XT 2.0 Turbo (FA20DIT) knocks at high RPM wide-open throttle

whobodym

This summer on two trips on high-speed 2-lane roads, my Forester XT has given a startling burst of what sounds like ignition knocking, immediately after applying wide-open throttle and the CVT downshifting at highway speeds for a passing maneuver. It doesn't occur in any other driving situation as far as I've noticed, and it didn't occur during the winter or springtime. Is this normal and harmless? Carter Subaru of Seattle seems to say so. I do use premium fuel as recommended. I would expect a car with a knock sensor like this, to perform more sluggishly but not knock, if fuel were the issue. Advice / comments please...

saedave

Is your fuel 91 octane or 93 octane? M7 2014 XT has no problems on 93. There was a recall some time ago; after the recall mine seemed to have reduced fuel economy. Was yours recalled?

whobodym

the August post above was a total blind alley. my car's problem was an exhaust leak, not knocking. the dealer said a nut had backed off the RH exhaust manifold and then the gasket failed enough to leak at high boost/rpm. oddly it was me myself first suggesting an exhaust leak to them -- but not at the cylinder head. I thought the leak might be as pictured here downstream of the turbocharger. the mechanics wire-brushed this pictured location and concluded it is normal and not leaking.

I'm very interested to find out if other FA20 DIT engines have exhaust flanges that look as ugly as mine. Anyone?