Turbo wastegate rattle in your 2017 Subaru WRX creates an annoying rattling or clicking sound from the engine bay, particularly noticeable at idle or low RPM. This common complaint on the FA20DIT engine relates to the twin-scroll turbo's internal wastegate design.
Understanding WRX Wastegate Rattle
The WRX's twin-scroll turbo uses an internal wastegate—a flap valve that bypasses exhaust around the turbine to regulate boost. Play in the wastegate mechanism allows the flap to vibrate or rattle against its seat, particularly at low engine speeds where exhaust pulses are distinct.
Why Rattle Develops
The wastegate actuator arm and flap develop play over time from thermal cycling and exhaust gas exposure. The rod connecting the actuator to the flap wears at pivot points. Heat-related expansion differences between components create clearances that didn't exist when new.
Stock vs. Aftermarket Implications
Stock WRX owners commonly report wastegate rattle developing after 20,000-50,000 miles. Some aftermarket solutions like wastegate actuator brackets or adjustable actuators address play, though this may affect warranty coverage.
Performance Impact
Minor wastegate rattle is primarily an audible annoyance without significant performance impact. However, severe play can affect boost control accuracy, causing boost creep (uncontrolled boost increase) or inconsistent boost pressure.