Whistle under part throttle while coasting
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    1. #1
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      Whistle under part throttle while coasting

      Hi all,

      Does anyone else notice a slight whistle while coasting 30-40 mph under very light throttle (mostly noticeable from 2000 to 2500RPM)? Once I push the throttle more it goes away.

      I did a check of the PCV and it does not have the symptoms of going bad (suction from the dip stick or oil cap).

      I recently tuned the car adding an upgared downpipe, intercooler and custom tune. I do not notice a loss of power.

      It's an 2014 XC60 T6 with the 6-in line engine.

      I am assuming that it is a leak in the intake system or in the exhaust (turbo to downpipe), but perhaps it's a common sound and nothing to worry about.

      I am posting my query here as there is more traction in this forum than in the XC60 forum.

      Cheers,

      Bas
      2014 Volvo XC60 T6 AWD R-design: Ferrita DP, DO88 FMIC, Fasttech custom tune, BRC Sequential LPG system, Eibach Pro rear spacers, Powerflex torque rod insert

      2007 Volvo V50 T5 AWD M66 (SOLD)

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    3. #2
      Junior Member chrisz's Avatar
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      Oil separator likely.

    4. #3
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      When I did maintenance on the crankcase ventilation system on my 2005 S60, 2.5T, a few months ago, I found several hose connections that were loose. I guess that the synthetic rubber hoses can shrink over time, and they no longer seal well to the hose barb. This can happen even with a hose clamp in place. The solution is to replace hoses as necessary, with new clamps as needed. There is plenty of heat generated under the hood, and it will affect rubber parts, over time.

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    6. #4
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      Quote Originally Posted by hulsenbeek View Post

      I recently tuned the car adding an upgared downpipe, intercooler and custom tune. I do not notice a loss of power.
      Hard to say without hearing it first hand.

      It is most likely just the turbo beginning to spool. Would be much more noticeable with a tune and the hardware upgrades you did. The conditions under which you say it happens are perfectly in line with this theory. Turbo begins to spool around the low 2000 rpm range, and with part throttle (close to atmospheric pressure in intake plenum) there is sufficient exhaust gas to spool the turbo, but since you are not requesting the boost with your right foot, the diverter valve is being held open to prevent boost build up. Under those conditions the turbo is moving more air than the engine is requesting so some of the air is bled off back into the intake (pre-compressor).

      Tuned turbo cars whistle, it is a glorious noise, embrace it.
      Last edited by budleach; 06-25-2020 at 12:21 PM.

    7. #5
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      Best answer ever: Tuned turbo cars whistle, it is a glorious noise, embrace it.



      Quote Originally Posted by budleach View Post
      Hard to say without hearing it first hand.

      It is most likely just the turbo beginning to spool. Would be much more noticeable with a tune and the hardware upgrades you did. The conditions under which you say it happens are perfectly in line with this theory. Turbo begins to spool around the low 2000 rpm range, and with part throttle (close to atmospheric pressure in intake plenum) there is sufficient exhaust gas to spool the turbo, but since you are not requesting the boost with your right foot, the diverter valve is being held open to prevent boost build up. Under those conditions the turbo is moving more air than the engine is requesting so some of the air is bled off back into the intake (pre-compressor).

      Tuned turbo cars whistle, it is a glorious noise, embrace it.

    8. #6
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      Thanks for the analysis budleach. I do still have some concern though.

      I drove the car for a while yesterday and I managed to get the symptoms even more specific. The whistle sounds more like someone blowing on the top of a beer bottle than a high pitch whistle that I knew from my modded V50 T5 turbo whistle. The whistle starts around 1500RPM (instead of 2000RPM). With the V50, the high pitch whistle started at 200RPM and held longer trough the RPM range.

      I do not know if the turbo architecture is different, but I assume it is based on the difference between the XC60 and V50 turbo and mods available.

