Stock S5 13BT is it really necessary to use a BOV on a turbo car? or

 

Your 13BT already has a bypass valve from the factory. It blows into the TID just after the AFM. There really isn't any benefit to fitting an aftermarket valve besides the noise.

 

Doesn't venting into atmosphere cause a rich condition, and send fuel into your exhaust, damaging cats or shooting flames out the exhaust? I believe I read that somewhere on this site...

 

What if the cars not stock and running around 350 to 500 hp then would it be necessary,I mean why do people run them in the first place?

 

when ur under boost and u suddenly close the throttle, that pressure needs to go somewhere. it can't go into the intake, the throttle is closed. that's what the bov is for.

 

Basically, yes. The stock ECU has already metered the air that exits through the BOV, so it dumps way too much fuel. Stock ECU cars with open BOVs generally recover from shifts poorly and blow flames. This is why the stock BOV vents back into the TID after the AFM.

350HP to 500HP is a huge spread. You cannot compare the two.

People run open BOVs because they like the noise, pure and simple. I run an open BOV on my car because my car was never equipped with a BOV from the factory (NA and all).

 

Do you control your boost pressure with the BOV or the wastegate?

 

Wastegate.

 

so is there any reason to upgrade the wastegate? would it allow you more range of boost pressure to mess with?