put a tekin 4.5 sc4x in yesturday and run on a indoor clay track and think i'm actually slower then when I had a lrp 6.5 540 in it lol. The 4.5 is to torquey all the throttle is right in the beginning where as the 6.5 is way smoother and the power is more on the top so you can work the throttle better no so on/off. I think i'm gonna switch it back before the race tomorrow.