Chain vs Cambelt

Author
Discussion

anonymous-user

53 months

Tuesday 17th November 2009
quotequote all
From this thread it appears that generally chains are better, except for in VAG cars which are just poorly engineered st hehe

As a side note, I was quite impressed to find that the chain in the V6 Diesel as used in Jaguars doesn't need the belt changed until 110k miles. It appears not to be lies either - mine was changed at 110k miles and appeared to be fine. The secondary belt that just drives the fuel pump is up for renewal at 150k.

To a certain extent this erodes the longevity advantages of chain drive, as for the typical car it'll need doing only once in it's life. Belts do have the advantage of lower weight, somewhat lower noise, easier packaging perhaps (looking at the route this belt takes you couldn't do it with a chain) and probably some other things too.

Dave

chris7676

2,685 posts

219 months

Wednesday 18th November 2009
quotequote all
Attention: The MX-5 have cambelts (at least 1.6 mk1) - changed it myself so I do know.

JB!

5,254 posts

179 months

Wednesday 18th November 2009
quotequote all
was8v said:
JB! said:
tensioners grenade too, common on the 12v vr.
Hardly common at all.

You can sometimes hear the tensioners rattling a little over 100k miles though.
so why are they changed then?

if the tensioners and chains will last the life of the car?...

if VAG had chains nailed, the 20v lump would run one... but it doesn't.

smallgun

256 posts

232 months

Wednesday 18th November 2009
quotequote all
Why do we still use cam belts or chains to open and close valves. I would have thought by now we would be totally hydraulic. I've got half a memory of some Americans building an engine that used a hydraulic system some time ago.

anonymous-user

53 months

Wednesday 18th November 2009
quotequote all
Yes, in theory you could get rid of all the weight of the cam and belt/chain. I don't think anyone's done it in practice though as even F1 engines use hydraulics/pneumatics in place of the conventional springs with all the other gubbins being retained.

The catch with moving away from a mechanical system is even if you can get it work fast enough any failure of any component is likely to leave a valve dangling down when the piston's coming up! This is not a good thing - as the owners of many "interference" engines have discovered if their belt snaps.

Ducati's gone the opposite way. It's desmodromic system opens and closes the valves by direct mechanical action. The engine wastes no energy compressing valve springs and valve float is eliminated.

turnipbmw

65 posts

172 months

Wednesday 18th November 2009
quotequote all
but the Ducati cam is still turned by a belt - indeed one of the most fragile on the market.

My mates 916 has its belts changed by the dealer yearly even if he has not used it.

The old models used a shaft though ie singles and 900ss from 1977