I have used a tach for getting the length of a tuned pipe right, and for some of my racing birds, but for the normal joe flyer, both the tach and the heat sensor are toys. Both a waste of money as far as I am concerned. You will use it once and then it will sit in the flight box and rot. Do as MNF says. Use the recommended procedures and don't waste your money. If you need to tach it, borrow one from someone that got one. He will be more than happy to get some use out of it.