Lotus Elise S1 Service Notes page 132

ENGINE
OPERATION
The K Series engine is built up from aluminium
castings bolted together. These consist of three
major castings; the cylinder head, cylinder block and
a bearing ladder which is line bored to provide the
main bearing bores. Attached to these are three
minor castings; above the cylinder head, the
camshaft carrier and the camshaft cover. Below the
bearing ladder is an oil rail.
Each of the ten cylinder head bolts passes through
the cylinder head, cylinder block and bearing ladder
to screw into the oil rail. This puts the cylinder head,
cylinder block and bearing ladder into compression
with all the tensile loads being carried by the cylinder
head bolts.
When the cylinder head bolts are removed;
additional fixings are used to retain the bearing
ladder to the cylinder block and the oil rail to the
bearing ladder.
K8 engine: The cross flow cylinder head has two
valves for each cylinder and the spark plugs set at
an angle. The inlet ports are of equal tract, designed
to ensure a balanced mixture throughout the speed
range to improve combustion and reduce exhaust
emissions. The single, overhead camshaft operates
both inlet and exhaust valves via hydraulic tappets
and is driven from the crankshaft by a timing belt.
Belt tension is maintained by a spring loaded
tensioner. The camshaft is retained by a one-piece
camshaft carrier sealed and bolted to the cylinder
head. Positive location is by means of a flange
which also controls camshaft end-float.
K16 engine: The cross flow cylinder head is based
on a four valve, central spark plug, combustion
chamber with the inlet ports designed to induce swirl
and control the speed of the induction charge. This
serves to improve combustion and hence fuel
economy, performance and exhaust emissions. The
twin overhead camshafts operate the valves via
hydraulic tappets, one camshaft operates the
exhaust valves whilst the other operates the inlet
valves. The camshafts are driven from the
crankshaft by a timing belt, belt tension being
maintained by either a spring loaded, manually
adjusted tensioner or, on later engines by an
automatic tensioner. The camshafts are retained by
the camshaft carrier, which is line bored with the
cylinder head.
Later engines are fitted with a plug top coil ignition
system in which the conventional distributor is
replaced by a camshaft sensor located in the
camshaft carrier adjacent to the exhaust camshaft.
Camshafts fitted to some early engines and all
engines with plug top coil ignition have an integral
reluctor ring which provides an input to the camshaft
sensor. Twin coils are fitted on top of the camshaft
cover, each coil supplying ht voltage to one pair of
spark plugs.
Variable valve control (VVC): This system is fitted to
some K16 engines. VVC is designed to provide
variation in the valve open and close periods by
independent positioning of the two inlet camshaft
assemblies thereby giving optimum low speed
driveability with no detriment to high speed
performance.
DESCRIPTION AND OPERATION 111