easy adjustments Dual ball bearing-supported crankshaft extends engine life and improves reliability Overview The Evolution® .61NX will be replacing the popular .61NT engine. This redesigned engine incorporates a new combustion chamber design that increases the compression and power of the engine. Its improved combustion chamber design and higher compression ratio result in more power at the same weight as the original. Along with the internal engineering updates, the .61NX sports a sleek external case. With improved performance and looks, the .61NX will be a great option for modelers looking to power their .60-size airplanes.