A good light? .01X or better. A great light? .000X. However none of those will guarantee a win if the car is off the dial. I've lost with a .004 light and .006 off the dial. I've also won with a .168 light and shut the car off at 1000'. You have to be able to race the finish line as well as the starting line. Most times the finish line is more important than the starting line. I kept meticulous records on engine temp, oil pressure and weather and was usually able to dial my car to within .006. Of course that didn't happen overnight either. I also prefer to be the faster car as you have the whole race in front of you so I built my cars to run at the bottom of the class and slow it down if necessary.