This came up on here recently and I'll say the same now as I said then (which is very much against the grain) - every engine builder / performance specialist I've spoken to about my (now previous) performance turbo cars have guffawed at the ideas of turbo timers and letting turbos cool in this age of water cooling and better oils. The bi-turbo unit in the a6 certainly has a water cooling element - not sure about the 2.0's but I'd imagine they do.
It absolutely does no harm to let your car idle to 'cool down' but in my opinion we're long past the days where this should be a concern.
Regarding the failure rate of modern turbos I think this can be more down to :
- The fact there are in general a far, far higher proportion of cars on the road with turbos now. Turbos will fail so by that token we'll hear about it more.
- Extended / 'long life' official oil service intervals. That's a whole different subject in itself..
I wouldn't worry about it at all. I've owned a half dozen turbo cars over the years and never had the sniff of an issue. I don't personally know of anyone who ever has either - at least in unfettled form.
Regardless of if it's technically necessary I also think if you look at your average drivers journey it would be reasonably rare to be ragging the behind off your turbos and then coming to an immediate complete engine off. Most journeys will likely have an element of time towards the end where the driving is, by nature, gentler for a few minutes.
