Subaru turbo drivers will install a Perrin EJ pulley when they are looking for better timing results. The factory part is not designed for the kind of performance you are interested. It is heavy, cumbersome, and contributes boosting issues. The Perrin EJ pulley is engineered to present a lighter weight answer that demonstrates an improvement in shifting and overall response. This is not a customization exclusive to racers and tuners. Residential motorists benefit, as well. Less idling at traffic signals along with a reduction in noise make Perrin EJ pulleys a suitable alternative for all Impreza and Forester owners.
Its lack of weight is the most telling attribute. Perrin crank pulleys weigh 1.2 lbs, making it among the lightest in the industry. By comparison, the stock unit comes in at 3.5 lbs. The advantage a light Perrin crank pulley offers is an ability to withstand stress coming off of the associated parts (alternator, A/C, pump, etc.). Its lower rotational mass is not as vulnerable to resistance. Perrin crank pulleys are able to display freer movement. This improvement in motion is how you are able to notice the benefits when the car is in motion. But that is not all it offers. Perrin crank pulleys also make shifting easier.
One of the biggest gripes Subaru turbo enthusiasts have is that there is a “pause” going between gears. This holds back acceleration. A lightweight EJ crank pulley helps the engine kick into revs much faster. There is little to no hesitation. Since there is less rotational interference, accelerating is not compromised. You may also notice that when stuck in traffic that there is a decrease in both steering wheel shakes and noise. That is evidence of the lightweight EJ crank pulley not hitting forcible rotation. Instead, it spins without restriction. This also assists with constant shifting. A lightweight EJ crank pulley makes getting back up to speed quicker than before.
A critical element is the material. It has to be both light and extremely durable. Perrin WRX/STI pulleys are made of 6061 T-6 billet aluminum. The grooves are machined in via CNC, making the unit applicable with most aftermarket belts. Finishes include red and black. Choose a contrasting look or try to match your other EJ series engine parts.