Porsche Cayman User Handbook Manual page 18

Two-stage resonance intake 'resonance' pipe connecting the
manifold. twin plenum chambers is used
to alter the geometry within the
The intake manifold has a twin-flow manifold. The resulting vibration in
pipe with two-stage valve which the incoming air helps to maximise
opens and closes at predefined cylinder charging and create the
engine speeds. An additional optimum air/fuel mix. The results:
higher torque at low rpm, a flatter
torque curve, and greater top-end
power. It also brings an additional
dimension to the unique engine
sound.
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VarioCam Plus.
VarioCam Plus combines variable
valve timing with two-stage lift
on the inlet side. The resulting
benefits include greater power and
torque at all engine speeds, as
well as smoother running, better
fuel economy and fewer exhaust
emissions.
Essentially, the system creates
two engines out of one, switching
seamlessly between them as
driver inputs change. All operations
are centrally controlled by
the Motronic ME7.8 engine
management system. The result:
rapid acceleration and balanced
running characteristics.
The two-stage valve lift mechanism
on the inlet side incorporates
a series of electro-hydraulically
switchable tappets. Each of
the 12 tappets consists of two
concentric lifters which can be
locked together by means of a
pin when required by the engine
management system. When the
tappets are locked, the outermost
ring – which is driven by two large-
profile cams – is in direct contact
Cayman
The new Cayman and the Cayman S |
with the valve. When the pin is advanced to help minimise fuel
removed, the innermost lifter – consumption and emissions.
operated by a smaller cam lobe –
has sole influence over the To achieve maximum power and
amount of valve lift. The timing of torque, the lift is raised and the
each valve is steplessly controlled timing advanced.
by means of an electro-hydraulic
rotary vane adjuster at the head
of each inlet camshaft.
To improve responsiveness when
starting from cold, VarioCam Plus
will raise the amount of lift and
retard the timing of the valves.
At medium revs and minimal load,
the valve lift is lowered and timing
· 39 ·
Drive
VarioCam Plus