Escaping/ Compressed Air Noise
 

Hey guys. I wanted to revisit this. I've been looking to figure this out for months now and haven't been able to find anything. Since about late October I've been hearing a noise like compressed or escaping air whenever I'm in motion. Also, when shifting above 3.5K RPM you can hear a blow off valve or release of air type noise. Funny, because the car is completely stock and has no turbo. I've checked the intake and even went as far as deleting the sound tube to see if it made a difference, and it did not. No exhaust leaks either..

Bad vacuum line, maybe? Maybe drivetrain related?

Auto?

MT. 13,700 miles on the odometer.

I hear it in my 2017 BRZ MT. It's totally stock.
I can only hear the noise when loading the engine, not at steady state.

I had my rear seats down and it sounds like it coming from the rear of the car, so I was thinking it was from the exhaust.

Try driving with your rear seats down and see if the noise is more pronounced.

Interesting. My noise is definitely coming from the front of the car. I hear it when it's steady and at WOT.

I hear the same noise from the front of the car, but I noticed it after I installed headers. It happens at WOT and when I rev it. I don't hear it at idle. I also have removed the sound generator tube. At first I thought it was a install problem with the headers and I had a leak, but after a rather lengthy inspection I couldn't find any exhaust leaks.

Do you happen to get a BOV noise when shifting around 3500-4000 RPM? Just curious..

If it were a vacuum leak, I would think the engine would tell you via a code.

I can't imagine the driveline making a sound like that .....:iono:

I might suggest you re-check the intake for a lose clamp, lose hose, split hose or something else wonky.

Maybe your NOS is leaking ......:D


humfrz

I have an air like sound under load but that’s because I have a leak between my header and over pipe. Took a while to isolate it but it looks as if the flange is bent a little. Spray it with soap and it bubbles on the bottom end of the flange and you can see a gap at the bottom of this flange.

I’ve never noticed a BOV sound on shifts. The only sound I’ve noticed on shifts was a little ingnition knock (sounded more like a click) when doing very quick shifts were I would go back to the throttle very quickly and aggressively. I wouldn’t describe the sound as a BOVish sound though. I solved this problem by taking the transient ignition retard table from the 2017 rom and applying it to my 2013 rom. The 2017 TIR table pulls a lot more timing on transients then past roms. The sound is gone now.

Sounds good. I’ll give that a check this weekend. @humfrz I’ll double check the clamps on the intake, maybe I overlooked it. :thumbsup:

Yeah, I don’t usually hear the knock these things have, I do know what you’re talking about though. It really is a head scratcher, though. It’s like compressed air being released when I shift above 3.5k. :iono:

No, I don't hear anything like a BOV. At this point, I have no idea what it could be.

Could also be the "whooshing" that happens with thinner wall headers.

I've noticed a similar sound when I installed my k n air filter

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I farted once when shifting.