Ringland failure in the 2015 Subaru WRX's FA20DIT engine is a serious concern for enthusiasts, though the FA20 is generally considered more reliable than the previous EJ257 in this regard. Understanding symptoms enables early detection before catastrophic damage occurs.
What Is Ringland Failure
The ringland is the section of piston between ring grooves. Under extreme conditions, this thin section can crack or break, allowing combustion pressure and oil to bypass the rings. This causes immediate compression loss and often rapid engine damage.
FA20 vs. EJ257 Considerations
The FA20DIT engine uses stronger piston construction than the EJ257 it replaced, reducing (but not eliminating) ringland failure risk. The direct injection system also provides better fuel distribution, helping prevent detonation-related failures.
Warning Symptoms
Early signs include increased oil consumption, rough idle that develops suddenly, compression loss on one cylinder, blue smoke during hard acceleration, and knock sounds under load. These symptoms warrant immediate investigation.
Contributing Factors
Aggressive tuning with improper fuel or timing causes detonation that stresses ringlands. Running lean under boost creates dangerous temperatures. Low-quality fuel under heavy load risks detonation. Stock vehicles occasionally fail from manufacturing defects or abuse.