My thoughts are, on the SP device is just the same as the MM Motor Dyno, or any no load motor checker. You buy a motor, spin it up, run it on the track and after you own it and it starts to feel bad, spin it up and see how the performance is again. Any motor Dyno is a guide, not law. Even when I had a Fantom dyno, and chopped springs, switched brushes, stroked it nicely and played with the bushings, a crap motor is a crap motor. You are only using it to find out what numbers makes a good motor, and to verify consistant performance. The best part to me is, is if I have a good motor I know how it performs on the dyno and track, then when I am thinking it is garbage I can verify that fact.
Speed Passion U.S.A. - Turtlemaster Racing