Roastie

How is it that an exhaust system can "break in?" Many report that their new exhaust is a bit loud or raspy but changes to be quieter and mellower over time. I'm not doubting that this occurs, especially with so many reports of this phenomenon, but I just don't understand why it would change.

After all, an exhaust is just a pipe, and a muffler is a pipe with baffles. No moving parts to wear in together, and any changes in size or fit should be insignificant.

Thanks in advance for answers.

Regards,
- Confused

PSS // Raj

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Avantadrive_Original

I have a "new" exhaust (although I have broken it in), and I can tell you that there is a residue on the innner part of the pipes that causes not a "raspy" sound, but a less loud sound and causes less air flow. After several months of use or about 500 miles depending on the exhaust, that residue pretty much wears away, allowing exhaust to flow through with minimal restriction- that's when you get the best sound and the best performance!

Another Drew

<p>Andrew Lee
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Jardo

My stebro back end sounded almost stock at first. After 3000 - 4000 kms it mellowed and grew slightly louder. It had a new muffler smell for a 1000 kms or so but that is now long gone.

In addition I noticed four things with the stebro
1) nice polished tips that fit perfectly
2) mellow deep sound that you can control the volume with the throttle
3) don't know why but gas mileage increased approx 10% immediately after the install
4) power over 4000 rpm is now delivered evenly and more quickly. the engine does not feel like it is being restricted.

A4 00 1.8tqms stebro brilliant yellow