So my stage 2 GTS with BMC filters has been sounding like making a strange vacuum sound when the turbos are engaged. I've heard it before but never this loud. I noticed the sound much more after having my coil over kit installed. Can anyone with BMC filters confirm if theses normal? If you listen closely you hear it over the exhaust.

 

Not seeing a video.

If the only thing that was done between this problem not happening and this problem happening was suspension, the low pressure side of one or both of the turbos might have been knocked loose.

 

Okay, with video there, that sounds like a boost leak. Do you feel down on power?

 

Wouldn’t that trigger a CEL?

 

yes

 

Is that something I can check at home? My car sits on a lift so easy access to the underside.

 

Yeah, I'd expect a CEL for a serious boost leak. A smol one though, maybe not? Depends on Porsche's parameters.

If the car's under warranty, just take it in.

Otherwise, yeah you're in for some fun. Most of the charge piping is behind the rear bumper. The U-shaped pipe you can see in the wheel well is the low pressure side of the turbine (which will also create such noises if it's loose). You should be able to pressurize the system there to check for a boost leak -- quick googling doesn't come up with any how-tos for checking boost leaks on 991s though.

 

To install the suspension, the turbo inlet and outlet pipes are right there. So they likely got moved/bumped, or uninstalled/reinstalled improperly.

 

are you referring to the black U shaped hard plastic pipe?

 

That’s a boost leak. It does not necessarily throw a check engine light.

 

The black U-shaped pipe is the compressor inlet pipe, which gets air from the air filter. The other pipe leaving the turbo is the compressor outlet pipe and that is the high pressure pipe which goes to the intercoolers.

 

Worth noting that either one being loose will cause a much louder spooling sound, but the charge pipe (high pressure, intercooler side) being loose will lead to slower spool and outright loss of power.

 

What does your boost guage read? When I had a boost leak I didn’t get a check engine light but I could only generate max of 13 psi boost and my GTS should be at 18psi.

 

What caused your boost leak?

 

I had something like this happen on my 991.2 GTS - it appeared to come from the left hand side of the car (passengers side here in the UK). I'd taken it in for a service and noticed it soon after I got the car back. It only occurred under hard acceleration. I took it back in and the mechanics thought they'd just not tightened things up correctly but the problem persisted. Anyway, at the second visit they discovered a small rupture in one of the pipes which opened up under the hard acceleration causing the sucking sound whilst on the gas pedal. All replaced under warranty and fine since - it might be worth investigating this as a possible cause, it must have happened by accident during the service.