2.7T v 4.2 A6

Ti Kan ti at amb.org
Sat Jan 1 05:02:31 EST 2005

Tyson Varosyan writes:
> It seems like a step backwards to remove a light belt and install a metal
> chain. The rotational weight is the name of the game there and there is a
> big difference. Nobody here needs to sing me songs about what happens when
> the damn thing fails, I have 3 TT motors (Mitsu and Supra) that
> snapped/skipped the belt resulting in many bent valves and cracked pistons.
> I would hope that Audi would find a way to build a lighter-weight stronger
> belt rather than revert to a chain drive. If you want perfect timing, gear
> drive is for you.

The purpose for Audi switching to timing chain rather than timing belt
(and moving the whole assembly to the rear of the engine) is to reduce
the overall length of the V8 engine.  This was necessary in order to
fit that engine in the B6 chassis' small engine compartment.  This change
netted a reduction of the engine length by 52mm (just over 2").  That
might not seem like a lot, but it's just what's needed.

The weight of the chain or belt here is negligible compared to the
inertia of the camshafts and other accessories that it's driving.
The primary advantage of belt drive is lower noise, however I have not
noticed any chain noise on the new V8s.  In fact these are some of the
most glorious sounding V8s around.

Ti Kan
Vorsprung durch Technik

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