Water spray intercoolers is a proven technology. Example, Evo 3 engine comes with a water spray intercoolers. The spray nozzles are mounted on the bumper. i would say the stock intercoolers are definitely sufficient for stock condition engine + bodykit(bumper). But things changes as u start to modify.
Theory is simple. As boosting, pressure begins to build up along the intercooleer piping + intercooler. Temperature builds up as well. High temperature air = low density = less oxygen. So, boost higher, get a more efficient intercooler lor...
calculation can be made. But the calculation are mostly based on ideal condition where all the environment factor are controlled. At the end of the day, it depends also on the efficiency of the intercooler that is determined by, fin design, material, material thickness, in/outlet diameter of the intercooler, interecooler piping size and etc. Size does matter. But efficiency matters more.
had a recent case posted. A waja GSR having problem with boost after installing a walbro fuel pump. tried alot of method and solutions suggested. Finally, problem solved after removing the signal light for the cool air to reach side mount intercooler that is hidden.
Finally, i'd say that the intercooler size don't affect so much of a lag... Turbine size do. I'm on a 1.6 BOT with EVO 3 intercooler + piping. Cause last time use EVO 3 engine in my car, since the intercooler piping is already there, use only lar... Well, not as bad as I've expected in terms of lag.
