SL55 AMG, SL63 AMG, SL65 AMG (R230) 2002 - 2011 (2003 US for SL55 and 2004 for the SL65)

SL55/63/65/R230 AMG: SL65 strange sound when letting off the throttle (VIDEO)

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Old Aug 23, 2016 | 04:05 PM
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SL65 strange sound when letting off the throttle (VIDEO)

Whenever I let off the throttle quickly/sharply, I get a strange noise that sounds like a dying goose for lack of better words. If I let off the throttle slowly, I get the normal whoosh noise from the BOVs without the strange noise.

Any idea on what's causing this? I do have the Speed Driven BOVs and open filter intakes.


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Old Aug 23, 2016 | 04:12 PM
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That's a very unorthodox way to drive (mashing the throttle with no downshift then suddenly letting off before the boost kicks in?), but that sounds like it's the BOVs trying to cope with a sudden drop in throttle at low boost (higher boost = more air = the higher-pitched, more "normal" sound).
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Old Aug 23, 2016 | 04:27 PM
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Thanks for responding. Obviously I don't regularly drive that way but I was just trying to demonstrate the noise that it makes in a controlled and repeatable fashion. It does happen during regular driving as you'd normally take your foot off of the accelerator quickly instead of easing off of it slowly when coming to a stop. Is this normal normal behavior for this engine or is this something amiss here?
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Old Aug 23, 2016 | 04:37 PM
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Originally Posted by B Feelgood
It does happen during regular driving as you'd normally take your foot off of the accelerator quickly instead of easing off of it slowly when coming to a stop. Is this normal normal behavior for this engine or is this something amiss here?
I've never heard it that way, but if there's no codes and you have full boost (no boost leak/sticking valve) I don't what to say. Would have to ask the smart people ... by any chance, are you in manual mode?
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Old Aug 23, 2016 | 09:57 PM
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your aftermarket bovs?
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Old Aug 24, 2016 | 01:36 PM
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Honestly sounds like the turbos surging.
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Old Aug 24, 2016 | 01:55 PM
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Originally Posted by euphoriaDSM
Honestly sounds like the turbos surging.
It's hard to say because the "mash the throttle, but let off real fast before boost can build" driving technique he's using to force the sound is weird, too. I don't think that's a usual sound.
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Old Aug 24, 2016 | 02:40 PM
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Originally Posted by Speedriven1
It's hard to say because the "mash the throttle, but let off real fast before boost can build" driving technique he's using to force the sound is weird, too. I don't think that's a usual sound.

Whenever I bought these BOVs one screw was tightened all the way down and the other was turned about 3/4 of the way down. Do these screws adjust the tightness of the spring inside the BOV? I'm pretty sure I have a picture of the day I received them, give me a minute to find it.
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Old Aug 24, 2016 | 02:45 PM
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Originally Posted by B Feelgood
Whenever I bought these BOVs one screw was tightened all the way down and the other was turned about 3/4 of the way down. Do these screws adjust the tightness of the spring inside the BOV? I'm pretty sure I have a picture of the day I received them, give me a minute to find it.
No, they don't - obviously if one backed out that's not ideal.
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Old Aug 24, 2016 | 02:58 PM
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Originally Posted by Speedriven1
No, they don't - obviously if one backed out that's not ideal.
This is what they looked like the day that I received them. I remember trying to tighten the one that was backed out a bit to match the one that is screwed in all of the way but it wouldn't budge and was starting to round the nut, so I just let it be.





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Old Aug 24, 2016 | 03:03 PM
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I thought you meant one of the 3 bolts on "the side". That shouldn't make a difference.
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Old Sep 4, 2016 | 10:01 PM
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Originally Posted by B Feelgood
Whenever I let off the throttle quickly/sharply, I get a strange noise that sounds like a dying goose for lack of better words. If I let off the throttle slowly, I get the normal whoosh noise from the BOVs without the strange noise.

Any idea on what's causing this? I do have the Speed Driven BOVs and open filter intakes.


20160816 092149 - YouTube
My car makes the same sound. I think it's normal.
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Old Sep 5, 2016 | 01:21 PM
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Originally Posted by boostd
My car makes the same sound. I think it's normal.
Thanks for the response! Since yours does it as well with similar mods, I won't worry about it. I'm accustomed to the normal woosh noise from other turbo cars but not that particular noise in the video. Especially from a recirculating BOV that doesn't vent to the atmosphere.
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