I've got one of these: http://www.harborfre...ator-97762.html mounted in the wall right below my reel grinder. I put it in mainly to pull the dust out of the shop while grinding but i also use it for exhaust fumes as well.
I attach the flexible vent duct: http://www.harborfre...duct-97763.html to the fan and put it in front of the exhaust on the machine I'm running. Usually just set the vent duct up on a jack stand a few inches away from the muffler or tail pipe and tie it in place. Works like a charm.
Kinda hard to see the fan in the pic but it worked very well on the machine I have in the shop right now. Owner pulled the injection pump apart and it has only been running on one or two cylinders ever since. Mosquito control at its finest.