Fenestrons need the most power. Up to 25%.
10-15% for a conventional "open" tail rotor is usual.
that the aircraft gained almost 25% more performance over an anti-torque tailrotor system.
Itīs on the first view correct to assume that without a tailrotor like the coaxials the ship will have a big power push. But in reality not so much as you think. At first is the lift production on the coaxial not the same like a single disc. (means factor 2 with the half diameter of the coaxial). Only round about 1,6 is to reach mainly due to aerodynamic losses and influences between the both rotor discs.
And at second is the weight of a technical coaxial construction much higher than of a single rotor with tail rotor. Thats why also a KA-32 needs really big engines. Coaxial is interesting, but itīs not a perfect solution.