This is a class action on behalf of owners of 2009-2014 Impreza WRX vehicles (“class vehivcles.” Subaru introduced the class engines in the United States market in late 2007 for the 2008 model year. Class engines are predisposed to premature engine failure. Class vehicles are defective with respect to improperly designed and manufactured pistons and an engine management system and PCV (positive crankcase ventilation) system that subjects class engines engine to premature catastrophic engine piston ringlands failure (the “Piston Ringlands Defect”).
WRX and WRX STi engines are high performance versions of the 2.5 liter displacement EJ series engines used in other model Subaru vehicles including but not limited to the Forrester, Legacy and Outback. These performance modifications nearly doubled the horsepower for WRX and WRX STi engines over the standard base 2.5 liter engine. These performance modifications that created substantially increased power output did not include necessary internal engine modifications to prevent damage to the piston ringlands.
Inadequate class engine piston ringland durability was caused by casting the class engine pistons from hypereutectic aluminum silicon (Al-Si) alloy. While this alloy has some strength attributes over conventional cast aluminum pistons, Al-Si pistons and in particular piston ringland are more brittle. This Al-Si materials selection and cast construction method resulted in insufficient strength pistons in class engines.
Another contributing cause to class engine failure was an inadequate PCV system that allowed excessive engine crankcase oil vapors to be introduced into the engine combustion chambers thereby lowering the overall fuel/air octane mixture. This causes increased combustion forces acting on the piston through a phenomenon know as detonation. Detonation is a well-known cause of internal engine component damage particularly including piston and piston ringland failure.
Failure of class engines due to the Piston Ringland Defect results in sudden power loss and/or stalling that severely compromises the owner’s ability to maintain vehicle control. The defective class engine components and engine management system also causes sudden an catastrophic engine self-destruction as overheated internal parts seize.
The failures in the class engines due to the Piston Ringland Defect pose a serious safety issue while the vehicle is being operated since there is loss of engine power without warning and the loss of power-assisted steering and reduced braking caused by lack of engine vacuum if the engine stalls. In class vehicles equipped with manual transmissions, the drive wheels will lock and cause loss of directional stability and steering if the engine stalls and the clutch is not immediately disengaged.