Pssh Sound When Decelerating
 

I noticed that I hear a faint "pssh" sound when decelerating. It's very faint, as my husband can hardly hear it, although now I can't stop hearing it! I notice it mostly when I let off the gas, or shortly after downshifting at lower gears. Does anyone else hear this noise? I used to have a turbocharged Audi, but never had a car with a supercharger. I'm just wondering if this is a normal sound, or something that I should ask the dealership to look into.

Someone recently posted about a sound that sounded like something was sliding under the floors on decelleration. Superchargers don't need pooosssssshy blowoff valves like turbos, because they are physically attached to the crankshaft therefore boost naturally follows throttle input.

No, it's definitely not a sliding sound. It sounds like air being released from somewhere on the left side of the car.

Thats really weird. The only thing I can think of is maybe a leak in the driver's side vacuum line to the loud/quiet muffler valve? The strength of the vacuum could be tied to engine RPM

Do both sets of dual exhausts match in loudness when you change from loud to quiet mode? If there is a vacuum leak on the drivers side, the dual exhausts on that side might stay in loud mode regardless if the switch is set to quiet.

It's possible it makes the sound more than you think, but when you're on the gas it's completely drowned out. Are you sure it only appears on decel? Does it change relative to vehicle speed?

I haven't noticed that. It sounds pretty balanced to me.

It could definitely be drowned out at higher speeds. I'm pretty sure it's at decel though. It's definitely not constant, and when I do hear it, it's usually just after I've let off the gas, or when it downshifts. It otherwise drives fine, handles great, it's just a bit of an odd sound. I'll have the dealer look at it when I take it in for inspection. I just figured they wouldn't be able to hear it, plus they will want to keep it for weeks while they're trying to figure it out. I actually didn't notice it until I brought it home from the dealer after getting the annual service done, new tires, and alignment.

It might be a heat shield rubbing against a rotating part (e.g. driveshaft, halfshaft). Those shift a little from accel to decel. The more specific you can describe the conditions when it manifests the better chance you'll have on getting it resolved quickly. Speed, throttle, what you were doing before, straight, curved, etc.

I was initially thinking it might be a brake shield rubbing on a rotor. That's still a possibility although that's usually not a continuous sound, but one that varies by vehicle speed.

can you get a video?

I didn’t know it was possible to hear anything on decel with these cars except for the overrun soundtrack.

I can try, but I'm not sure if it would pick that sound up.

Lol! This is at low RPMs.
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OK, not just at decel. I also heard it today after starting the car. After 30 seconds or so, the exhaust quieted and I heard that air release sound again. I was sitting in park the whole time. I think it's the valve closing, so maybe @RacerX is right. I'm hoping it's OK to keep driving until I can get it in for inspection, which at this point, won't be until the tag places and other businesses open back up.