u have to measure exhaust temp as the turbo recycles the exhaust air to spin the turbine. see www.howstuffworks.com. As for the ponds, the air is compressed into 40 lbs per square inch of pressure to be sent into the combustion chamber providing condensed air into the chamber and allowing for higher compression.. i.e. more power. Now if the pressure is too high for the chamber u have the pressure release valve which dispells the excess pressure. On newer cars it's silenced but on after market and older turbos u hear a "pssssss" sound which is the excess pressure being let out, mainly when switching gears. happy turboing!