"The turbine wheel is responsible for converting heat and pressure into rotational force. Turbine Wheel material,K418 made by Forging
Turbine Shaft material, 42 CrMo made by Forging
The turbine wheel converts kinetic energy into rotation. As the turbine wheel rotates, it spins the turbine shaft, which in turn spins the compressor wheel. Often overlooked, turbine wheel selection is critical to a properly built turbocharger system, as having too small of a turbine wheel will induce excessive backpressure and can choke the engine, making it lose power. On the other hand, selecting too large of a turbine will result in increased lag and can make it difficult to achieve specific target boost numbers."