title_body: Does motor KV requirement scale linearly with voltage? There have been myriad questions regarding motor KV, such as this one. Many of these come close to answering my question, however none have given me a definite answer.
  
  If I am picking motors for a build, will the motor KV required scale linearly with voltage?
  
  For example, if I know that for a 3” build on 3S (11.1V) I will need 3000KV motors, to find the required KV for similar motors to spin the same propeller on 2S, would I multiply the KV by 3/2, giving me a KV if 4500? If so, does this hold true for larger motors as well?
upvoted_answer: Assuming all other variables stay the same, yes, The Kv should scale with voltage completely linearly. There are some other changes in the electrical system due to the voltage change that have some impact on efficiency, but when Kv is changed along side voltage, that is largely mitigated. Based on the tests we've run and comparing the resulting data on the Mini Quad Test Bench motor explorer efficiency is usually within a couple percent if you scale Kv properly. If you got to crazy extremes you might see a bit more variation, but I don't have data at those extremes. For most practical applications you can assume a linear relationship.