The thing is that due to the helical cut splines, vanos piston moves linear to rotate the cam, and when we turn the cam then it could also move the vanos piston linearly. So even with the hub bolts loosen, turning the cam CW could pull the vanos piston.
Another point is that, what if the cam timing is off (i.e the bridge off the head by 2mm on the exhaust side) was due to the vanos piston was not its most retarded position (off from the cap end travel)? And so in this case, loosening the hub and turn the cam to the correct timing still ended up wrong because vanos is not its most retarded position.
So how does the OP know if the vanos pistons are at their most forward position when he just loosen the hub and correct the cam timing? Obviously he could do a trial-error of loosen the hub and correct the cam, then do a final turning the crank 2 turns then check the cam bridge at TDC, and repeat until the timing is correct.
Another point is that, what if the cam timing is off (i.e the bridge off the head by 2mm on the exhaust side) was due to the vanos piston was not its most retarded position (off from the cap end travel)? And so in this case, loosening the hub and turn the cam to the correct timing still ended up wrong because vanos is not its most retarded position.
So how does the OP know if the vanos pistons are at their most forward position when he just loosen the hub and correct the cam timing? Obviously he could do a trial-error of loosen the hub and correct the cam, then do a final turning the crank 2 turns then check the cam bridge at TDC, and repeat until the timing is correct.
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