I searched but did not get a clear answer, What is the diffrence and purpose? Please help out a noob.

 

Its all about gross air flow and resistance in a certain size pipe. If you run a smaller IC pipe, you have less empty space to fill so you reach full boost sooner, BUT you can't flow as much air through it. On the other hand if you run a larger diameter IC pipe, you can push more overall volume through it, but since there is more void to fill, it takes longer to reach full boost.

 

for a street car with up to 400whp 2'' is fine.

 

Eh, I think 2'' is a little small, 2.5'' is a lot more suitable imo.

 

ehe

 

2.5" on the cold side and 2" on the hot side of the IC piping.

 

i never run anything smaller than 2.5 inch unless it wont psychically fit

 

for a 650hp application with a 6262 .63ar. should i run 3 inch on both sides of ic?

 

No. 2.5" for both sides of the Intercooler is just fine.

 

I made 670whp at 26psi with 2.5 inch charge piping and a 64mm throttle body...