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Old 10-14-2020, 10:25 AM   #1
Scooby Newbie
Member#: 498310
Join Date: Feb 2019
Default Engine noise. Rod knock..?

I have a 2004 STi with a built ej257 with Manley rods and pistons, bored to 100mm, 11mm oil pump, stock 2009 nitrided crank, fully built valve train. Turbo back exhaust, Rebuilt vf39 turbo, Perrin turbo inlet, short ram intake. Did a 2000 mile break in on the motor limited to 5psi and 5k rpm (Probably overkill but oh well). Switched to Cobb accessort stage 2 with 91pump gas (live in the Denver area), and everything was fine for about 1000 miles, now Iím hearing this raspy noise and not sure if itís knock or not. Itís only happening when under load about 3-4k rpm, and I donít hear it when I start going into boost and the AFR gets richer. Wondering if:
(a) it is knock or could be something else.
(b) If itís happening due to quality of fuel/fuel octane? Could fuel just be bad and timing is off in that area?
(c) Is 91 the right map for Denver area? Should I go to an 89 map?
(d) would a custom tune eliminate it?

Thanks in advance!
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