Harmonica sound when on boost

[Kaldek]

Hi folks,

My 2000 model will get a custom tune shortly-ish but in the meantime I've been tweaking the boost controller just to get a feel for how these things work. It's an APEXi AVC-R unit.

Anyway, with a setting of 12psi target boost and 55% duty cycle (no gear learn or anything yet), the car peaks up to about 15psi and when it does I can hear a faint harmonica sound from the engine bay. At first I thought it was some kind of boost alarm but none of the stuff in the car has that function. The sound only occurs at boost over ~12psi I'd say, and I'm thinking it's a boost leak through a small orifice - ergo the harmonica sound.

I don't have a video of the sound yet but I'll make one. In the meantime, hit me with your ideas.

Stuff that may be of interest:

• The car will hold boost and the power is mental
• Boost comes on at around ~3,000rpm I'd say, but I could be wrong.
• I believe I have never hit boost cut as I've never felt any kind of loss of power when accelerating
• If I bypass the boost controller (i.e. setting 'OFF') it will reach and hold wastegate pressure
• I do not get the harmonica sound at 10psi or lower
• Drivetrain mods are:
  • Boost controller (duh)
  • Larger intercooler from Autobahn88
  • Custom 3" exhaust with cat

 

[whats_doing]

Has some silly bastard installed a harmonica?

Also, you would know if you hit boost cut. Your head would be violently thrown towards the steering wheel.

Most likely a boost leak. Get a boost leak tester to source it.

I will say mine used to do a whine sound whenever I spooled up (regardless of boost) and it turned out to be the rear turbo impeller rubbing on the housing.

 

[mookers]

I reckon you should add more harmonicas and figure out how to play tunes with your right foot

 

[Kaldek]

I like the videos where guys fit duck calls to their vented BOVs. Hilarious!

 

[NuffNuff]

mine did this, it was a hose clamp on the hot side of the front mount, wasn't quite sitting straight (was done up tight, but didnt seal very well) undo a few clamps and straighten them up and tighten nicely and take it for a spin

 

[Kaldek]

mine did this, it was a hose clamp on the hot side of the front mount, wasn't quite sitting straight (was done up tight, but didnt seal very well) undo a few clamps and straighten them up and tighten nicely and take it for a spin

Sounds likely. I had this pipe off to work on the clutch, so I've probably just been a nuffy and not put it back properly.

 

[TME_Steve]

Boost leak

 

[Kaldek]

Found the main source of the leak - missing hose clamp on the hose between the BOV and the high pressure pipe. Fixed that, now I still have a smaller harmonica playing somewhere else in the engine bay.

Reckon I'll figure that out shortly.

 

[Kaldek]

OK it seems that the ultimate source of noise traces to the boost controller sensor. I think I'll just remove this as I'm getting a TME tune in November. Can anyone upload again an accurate stock boost/vac hose diagram? I'm mainly concerned with getting the FPR and stock boost controller hoses connected to the right part of the intake ducting.

 

[VOLK]

http://www.ozvr4.com/threads/how-to-fit-a-3-port-boost-control-solenoid.12042/#post-288367

 

[Kaldek]

Thanks mate, much appreciated.

 

[Kaldek]

Righto, I've taken the car back to stock boost control. All the Apexi AVC-R shit has been removed and the stock hose routing is in place.

I have to say, these cars pull pretty hard from stock (well, if you count that I have a 3" exhaust). It's also pulling a lot cleaner than when the AVC-R was fitted, and there is no more harmonicas in my engine bay. I drove the car down to Phillip Island and back today, and my brother in law said that what I called a Harmonica he reckons sounded more like a guy playing music on a gum leaf.

Whatever you'd call it, the sound is most definitely gone.

 

[Kaldek]

Well a drive down to the MotoGP using stock boost shows that the factory tune is very drivable and really works nice. Looking forward to the quality high power tune from Steve even more now!

 

[Kaldek]

For closure, all boost leaks are gone and the car is running about 15-16psi with a tune from Steve. Currently about 160kw or so at the wheels with restriction from my exhaust and intercooler.

In the end I just checked all vac hoses and replaced any that looked suspicious as well. I also built a boost leak tester out of plumbing bits and used it to find and fix some more leaks that were basically solved by tightening the clamps on the high pressure pipes.

 

[DriftspecMC]

Had same problem. Check your one way check valve for your brake booster.

 

[pretzil]

I have found that intercooler pipes with loose clamps make a harmonica sound for me