Lotus Elise Service Notes page 133

ENGINE
Whilst the exhaust camshaft is similar to camshafts
fitted to non VVC K16 engines, there are four inlet
camshafts, assembled in pairs, each individual
camshaft operating the inlet valves on one cylinder.
The front pair of camshafts are driven, via the front
VVC mechanism, by the camshaft timing belt; the
rear pair of camshafts being driven via the rear VVC
mechanism by the rear timing belt which is itself,
driven by the exhaust camshaft. Independent
positioning of each inlet camshaft is controlled by its
respective VVC mechanism. The front and rear VVC
mechanisms are connected to each other by the
control shaft. Movement of the control shaft is
controlled by the piston and rack assembly located
within the hydraulic control unit. The piston and rack
assembly moves in response to engine speed and
load signals received from the MEMS ECM via two
solenoids mounted on the hydraulic control unit
housing. As the piston and rack moves up or down
in response to the signals received, the control shaft
rotates and alters the position of the valve timing
mechanisms.
All engines: Self adjusting hydraulic tappets are
fitted on top of each valve and are operated directly
by the camshaft(s). The valve stem oil seals are
moulded onto a metal base which also act as the
valve spring seat on the cylinder head.
Exhaust valves fitted to later engines are of the
carbon break type. A machined profile on the valve
stem removes any build up of carbon in the
combustion chamber end of the valve guide thereby
preventing valves from sticking. These valves may
be fitted to all early engines.
The stainless steel cylinder head gasket has
moulded seals around all coolant, breather and oil
apertures and has steel cylinder bore eyelets.
Compression of the gasket is controlled by limiters
at each end of the gasket.
The cylinder block is fitted with 'damp' cylinder
liners, the bottom, stepped half of the damp liner,
being a sliding fit into the lower part of the cylinder
block. The liners are sealed in the block with a bead
of Hylomar applied around the stepped portion of the
liner. The seal at the cylinder head is effected by the
cylinder head gasket with the liner top acting as a
break between the combustion chamber and gasket.
The aluminium alloy, thermal expansion pistons
have a semi- floating gudgeon pin which is offset
towards the thrust side and has an interference fit in
the small end of the connecting rod. Pistons and
cylinder liners are supplied in two grades. Big-end
bearing diametric clearance is controlled by three
grades of selective shell bearing.
The five bearing, eight balance weight crankshaft
has its end-float controlled by thrust washer halves
at the top of the central main bearing. Bearing
diametric clearance is controlled by three grades of
selective shell bearing. Oil grooves are provided in
the upper halves of main bearings No. 2, 3 and 4 to
supply oil, via drillings in the crankshaft, to the
connecting rod big-end bearings.
DESCRIPTION AND OPERATION 18