Exhaust valve
07-04-2024, 09:27 AM
#1
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C63 s204
Exhaust valve
I have a stock s204 2012 p31.
When the car starts there is first the growl and after that, if it was a cold start, it first idles a couple of RPMs higher for a short amount of time before returning to normal idle.
However, after a couple of seconds on normal idle, the sound suddenly changes and goes from a raw/metallic sound to almost silent.
I was wondering, is there some kind of valve in the exhaust that is automatically operated? Or what is causing this change in sound?
When the car starts there is first the growl and after that, if it was a cold start, it first idles a couple of RPMs higher for a short amount of time before returning to normal idle.
However, after a couple of seconds on normal idle, the sound suddenly changes and goes from a raw/metallic sound to almost silent.
I was wondering, is there some kind of valve in the exhaust that is automatically operated? Or what is causing this change in sound?
07-04-2024, 02:34 PM
#2
Super Member
No valves, that cold start bark is extra fuel being dumped by the injectors since cold engines need to run rich to get started. Once warm enough, the sensors tell the EFI not to dump extra fuel because it's no longer needed.
