Cylinder Heads - Audi 4.2-liter V8 FSI Service Training

Engine Mechanical

Cylinder Heads

The cylinder heads are similar in design to the Audi V6
four-valve FSI cylinder heads.
Specifications
– Aluminum cylinder head
– FSI intake ports with horizontal divisions to produce a
tumble effect
– Four-valve technology with centralized 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 actuation
via roller cam followers with hydraulic backlash
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 pins when the
camshaft is at a standstill; intake in advance position,
exhaust in retard position
– Return spring in exhaust camshaft
– Implementation of "internal exhaust gas recirculation"
through the use of a corresponding 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 optimized (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 rocker arms 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 lifters were adapted from the 3.2L V6 engine found
in the TT and A3. 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, thereby reducing the temperatures in
the cylinder head combustion chamber plate.
– Due to a modified camshaft drive reduction ratio, the
camshaft adjuster has 25 teeth for the chain drive, as
opposed to 30 teeth in the basic engine.