Which is it, 7 lb or 20 lb? The Cobalt SS runs 20+ psi but that is not your average turbocharged setup. We use 5 psi on an application that is used in an environment where it would destroy most vehicles.
Mazdaspeed3's run into problems at 15 psi, and WRX's/STI's are blowing turbos and pistons with less boost.
Your average turbocharged application would be something like the Ford/Volvo T5, Saab's, and Audi 4-bangers. They are designed for longevity rather than performance.
both. depends on the engine. for diesels 20lbs isn't anything. stock evos run 20lbs from the factory, i believe. stock SR20DET's run 7ish and can run around at 14psi wth no problems at all. same with supras and other well designed factory turbo engines. the new genesis has an engine rated for 29psi and the turbo maxes out around 14psi.
a turbo can do whatever you want it to, its the engine that is the weak point. if you push a little turbo way passed its efficiency range you're asking for trouble. the only time a turbo fails is:
1. people beat on them and dont let them heat cycle before they shut the car off which takes all of a minute or so. this isn't really a big deal these days with the sophisticated cooling technology available.
2. an engine frags itself which kills the turbine wheel which frags bearings which means you need to rebuild a snail.
the problem with turbos is that they aren't idiot proof like blowers and they have a little lag especially if its a power dependent part and not a power adder (like a supra vs a TT viper). with the advent of variable geometry turbos like in the 911 turbo and other cars lag is no longer a problem either.
everything from smart cars to snowmobiles rock turbos from the factory. blowers are cool but turbos have the advantage especially when a company puts all that time into making the systems cost effective and compact.
then you get into the fuel economy aspect of it all. the primary advantage of turbos is that they work when you want them to and not when you dont. aside from camgear equipped blowers this can't be said for superchargers.
meh, this is useless. i like both, you guys dont like turbos. i get it. whatever.