Lotus 2004 Eleven Service Notes page 142

Lotus Service Notes
VALVEMATIC System
The principle of the VALVEMATIC system is that a conventional inlet camshaft with a single (rotary) cam
for each cylinder operates a roller arm on a pivot shaft. On each side of the roller arm is an oscillating cam,
each of which opens, via a finger follower, one of two conventional inlet valves for that cylinder. The two valves
are operated at all times as a pair. The connection between the roller arm and the two oscillating cams is made
via a common pivot sleeve machined with three separate sections of helical splines, which correspond with
splines in the bores of the roller arm and oscillating cams. By sliding the sleeve axially, within the roller arm
and cams, the opposite helix angle used for the cams compared with that for the roller arm, results in a phase
shift between arm and cams.
Valves shown at full lift (camshaft omitted for clarity)
Pivot shaft
Oscillating cam
Finger follower
Hydraulic
pivot post
A 'lost motion' damper ensures that the roller arm stays in contact with the rotary cam profile at all times.
The position of the oscillating cams at the start of a valve opening event however, is dependent on their phasing
with the roller arm. In the low lift mode, where the cams are phased counterclockwise in relation to the roller
arm as viewed from the rear, the finger follower roller is in contact with the base circle of the oscillating cam,
which must turn through a large part of its range before the cam starts to lift the valve, resulting in only the first
portion of the cam profile being used. In high lift mode, the oscillating cams are phased clockwise in relation to
the roller arms such that the cam profile immediately starts to lift the valve as soon as the roller arm is depressed
by the rotary cam, continuing then to utilise the full profile of the oscillating cam for maximum lift.
The concomitant variation in valve timing as the lift changes, is managed by the separate VVT-i system
(see earlier).
Section EH
Roller arm
Camshaft
operates against
this roller
Inlet valves
Page 19