Well...... I have to eat crow here....... I have said in the past it might be good to wrap the pipes.... One thing for sure is that it helps keep the under hood temps down. The reason I believed wrapping the pipes was good was because of the concept of the hotter the exhaust gas the faster it exits. Through more research the turbo car is more complex then just using this formula. The turbo works on 2 principles..... 1. pressure differential 2. heat differential. For the pressure difference you want high pressure before the turbo and low pressure after the turbo wheel. Similarly with the temperature you want as much heat before the turbo as possible and you want it cool after the turbo wheel to have the greatest efficiency. If you picture a exhaust vent turbine on top of a building......It spins like crazy even with no wind when there is heat in the attic because it is hot in the attic and the heat is looking for cool air outside and spins the turbine. So by wrapping the down pipe you are holding the heat in the down pipe causing a lessor heat differential and this probably is not the best :)
