Ok so this is untested but im working on it and should have the results within a day or so but here is is. Also please note i got the idea from XMW and just altered it to my need.
Here's the "Blue-Print"
The idea is the air flows thur the hood or roof scoop which ever you decide to use and travels thur the straw into the motor can out the other end thur the straw and out your custom exhaust tip idea being it forces the hot air out the can and out the exhaust also since the arm. inside the can is spinning it would force the air out creating back pressure? Well let me know what you guys think and ill let you know the results once i complete it.