Lighter means better when it comes to GFB alternator pulleys.
Heavy stock engine parts slow things down. Drivers notice this during crucial situations, most specifically when shifting. The slightest hesitation can be responsible for the loss of precious revs. A GFB alternator pulley helps speed up shifts so there is no hitch point when hitting lower gears. A main point in this operation is the difference in weight. OEM Subaru pulleys are hefty and cumbersome. They draw more power due to their size. The part also employs less rotational mass, spinning just a little slower so that your throttle response is markedly improved.
If you are accustomed to climbing up in gears to max out HP, you may not see a huge difference. But that is not what this pulley kit is designed for. Instead, the intent is to make cruising at lower gears more responsive. There is often a deviation in boost when coming down in gear with the stock setup. Installing a Subaru alternator pulley kit keeps revs consistent in lower gears so that RPMs do not hit a snag. Going from 4th to 3rd or 3rd to 1st no longer represents a space of lag. There is more punch available since less energy is taken up, allowing for optimal rotation.
Turbocharged cars need balance in order to function. If you have installed car performance accessories, a WRX STI alternator pulley brings it all together. Parts such as a short shift kit work even better combined with the quickness GFB offers. WRX STI alternator pulleys allow for consistent acceleration going into gear. The result is not going to be a massive increase in horsepower. However, the WRX STI pulley allows for more horsepower to be available to other parts. That is because less charge is being drawn. The decrease in rotational mass is directly responsible. Plus, despite being underdriven, it will not adversely affect electrical components if installed correctly.
Material is an important part of the equation. Each lightweight pulley is made of T6 billet aluminum that aids in its composition. This type of aluminum is not only light, but extremely durable, as well. Impreza pulley kits are given a sleek black anodized finish that protects against heat and corrosion.