By using Forged Billet aluminium machined on a 5-Axis mill, the Billet Compressor wheel can be designed much more aggressively, the nose and hub can be designed significantly smaller to allow for a greater blade diameter
The blades can be made much more complicated to increase blade surface area, which flows more air into the engine
By using Forged Billet aluminium, the wheel can be machined much thinner and lighter. This allows the wheel to have a greater efficiency range, because there is less blade thickness to contact the air and heat it up.
It also means that with less blade thickness and lower hub area that there is a greater area between the blades to squeeze more air and build boost pressure
The more efficient a wheel is the lower the intake temps, and everyone knows the cooler the air going into the engine the more horsepower you can make!