[othello]

As lincpimp pointed out: a smaller motor can achieve similar power levels then a bigger motor when you rev it higher. I started with a Neu 1512/2Y (1400kv) in my truggy which was geared 1:16,8 and it reached 38000rpm under load with 10s1p A123. I then replaced the Neu 1512 with a Neu 1515/2Y (1100kv) geared it 1:13 or 1:12,13 with the same batteries: the motor reached 30000-31000rpm under load. Both motors peaked at 2.5KW, top speed and temperatures of all components were similar. But the feel was different. The smaller Neu 1512 seemed more responsive, spun up faster and was easyer to drive, the Neu 1515 had crazy amount of torque and wheeled the car far more often as the smaller motor. Acceleration was almost identical with both motors as the chassis and tires were the limitation. Drive time was similar too.

Higher revving motors can become difficult to gear. 11 or 12 tooth pinion is the lowest you can go. You might need a bigger spur (truggy). By choosing a higher kv 1509 gearing becomes even more crucial as lower turn motors need higher Amps to achieve the same torque level as higher turn motors. I would crunch some numbers using the very handy speed calculator and look if you can gear a high kv 1509 properly. You may also drop Mike @Rcmonster a mail and discuss which 1509 would be best suited for 4s and which gearing he would recommend.