Cars with DSG boxes - Do they break cambelts sooner?

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Mon 20 May 2019 12:57
Cars with DSG boxes - Do they break cambelts sooner? - John F

Do the almost instantaneous gear changes result in abnormally high stresses on the cambelt teeth when the crank cog teeth rapidly decelerate the belt, and the belt teeth rapidly decelerate the cam cogs when changing up - and vice versa when changing down? Is this why some manufacturers reduced the advisory change intervals? These boxes must unduly strain chains as well, no? I always thought automatic gearboxes protected the engine from harsh and unsympathetic drivers but now I'm not so sure. Perhaps this effect is offset by the many gears such boxes now have, so that the r.p.m. change between the gears is less?

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Mon 20 May 2019 13:09
Cars with DSG boxes - Do they break cambelts sooner? - RT

Your last sentence says it all - the difference in rpm is relatively small.

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Mon 20 May 2019 13:41
Cars with DSG boxes - Do they break cambelts sooner? - SLO76
Interesting theory John but I haven’t seen any real evidence that it impacts the timing belt/chain lifespan. Early DSG equipped TSi VAG products are prone to timing chain failures but this effects the manuals equally as far as I know. It’s the complexity of the gearbox that causes problems within itself and few owners maintain them properly with fluid changes on schedule.
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Mon 20 May 2019 15:45
Cars with DSG boxes - Do they break cambelts sooner? - Engineer Andy

From reading HJ's reports and columns, it seems that much of the problems are related to people regularly using them to creep at slow speed in heavy traffic, to tow or drive up steep sloped driveways at slow speed, wearing the clutches because the system slips the clutch just like in a manual.

IMHO, dual clutch gearboxes were always designed with performance and efficiency in mind, and not slower speed manouvring or towing. Admitedly its an extreme case, but I thought that's why F1 cars can burn out their clutches if they hold too long on the start line, given it only occurs sparingly during a race. Real world cars obviously are more robust in that regard, but still.

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Mon 20 May 2019 23:55
Cars with DSG boxes - Do they break cambelts sooner? - CHarkin

The DSG changes gear ultra quickly but it is cushioned by a clutch the same as in a manual car. By far the greatest load on the valve train is during high revs, inertia of the valves and the cam followers increases load in proportion to revs. This is why highly tuned racing engines need a light weight valve train and why overhead cam engines can rev higher than overhead valve engines, no rockers to rattle up and down 5000 times a minute.

Edited by CHarkin on 20/05/2019 at 23:56

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Wed 22 May 2019 08:24
Cars with DSG boxes - Do they break cambelts sooner? - nick62

no rockers to rattle up and down 5000 times a minute.

Or 16,000 times a minute in motorbike engines. Not bad though when you can get 130+ hp out of a 600cc motor.

Edited by nick62 on 22/05/2019 at 08:26

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