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Need help diagnosing an unpleasant new sound, posting brief audio clip below (hopefully). This only occurs under heavy boost…assuming it is some form of turbo death, though I have no codes and car still runs well (so far). Any thoughts/suggestions? No noise on deceleration, or at idle
It would be worth logging the car I think to see what the wastegate operation is and to see what the boost is doing, under boost or over boost, though you're right, you should get a code for that. If there's leaks in the system, they may not be bad enough to trigger a code and like you said the car seems to pull aggressively. Additionally at the fundamental level with 71,000 miles on a tuned car this could just be bad internals of the turbo, deteriorating bearings, etc.
Yeah, that definitely sucks if that's the case but it could be something else that may be less expensive to repair or remediate.
if your turbo charger starts sounding like a supercharger, that's usually not a good thing
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
On older turbo cars, that sound is associated with a torn diaphragm in the diverter valve. Not sure how Mercedes handles that, but it sounds like a boost leak.
On older turbo cars, that sound is associated with a torn diaphragm in the diverter valve. Not sure how Mercedes handles that, but it sounds like a boost leak.
Dies the diverter function to relieve over boost condition? This would seem most plausible for my scenario, where only experiencing the sound at or near max load/boost. That said, the Tasos videos I’ve watched mostly show that piece actuated by the wastegate rod…maybe this is correlate to diaphragm?
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by Jaybird123
Dies the diverter function to relieve over boost condition? This would seem most plausible for my scenario, where only experiencing the sound at or near max load/boost. That said, the Tasos videos I’ve watched mostly show that piece actuated by the wastegate rod…maybe this is correlate to diaphragm?
The purpose of the diverter valve (DV) is to relieve the back-pressure on the turbo when shifting. On a manual transmission, the throttle plate in the throttle body momentarily closes as you take your foot off the gas to shift. Granted, that happens quickly, but the turbo is still pushing air and without the DV diverting the boost back through the intake, it's like the turbo hits a brick wall. (Among the boy racers that use blow-off valves instead of a DV, boosted air is relieved into the atmosphere and we have global warming.) Same thing happens with automatic transmissions, only much quicker and you probably don't realize it is happening.
Similarly, the wastegate which is controlled by the wastegate actuator, excess boost is bled into the exhaust stream to reduce the boosted amount going into the engine. The wastegate is intended to limit maximum boost, while the DV is to relieve a momentarily over-boost situation. However, the DV typically routes the boost back into the intake to the turbo (not the engine) downstream of the MAF/MAP.
I really appreciate that explanation, makes sense to my aging noggin! The symptom totally disappeared per tonight’s dinner outing, and the only thing I did was redo all my charge pipe connections and tighten hose clamps. Maybe that back pressure was causing a leak noise? My gf said it sounded like when you let air out of a stretched balloon though not as high pitched…
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