position the piston, and thus control the valve timing. The DME receives piston / splined shaft / camshaft position feedback from the camshaft position sensor. Both intake and exhaust sides incorporate the same configuration scheme and the DME controls both independently.The traditional structural scheme for implementing EGR (exhaust gas recirculation) is to circulate exhaust manifold gases back into the intake manifold. This method can be termed “external” EGR. The E39 i6 with double vanos does not implement an external EGR scheme. Due to the time shift abilities of the vanos, valve timing can be manipulated to allow for exhaust gases to remain in the cylinder after combustion and be mixed in with the next cycle intake air/fuel mixture. This scheme is referred to as “internal” EGR. It’s an efficient scheme, but is highly reliant on the proper function of the vanos for effective variable valve timing. Here is the <a href="http://forum.roadfly.com/threads/11027162" target="_blank">source article</a> where we can see the actual photos of VANOS mechanism http://members.roadfly.com/rajaieq/IMG_1939%20(Small).JPGhttp://members.roadfly.com/rajaieq/IMG_1941%20(Small).JPGhttp://members.roadfly.com/rajaieq/IMG_1943%20(Small).JPGhttp://members.roadfly.com/rajaieq/IMG_1951%20(Small).JPG</blockquote>

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