wouldn't it make sense to have a larger pipe going from the turbo to the IC and then a slightly smaller pipe going from the IC to the TB? or in his case his turbo outlet is kinda small so like go with 2" both ways. But if your turbo was bigger like say a 3" or 3.5" outlet having a slightly smaller pipe going to the TB like say a 2 1/2" or 3" would have more velocity right? It would also be compressed which would give you more boost correct? It seems to me like your boost would be more efficient that way. just my two cents.
ok, how does this sound, i already have 2 1/4 inch pipe so i amgonna run that from the turbo to the ic and then from the ic to the t/b i will run 2 1/2 because thats what it is goin into the t/b, sound good everyone?
sp what your saying bill is.... you should go with the same diameter from the exit of the turbo to the intercooler? correct? then step it up to 21/2 inch piping to from the intercooler to the throttlebody?
the only reason i said 2 inch from turbo to i/c is cuz thats the same diameter of the outlet of the turbo. The only reason i said 2 1/2 inch form i/c to tb is because the tb has a 2 1/2 inch inlet. i you you use an expanding pipe you lose velocity and pressure drop, just like what bill said.
I know everyone believes the myth that bigger pipes will increase flow, but it is just that-a myth. The flow rate into an engine is determined by displacement X RPM/2 X VE. Generally, bigger pipes will NOT increase VE, so it doesn't increase flow. But increasing pipe size WILL DECREASE velocity. And going from any pipe into a larger pipe means the gas expands (loses density) at the transition. And in the case of a boosted engine, bigger plumbing means more "accumulator effect", so there actually is some loss of response (more lag).
As long as the pipe is adequately sized there is nothing to be gained with a bigger pipe. This is true for any fluid-air,water,etc. Any piping system has an "optimum size", based primarily on pump flow and overall length. There is NO BENEFIT to exceeding this optimum size. Almost all of the restriction in an automotove intake/exhaust system is caused by turns, irregularities, and other restrictions, not by the piping itself. Think about how limited (and irregular) the area under that valve is. Your worrying about getting air through a 2" pipe, but it has to pass through that limited area around the valve. So what you really need is velocity to help it slip through that restriction.
As a generalization, automotive induction systems generally get smaller as you move from the air intake (filter box) to the manifold, in order to increase the air velocity.
Say you have a 2" pump with a 2" inlet port and a 2'' discharge port, with a rated flow of 100 GPM. You can put a 4" pipe on the inlet, and 4" pipe on the discharge, but it will still pump 100 GPM.
Its the same with wire in an electrical circuit. A 15A ( fuse or breaker) circuit is adequately served with a 14 ga. wire. You can install a larger 12 ga wire, which is capable of carrying 20A, but the circuit ampacity (flow) is till 15A.
Now I know I'll get a lot of crap about this, because the whole aftermarket group that pushes intake and exhaust products is premised on the "bigger is better" myth, but its still a myth.