Guys, First of all, I'm new to modding of power wheels but not to speed and racing. I've read over the FAQ's and haven't seen an answer to my questions. First what is the differnece between a 21 turn motor and a 23 turn motor. Second how many rpms do the titan 550's 21 turn. I plan on using them on my lttle girls barbie jeep. What pinion do I need if she has a 19t gear box. I plan on stepping up to 18 or 24 volts and using heatsinks with fans. Any advice would be great and answers.