The deltajet-400 with the stock sp400 is 12 amps (about 120 watts) on a 3S 2100 thunder power pack. I recommend a B20 22L which only draws 9 amps (90 watts) but is a nice boost in power compared to the brushed speed400 and gives very long flights. The B20 18L gives more power at 14 amps and about 140~150 watts and would be the max I can officially recommend. Not quite unlimited vertical but really fun. I fly a B50 15L, which is 23 to 25 amps depending on which pack I use (I have various 3S 2100 packs that have been abused to varying degrees hence the difference
, but the 15L is above both the battery and motor specs and although I have had no problems, it's pushing things really hard. That's the setup I was flying at SEFF last year that would SOG (slide off ground
) and has unlimited vertical.