Cylinder Head - Audi 4.2-litre V8 FSI Service Training

Engine mechanicals

Cylinder head

The cylinder heads are based technically on the
well-known Audi four-valve FSI cylinder heads.
Specifications
– Aluminium cylinder head
– FSI intake ports with horizontal divisions to
produce a tumble effect
– Four-valve technology with centralised layout of
the spark plugs
– Inlet valve: chrome-plated solid stem valve
– Exhaust valve: chrome-plated sodium-filled
hollow stem valve
– Valve lift 11 mm
– Lightweight, low-friction valve gear, valve actu
tion via roller cam followers with hydraulic back-
lash compensation, single valve spring
– Two assembled camshafts per cylinder head,
driven by hydraulic swivel motors
– Intake valve opening angle 200 crank angle
degrees
– Exhaust valve opening angle 210 crank angle
degrees
– Adjustment range of the camshafts is 42 crank
angle degrees
– The adjusters are locked by locking bolts when
the engine is at a standstill; Intake in advance
position, exhaust in retard position
– Return spring in exhaust adjuster
– Implementation of "internal exhaust gas
recirculation" through the use of a correspond
ing valve overlap
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Different features of the high-revving engine
To match the higher engine power output and RPM,
the following cylinder head components were
modified:
– Intake ports are charge optimised (based on
larger cross-sections)
– Intake valves are chrome-plated hollow stem
valves (for weight reduction)
– Valve springs are made of a material with higher
tensile strength and also have higher spring
force
– To meet the higher fuel requirements the
injectors are designed for higher flow rates.
– Roller cam followers are more robustly designed,
with peened rollers for higher strength
– Camshafts have different timings and larger
opening lengths
– Intake valve opening angle 230 crank angle
degrees
– Exhaust valve opening angle 220 crank angle
degrees
– The clearance compensation elements were
adopted from the VR6 engine. They have a larger
ball stroke which, in the course of testing,
proved advantageous for the high-revving
engine (with regard to the inflation of the
hydraulic valve clearance compensation
element).
– The cylinder head has a modified water jacket
which circulates coolant to the area between
the intake port and the injector and thereby
reduces the temperatures in the cylinder head
combustion chamber plate.
– Due to modified camshaft drive reduction ratio,
the camshaft adjuster has 25 teeth for chain
drive, as against 30 teeth in the basic engine.