Hippo Machine
Because Wet Leaves
I don't know if this sound is normal when revving the engine, take a look:
http://s1096.photobucket.com/albums...on=view¤t=video-2011-12-22-15-43-27.mp4
http://s1096.photobucket.com/albums...on=view¤t=video-2011-12-22-15-43-27.mp4