      I will check if I can find video's with the sound of the diverter valve to check.
      2014 Volvo XC60 T6 AWD R-design: Ferrita DP, DO88 FMIC, Fasttech custom tune, BRC Sequential LPG system, Eibach Pro rear spacers, Powerflex torque rod insert

      2007 Volvo V50 T5 AWD M66 (SOLD)

    9. #7
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      Quote Originally Posted by Eric T Johnson View Post
      When I did maintenance on the crankcase ventilation system on my 2005 S60, 2.5T, a few months ago, I found several hose connections that were loose. I guess that the synthetic rubber hoses can shrink over time, and they no longer seal well to the hose barb. This can happen even with a hose clamp in place. The solution is to replace hoses as necessary, with new clamps as needed. There is plenty of heat generated under the hood, and it will affect rubber parts, over time.
      Thanks Eric, I checked the hoses and connections but I could not find anything.
      2014 Volvo XC60 T6 AWD R-design: Ferrita DP, DO88 FMIC, Fasttech custom tune, BRC Sequential LPG system, Eibach Pro rear spacers, Powerflex torque rod insert

      2007 Volvo V50 T5 AWD M66 (SOLD)

    10. #8
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      Quote Originally Posted by budleach View Post
      Hard to say without hearing it first hand.

      It is most likely just the turbo beginning to spool. Would be much more noticeable with a tune and the hardware upgrades you did. The conditions under which you say it happens are perfectly in line with this theory. Turbo begins to spool around the low 2000 rpm range, and with part throttle (close to atmospheric pressure in intake plenum) there is sufficient exhaust gas to spool the turbo, but since you are not requesting the boost with your right foot, the diverter valve is being held open to prevent boost build up. Under those conditions the turbo is moving more air than the engine is requesting so some of the air is bled off back into the intake (pre-compressor).

      Tuned turbo cars whistle, it is a glorious noise, embrace it.
      In that case, would an upgrade to the GoFast Bits Diverter Valve be advisable?
      2014 Volvo XC60 T6 AWD R-design: Ferrita DP, DO88 FMIC, Fasttech custom tune, BRC Sequential LPG system, Eibach Pro rear spacers, Powerflex torque rod insert

      2007 Volvo V50 T5 AWD M66 (SOLD)

    11. #9
      Junior Member chrisz's Avatar
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      From FCP Euro parts PVC Diaphragm repair kit:
      Product Information

      When this part fails, your Volvo will emit a high pitch whistle or whine. This is caused by air rushing past the PCV diaphragm due to a rip or tear in the material. The cylindrical PCV valve housing is located in the valve cover oil separator.

    12. #10
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      Quote Originally Posted by chrisz View Post
      From FCP Euro parts PVC Diaphragm repair kit:
      Product Information

      When this part fails, your Volvo will emit a high pitch whistle or whine. This is caused by air rushing past the PCV diaphragm due to a rip or tear in the material. The cylindrical PCV valve housing is located in the valve cover oil separator.
      Hi Chrisz,

      I think it is not the PCV that is failing. The noise does not have a high pitch and it is also not present during idle. I also did not notice a suction from the oil cap or dipstick. I had the PCV fail on my V50 and that was different. There it almost sounded like an issue with the serpentine belt, really a high pitch whistle/whine. The sound I hear now is more like blowing on a bottle.
      2014 Volvo XC60 T6 AWD R-design: Ferrita DP, DO88 FMIC, Fasttech custom tune, BRC Sequential LPG system, Eibach Pro rear spacers, Powerflex torque rod insert

      2007 Volvo V50 T5 AWD M66 (SOLD)

    13. #11
      Member p.rico's Avatar
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      You replaced the intercooler and more importantly the downpipe. Sounds like it's all turbo noise.
      2012 S60 T6 AWD - Vibrant Copper - Premium Package - Climate Package - Multimedia Package - BLIS - Polestar Optimization + Mods galore
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    14. #12

      Whistle under part throttle while coasting

      Quote Originally Posted by hulsenbeek View Post
      In that case, would an upgrade to the GoFast Bits Diverter Valve be advisable?
      If your going to upgrade the BOV go with a dual port. A dual port BOV (blow off valve) is better than a single port unit because it eliminates surge conditions and lag. A dual port BOV uses a valve section that is activated by low pressures, like those encountered during idle or slow speed driving. At higher speeds and pressures, a secondary valve opens to relieve the large quantities of back pressure produced when the throttle is released. Because of the dual valves, the amount of lag during gear shifts is reduced, and dangerous back pressure surges are prevented.
      My car sounds like a cross between a spaceship and a jet taking off...per the wife.


      PS- Youre still gonna have noise the more you tweak things the more noise. Go with Louder exhaust to drown it out. Beers!


      Sent from my iPhone using Tapatalk Pro
      Last edited by paradoxicallymodified; 07-02-2020 at 08:03 AM.

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