Replacing intercooler piping

[Old.Tony]

The velocity of the air is directly related and proportional to the volume of the pipe and the pressure of the air (Fluid Dynamics 101).

The restriction point is the turbocharger (and inlet valves). As long as anything between the turbo and the inlet manifold is larger than the turbocharger, you'll still get the same number of molecules into the combustion chamber.

Assuming constant pressure (boost) - making the pipe smaller will increase the velocity of the flow. The flow won't be inhibited or assisted by changing pipe sizes.

For the technically minded/curious ...

In accurate calculations, there are also laminar flows to consider, and small pipes are more restrictive than simple volume calculations would allow for, but with the standard size we have you won't see that coming into play too much except inside the intercooler.

Laminar flow describes how a gas/liquid flows close to a surface. Molecules that are actually colliding with the surface of the pipe move very slowly, slowing the molecules a little further away. Thus in a very small pipe, laminar flow is almost entirely the reason why you can't blow heaps of air through it, or pump lots of water. With the size of the inlet piping we have in our vehicles, it's safe enough to disregard that in your calculations.

 

[MAD D40]

That makes sense so your saying in engrish as the pipes and turbo are large enough to provide the engine with sufficient air making them bigger will have no effect.

I dont know what you do for a living but you seem rather cluey about this.
So if increased piping makes no difference why is ballooning rubber pipes decrease throttle response would it be similar to larger pipes?
Or is it because the force required to balloon the pipes is weaker than the force it takes to pass the inlet valves into the combustion chamber?

 

[Old.Tony]

The problem there is in pressure delivery. If the pressure's being used to expand the pipe, it's not going into the engine. Larger pipes would have to be stiffer to prevent the same thing from happening.

Some of the guys replace the intake lines particularly because the turbo can suck so hard (especially with a partly blocked or dirty air filter) that the intake pipe collapses, causing poor throttle response. This section of hose is something that I will be upgrading myself, one day.

Using those blue silicon hoses for the sections between the turbo and the intake is a good idea, because they have webbing laminated into them to prevent ballooning.

As for what I do ... I did a bit of engineering back in the day. I do other stuff now. Mostly, I read buckets of information about whatever I'm interested in and absorb a small amount, which is handy when I can actually remember it because then I can type it back out. I'm not really all that clever - just well-read.