2. turbo thru a 3. intercooler back to 2.5

[carbite]

turbo is 2. out. then to a 3. water/air intercooler. then  to 2.5.
whats the positives and negatives of doing this?

[BeetleBug]

turbo is 2. out. then to a 3. water/air intercooler. then  to 2.5.
whats the positives and negatives of doing this?

Loss of airspeed.

[Airspeed]

I think the loss of airspeed is not much of a concern in the example described. The cu-ft in and out remains the same. The turbulence from such transitions is what will cause a little resistance. However, the reduction in airspeed when the flow gets into the "huge" box which is called the intercooler, will be much, much bigger and that causes hardly any problem either. So, as long as these changes in cross-sections are not smaller then the 2" out of the turbo (in this example), its not a problem at all.
The only thing that you might feel, is that bigger tube sizes after the compressor will increase 'plenum'-volume, which could increse turbo-lag/response a little. No biggie usually in my experience.