These two odd looking gears will spring together in a 3:5 Ratio. The gears were printed on a dual nozzle printed with water soluble support material.  I would recommend printing them vertical if possible.  
Its interesting to see the different speeds of the gears and watch them mesh as they don't appear as they should be able to.  
In real life the gears would spin so fast that they will pump and compress air. This forces air into the intake of a vehicle, increasing its power.  
http://www.youtube.com/watch?v=SyElxCYI4As  
Note:The model shown in the picture is a bit different, because I later improved the model design to upload here, but was rushed to finish for a class for our actual model. The case was not 3D printed, that is why It looks terrible.