BMW M5 Wartungshandbuch PDF herunterladen (Seite 30)

Box-type tappets

Compared to bucket tappets, box-type

tappets permit a substantially greater crown

curvature, resulting in decreased migration of

the cam and tappet contact point. An

alternative is concave grinding of the cams.

This, however, involves higher production

expenditure and produces a bucket tappet

with a considerably larger diameter and

therefore an additional weight of approx. 20 g

per tappet. The valve timing gear of the S54 is

still unsurpassed with regard to the moved

masses, however, the box-type tappet of the

S85 represents an optimum solution in terms

of conflicting objectives such as ease of

servicing, production engineering and moved

masses.

Valves

Both the exhaust valve as well as the intake

valve are designed as solid stem valves with a

stem diameter of 5 mm. The intake valves are

made from the valve steel X45CrSi9-3. The

exhaust valve stem is also made from

X45CrSi9-3 and is friction-welded to the valve

head made from NiCr20TiAl.

To improve the cylinder charge, the standard

cylindrical runout is not formed on the exhaust

valve in the area of the valve seat but rather the

70° bevel has a pointed runout. For this

reason, the intake valve should be handled

with great care as any "knock" could inevitably

cause damage to the edges.

VANOS High pressure pump

The high pressure pump is designed as a

radial piston pump with five pump plungers. It

is driven via a gear mechanism directly by the

crankshaft. To avoid gearing noise, when

mounting the sprocket of the high pressure

pump, the coated part must face towards the

crankshaft without any clearance. The correct

gear clearance is then established

automatically by the coating scraping off.

The high pressure pump receives it oil supply

from the bedplate. An 80 µm fine filter is

installed in the transition hole from the

bedplate to the high pressure pump. This filter

has the sole purpose of holding back any

impurities that may accumulate during series

production and is not replaced during vehicle

operation.

A feed valve in the high pressure pump

ensures a constant supply of oil over the entire

pressurized engine oil range.

4 - VANOS High pressure

pump

5 - Coated segment of high pressure pump gearwheel

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