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Old 02-11-2020, 02:15 AM   #1
Scooby Newbie
Member#: 511572
Join Date: Feb 2020
Default 2009 wrx making unknown noises

I just bought a modded 2009 wrx a couple days ago with 104xxx miles and have noticed a sound coming from the engine only noticeable from idle up to about 1500-2000 rpm. The sound speeds up as the engine does but doesn't get louder with the engine so it gets lost in the rest of the noise. I can barely hear it inside the cabin but i have to have the ac/heating fans tuned off to get it quiet enough in there to hear it. I can only really hear the ticking/knocking when i'm standing over the engine and really listening for it with the hood popped. i've driven it maybe less than 200 miles and it hasn't gotten any worse since I noticed it. It doesn't go away or get worse once the engine heats up.

obviously i'm hopping its not rod knock or a spun bearing or piston slap but those are the only things that come to mind.
it doesn't sound as rapid as valve clatter like i had in my last ej25

am i just being over protective of my "new" baby or is there really a cause for concern

does anyone have any other ideas or ways i can confirm/deny my suspicions?

list of mods to help the diagnosis:
blouch 380xt turbo
38mm wastegate dump
cnt downpipe
3" straight exhaust no muffler
cnt headers
Cobb sf intake
upgraded top mount
cobb 3 port boost controller
manely forged pistons
manely forged rods
new oem crank
king rod bearings
king main bearings
forge bov
tgv delete
stage 2 south bend clutch
act flywheel
new oem water pump
full timing belt kit
new power steering pump
mishimoto radiator & oil cooler
arp head studs
750cc injectors
cobb access port v2 with custom tune
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Old 02-11-2020, 06:29 PM   #2
Scooby Newbie
Member#: 511572
Join Date: Feb 2020

just spoke with a local "subaru expert" and had him listen to the car, his verdict was that its probably piston slap from the forged pistons not being the exact same tolerances as the original pistons and that its not really a concern because almost all aftermarket forged piston will have a little bit of slap. I hope hes right because i don't want to do an engine rebuild right after buying it lol
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Old 02-21-2020, 09:45 PM   #3
Scooby Newbie
Member#: 511572
Join Date: Feb 2020

while acquainting myself with the cobb access port that the previous owner installed in the car i came across the knock sensor readings for the individual cylinders. I went through them to see if one was significantly higher than the rest which i assume could tell me which cylinder has slapping issues (if the subaru expert is right) and i found that cylinders 1,2, & 3 are very low in their incidents of knock sensed, usually in the single digits where as cylinder 4 reached up to over 100 within an hour or so of driving.

It doesnt seem like it gets any better as it warms up but the sound seems to deaden a little bit but never fully goes away. should i get this fixed asap or ride it out and see if it really is just a side effect of having aftermarket forged pistons, it just seems like if it was, all the cylinders would have about the same knock readings. it seems like that much knock on cylinder 4 would cause damage but at the same time it hasnt gotten any worse since i got the car
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