Originally Posted by Got_Diesel
We have turbos that boost to 26 psi. A ram air will not make much difference if any at all. Just like a cold air on a turbo doesn't do much either because the air still gets warmed through the turbo and cooled through the intercooler. that turbo will pull all the air it can.
Unlike an N/A motor where you need to get as much as you can in with help.
It has been demonstrated on the 335i via numerous back-to-back dyno testings and intake comaprisons that a true CAI is a benefit resulting in hp gains. Hotter airgoing into the turbo isin a less condensed form. If that air is colder it is densor and the output temps are also likey to be cooler irrespective of the fact that there might some thermal gain after running through the turbos. The same concept applies when running an open air filter element - the heat of the engine bay gets sucked up and can actually result in a loss of power.