The 8 wrap coil is used mostly when doing an outline with a 1,3,4, and a 5 needle outliner. I would not recommend using an 8 wrap coil outliner machine when doing larger outline work such as when a 8 or 14 needle outline is called for. You would have to increase the voltage (by turning the power supply up) which would cause the machine to heat up and lose power.
This would make the tattoo machine run hotter and even possibly cause the machine timing to break up and cause an uneven outline.
When you are going to use a 8 or 14 needle outliner, I would recommend using a 10+ wrap coil tattoo machine.