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Discussion Starter · #1 ·
I have a 2016 GLA45 with the U21 AMG sport exhaust. I have noticed that the car is quieter and does not pop and crackle as much as it did. I thought it may have been a faulty exhaust flap actuator motor so I replaced it. This has had no effect. Any suggestions on what to check next?
 

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U21 was marketed IMHO in a less than ethical way. The extra sound is via a sound box on the firewall that transmits the sound into the cabin. If the valve in the front of the car is not working to open the exhaust to the box then you will get the quieter sound.

Pops and crackles are also a function of Sport mode
 

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Discussion Starter · #3 ·
Thanks for the insights. I forgot to mention I drive generally in S mode. My question now is, can I get to the sound box myself and check if it is functioning correctly?
 

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I had the same "fake sound" in my Audi TTS. In that application it used the inside of the windshield to resonate-augment 'performance' sound.

There's only so much that can be done with a 4-banger and AMG has pretty much squeezed everything they can out of it in the '45. Actually amazingly so.

The snap, crackle, pop is pretty typical of these maxed out-four configurations. Related, many Porsche Boxster/Cayman owners lament the sound since migrating from their quintessential naturally aspirated 'boxer' flat-six to the current turbo-four. It's all about instant gratification off the line torque these days (slight turbo lag notwithstanding), rather than the historical high sustained rev-ing maintaining the power band. 🤷‍♂️
U21 was marketed IMHO in a less than ethical way. The extra sound is via a sound box on the firewall that transmits the sound into the cabin. If the valve in the front of the car is not working to open the exhaust to the box then you will get the quieter sound.

Pops and crackles are also a function of Sport mode
 

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Thanks for the insights. I forgot to mention I drive generally in S mode. My question now is, can I get to the sound box myself and check if it is functioning correctly?
yes, dig around for some posts by hubachek, its a module about the size of a fist on the firewall driverside
 
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