The 2.0 litre 16 valve engine in my 1994 Audi Coupe had one cam driven by a
front belt and the other by a rear chain. The chain wore slack on those
engines and idling they sounded like an old sewing machine.

Colin M
www.sportimport.co.uk

They're starting to go back to chains now. I believe all the Audi V6 and V8
are now chain and some of the 4 cylinders too e.g. 1.8TFSI and 2.0TFSI IIRC.

FYI, the VR5, VR6, W8, W12 and W16 are all chain driven.

I believe most manufacturers went to belts in order to have quieter engines
but obviously they add a big cost to maintenance every few years and are
less reliable.