There is one "economy" (there, I said it without saying 'ghetto' - - hah!) way to do this:

Know how long your allen wrench is. Like if you have a long-handle set with the ball-end on the long end.

Attach a fisherman's scale ($4 from a sporting goods store) to the end of you allen wrench and pull to the correct poundage.



So if the torque spec for your supercharger is 4.8 nm (if it's something else, there's a nm to inch-pound converter here), that's about 43 inch-pounds. If the 'pull spot' on your allen wrench is 5" from the bolt center, you'll need to exert 43 ÷ 5 = 8 - 9 lb.s pull on the end of your wrench. Easy.