Rover K-series Variable Valve Control (VVC) T he VVC principle is based on an eccentric rotating disc to drive the inlet valves of every two cylinders. Since eccentric shape creates nonlinear rotation, the opening period of the valves can be varied by controlling the eccentric position of the disc. The basic concept was developed by a mr. Mitchell and it was published and patented back in 1973. However no one used it and it was forgotten until Rover re-discovered it. In 1989 Rover began experimenting with the system and in 1993 had developed a 1.4 litre version with VVC. With VVC the outlet camshaft isn't part of the VVC system and is driven normally by the toothed belt from the crankshaft. If Rover would have driven the entire camshaft from one eccentric disc then only one cylinder would benefit from the speed variation. For one cylinder the camshaft would run at low speed when opening the inlet valves giving long duration and when the valves would be closed the camshaft would run at a higher speed. Now the inlet valves on the same camshaft for another cylinder would run fast when the inlet valves were opening and would run slow when the valves were closed. Totally unacceptable! So every cylinder needs to be driven from the eccentric disc seperately! For the K-series Rover opted for two eccentric disc's whereby each disc is driving the inlet valves for two cylinders. The picture of the VVC head explains things. l The lower cam is the outlet cam driven from a toothed belt (belt not mounted in the picture). l The first eccentric disc at the top left is also directly driven from the toothed belt l The second eccentric disc at the top right is driven from the outlet cam by a separate toothed belt (the belt at the right side of the head) l The first eccentric disc (topleft) drives the inlet camshafts for cylinders one and two l The second eccentric disc (top right) drives the inlet camshafts for cylinders three and four In principle every cylinder has it's own cam. l The camshaft for cylinder one is driven by eccentric disc no. 1, it is hollow to allow passage for the cam of cylinder two. l The camshaft for cylinder two is driven by eccentric disc no. 1 it is running partly through the hollow camshaft of cylinder one