Results happen fast after installing a GFB water pump pulley. Switching out one part for another can make a big difference, especially if the part being replaced is big and heavy. The key for turbocharged vehicles is using lightweight components to maximize power potential. That is what this particular part is best for. It weighs approximately half as much as an OEM pulley but is just as durable. Once in place, the benefits are discernible immediately. You will notice cleaner shifts and more consistent acceleration. That’s why most performance drivers look at a Go Fast Bits water pump pulley as a step towards a complete turbo engine package.
The main aspect to this upgrade is the weight. Go Fast Bits constructs all of their lightweight pulleys out of T6 aluminum. This material is used in favor of a heavier substance such as steel or iron. All told, the part weighs about half a pound. It is also (slightly) underdriven, which means it rotates at a lower rate than the original factory part, drawing less power. It also uses less rotational mass, which helps some extra power become available for acceleration. This does not result in much higher speeds necessarily, but instead, smoother revs. Once in place, gear shifting is a whole lot smoother.
That is the main area of confusion. Switching in an aluminum pulley does not create more horsepower. What it does help with is catching gears, especially in a lower range. Since it is drawing less power, RPMs do not have to flatline when coming down in shifts. Going from 3rd to 1st no longer means a precipitous drop. The Go Fast pump pulley helps gears catch quicker so you do not decelerate by a large margin. In an FR-S or BRZ, this can be a big deal. Revs maintain a consistent level, even when going from gear to gear. Your car runs more balanced after an aluminum water pump pulley is installed.
This is not a universal part. Replacement kits are available for the Subaru BRZ and Sicon FR-S. Installation involves removal of the original part and may vary in difficulty depending on surround components. All pulleys come with complete instructions.