[brian015]

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Your answer is simple: it depends on how you gear it. If you gear both the 2200 and 2650 the same at 6s theoretically the 2650 would go faster - but you don't need to gear them the same - you could gear the 2200 higher because it is a lower kv and it is a bigger motor.

What will actually work without overheating??? That must be determined by trial and error. You can look at other people's setups and get an idea of what can be achieved.