Ok, so you are a 3D printer person, but also a car nut. How to "hot rod" that printer? Why, add a velocity stack to the cooling fan of course! This has no real need, but should increase fan flow by 5%ish. I made just because it looks cool :) Shown here on my Printrbot, but should work with any same sized fan with a clear path to it. I included a second version with a full radius bell and a center flow deflector to keep the air moving over only the fan blades. This one will also print with no supports "Bell up" if you get all your settings right. I had a few stringers on the backside, but still happy with the print. I print with 10% fill at 15mm/sec in PLA Its a bit tricky to print. I printed "bell down". Left a few fuzzies at the screw mounts, but just filed the fluff off. Printing Bell up, needs lots of supports, with not as nice a bell, but makes for a better base