Engine Design Philosophy

[Matt Suffern]

Someone explain this to me.  Looking through the parts catalog I study
the valvetrain diagram for the 3B.  I notice Audi has retained a
timing belt design with a simplex chain to link the exhaust camshaft
with the intake.  My BMW 525's M50, by contrast, has a duplex timing
CHAIN with, again, a simplex chain linking camshafts.

Both engines can last upwards of 300K miles.  So why the overkill on
BMW's part?  Four more valves to operate (1 more cylinder)?  Or did
they just assume people aren't going to do regular maintenance like
timing belt changes?  It just seems like an awful lot of added
complexity and valvetrain inertia to avoid a procedure most people
assume is going to have to be done anyway.

Curious.


Matt
Winston-Salem, NC
www.spannerhead.com