I came across a post a few nights ago that made me finally decide to ask. @Dazmlp66
was experiencing the same noise in these posts:
Hi Guys and Girls , I have a growling noise on my 2020 WRX STi which has been bugging me since I got the car new. It starts around 2500 rpm to 3000 rpm you can just hear it when you are driving when the clutch is pressed to change gear. But you can also hear it when you are stationary see video...
Clutch noise at 2500 rpm ?? Transmission (AT/MT) & Driveline
I sent @Dazmlp66
a PM, but have not heard back.
I have a 2021 STI, 6k miles, Group N trans/engine mounts, Whiteline shifter bushings and rear diff inserts. All stock for power. I have had my car to the dealer twice now to investigate this noise. First time they were unable to replicate. When I finally figured out how to replicate it reliably, I grabbed a video and took it back. They heard it and could replicate, but claimed that another STI made the exact same noise and chalked it up to resonance/"it's normal".
I've done two UOA's now... metals are normal, and trending down. Noise has been around for about 4000 miles now. No specific mod has made any change, and it didn't start happening around the installation of anything.
The second video
captures it the best. It's right upon rolling into/stabbing the throttle that there is a rattle that tracks with engine RPM. I'd post my video, but it is literally identical to this. This [noise on throttle stabs/RPM accel] initially made me paranoid that it was rod knock. My s2000 developed rod knock at a track day. But, the fact that this has been going on for months and 2000 miles really makes me doubt it is, along with two good UOA's. This also does not present at all under load, only free revving, or sometimes right between maintenance throttle and decel. IME rod knock gets worse rather quickly, esp if you run the car hard, and gets really loud if you put the car under load. It also doesn't happen with the clutch out when revving, but does when I press the clutch in.
So... anyone have any guesses or ideas on wtf it is? I lean towards clutch related since I can manipulate it with that, but I'd think clutch related stuff would make noise with the clutch out... Pilot bearing related?
Thanks for reading if you read it all! Hope to get some insight on it.