FMIC 2.5" 0r 3"

What is the difference between using a 2.5" or a 3" inter cooler piping. Is there more pressure in the 2.5" one, which is the better?

The better one is as small as you can get away with.

Chunking a FMIC in front of the rad is going to cost you flow through the rad. The bigger you put in front, the less cooling you're going to get.

...2.5" or a 3" inter cooler piping. Is there more pressure in the 2.5" one, ...

the smaller pipe will create a higher pressure reading.

That's what pressure is, the result of a flow restriction.

One's half an inch bigger than the other.

Let's look at it from another angle: one is half an inch smaller than the other

Let's look at it from another angle: one is half an inch smaller than the other

True, but I'm a half an inch bigger kinda guy.

Nevertheless, keep wearing those lead pants, you never know what's around the corner...

I think smaller piping helps response.

I think smaller piping helps response.

Or does a bigger pipe help spool up as there is less restriction for the compressor to 'push' air against??

Pressure build up will be slower (due to the bigger volume), but mass flow will be higher and spool will be faster??

I think this has been covered before, but a bigger pipe and less restrictive intercooler is better in terms of efficiency as it allows the mass of air to move through the bigger volume of intercooler and pipework at a lower density, allowing for better heat transfer and lower pumping losses due to the restriction, which gives lower temperatures out of the compressor to start with?

Most big power car with FMIC seem to have 2.5inch from turbo to IC and 3inch from IC to inlet plenum