My MMX ESC handled the C1515 (40x75, 150A) just fine for speed runs and I hit 94 mph with it in my 1/8 truggy, but it did have some weird "motor start failure" errors. However, it did NOT like the TP4070 (40x102, 200-350A) which is a lot bigger motor and pulls a lot more current. It was pathetically slow and worthless. It felt like a brushed Summit. This is dissapointing and it seems Castle has put a very strong current limiter or something on their new ESC's and it just kills ALL of the power. I just put in the XL2 and it is an absolute beast.