i am going to be using a 14b for my turbo set up and i was wanting to know how big of exhaust i will need and why.

 

You would be ok with 2.5" exhaust

I? would recommend a 3" due to the decrese in spool time and the increase in power

 

3inch OPEN DOWNPIPE

 

why 3 in. tho 3 in. is biger then the outlet of the turbo?

 

Turbos love to flow and there is already enough back pressure produced insdie the turbine housing

 

i know that but what i am looking for is how dose the air flow better going from the outlet of the turbo (lets just say it is 2in.) to i big 3 in turbo. why not just stay 2in. all the way back?

 

It isn't just the initial size. Exhaust cools and expands as it does so. An ideal exhaust would start out small and gradually increase in size. The cheaper method that is almost as good is to just make the whole exhaust big.

 

Just becaseu the outlet of the turbine housing is 2" doesn't mean that it is sufficient to flow the volume your engine is producing