I didnt know I had done stuff at your work rc???

i was wondering about v-band the other day, and then i noticed at work the heads of all our extruders are sealed on using a similar clamping method, the don't leak at 9000psi with no gasket... so the method is certainly sound!

only time they leak is when the sealing surface has been damaged, usually by some knob trying to separate them with a hammer and screwdriver

V-bands are perfectly fine

Generally, small frame turbos and turbos with internal wastegates used bolt on flanges and larger frame, non gated turbos use V-bands.

Trucks which do millions of km's use V-band clamps, so there's no reason to worry about the exhaust and/or inlet only being held on with a clamp!

Both will flow the same as it's internal diameter doesn't change ,5 bolt will be a rigid clamp where a V band can flex a little.... Issue with V band when welded can distort the sealing surface even with tig if incorrectly done...5 bolt is best replaced with studs and nuts as sometimes bolts can seize and snap,a steel bolt that has many heat cycles builds up it's hardness and will be difficult to drill out.
If you find a v band turbo that you can't pass on but want the bolt style you can weld a flange onto the housing to convert it.....

Guys im looking at turbos at the moment and cant decide between 5 bolt or v-band,i don't like the fact that v-band is only held on with a clamp but which is better?Does one flow better than the other?