Why Timing Chains

[Dub Style 0]

Just wanted to know what are the benefits of having a chain as opposed to a belt, i mean when somone would mention timing chain the only thing that would come to mind is rattly fiestas so why has this system been used in the vr

[stevemac 0]

Quite simle - timing chains are far more stronger & reliable than cam belts.

 

Belts can & do snap without notice & tensioner pulleys seize. Certain VW engines do suffer from cam belt failure, whereby the belts regularly snap before the service interval at which they should be replaced !!

 

Mercedes do not & will not use timing belts on any of their engines for the above reasons.

[Kevin Bacon 5]

The main reason for the chains on the VR was two-fold:-

 

1) Strength as Steve mentioned and long service life. VW were also looking at a diesel VR6 and the torque from the crank would probably overwhelm a cambelt.

 

2) Compactness. The VR would need a very wide cambelt to handle the torque and consequently wouldn't fit in the engine bay of the Corrado.

 

The current Audi S4 V8 also uses chains, as does the E36 M3 engine. It's a proven technology with quieter running and virtually maintanence free.

[Dub Style 0]

Mercedes do not & will not use timing belts on any of their engines for the above reasons

 

Blimey that is somthing new for today

cheers Steve & Kev

[Guest]

The reasons stated above are why the VR6 uses timing chains but they are far from maintenance free. The VR6 uses plastic / plastic lined tensioners and guides that will wear out and allow eccessive play and if left long enough it will allow the valves to contact the pistons. Unlike A1 - A3 4 cylinder motors, the VR6 is an interference motor and you will destroy the top end of the motor if the tensioners wear out just like a 16V with a broken timing belt. In North America it would seem the timing chain guides will go for about 140,000 kms to 200,000 kms before the motor will sound like a cement mixer. Relpacing the tensioners & guides isn't all that hard but the tranmission will need to be removed to do this.

 

Cheers, Dennis

[Kevin Bacon 5]

Indeed....but 100,000 miles is the ball park figure for chain/tensioner replacement, which is considered maintanence free in VW's eyes....in fact they don't even specify a service interval for the chains...which is ironic given they've redesigned the upper tensioner 5 times and the cam sprocket chain assembly twice.

 

I have replaced the upper tensioner pad with the later MK4 item which last a lot longer than the old resin coated steel pad.

[2cc 0]

Yep, just done mine at 123,525 miles. Top tensioner was well worn, but no noticeable ill efects on running. Hopefully the new parts will last even longer than this.