Like all serpentine belt engines the Subaru benefits from under-driving the accessory pulleys to reduce parasitic power losses from the alternator, air conditioning, water pump and power steering at high engine RPMs. A smaller, lighter harmonic balancer also acts like a lightweight flywheel by sharpening throttle response and allowing the engine to rev out faster.
Powerbond have now released a 25% under drive billet steel balancer for the WRX that is SFI approved for all forms of motor sport. The precision CNC machined steel hub and inertia ring is assembled using Powerbond's pressure bonded rubber eliminating balancer separation and spinning. Every Powerbond unity is dynamically balanced at the factory for smooth running at ultra high RPMs.

Application: Subaru E16, E18 and E20 4 cylinder engines