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Subaru of America announced a service campaign this week focused on the 305-hp turbocharged 2.5-liter four powering the 2008 WRX STI. According to the verbiage on a letter sent to an owner, Subaru states that "abnormal combustion" could occur when the engine is repeatedly or continuously operated above redline (6,700 rpm). At these high engine speeds, the Engine Control Module cuts fuel to the powerplant to protect the engine from even higher revolutions (this is common industry-wide, not just with Subaru). Unfortunately, under certain situations the Subaru 4-cylinder Boxer is still under high boost and the fuel cut-off causes the engine to run "over lean" resulting in combustion that breaks piston ring lands... eventually destroying the engine.
Subaru's "Service Program Campaign WVE15" reprograms the Engine Control Module software to improve combustion at engine speeds above redline, preventing engine damage. Subaru is quick to point out that the revised programming "will not adversely affect the peak performance" of the vehicle, so owners need not worry about the free campaign messing up their 0-60 sprints. Letters from Subaru will go out to owners in the next week or two. In the meantime, try keeping the white needles out of the red zone!
Related GalleryReview: 2008 Subaru Impreza WRX STI
Dear 2008 WRX STI owner:
During a quality review, we discovered that under certain harsh driving patterns, specifically when repeatedly or continuously operating the engine above the "red-line" (RPM above 6,700), abnormal combustion could occur resulting in serious internal engine damage in the form of broken piston ring lands. This abnormal combustion condition is the result of an "over lean" fuel mixture caused by a combination of fuel cut activation and high turbo boost. To prevent this condition from occurring, Subaru has developed a modification to the Engine Control Module software logic that will improve combustion management above "red-line" engine speed. This revised logic will not adversely affect the peak performance of your vehicle.
Thank you for the opportunity to be of assistance. If you need any future assistance, please let us know.
Subaru of America, Inc.
Customer/Dealer Services Department