Roaring exhaust

[Chanteure]

Hello!

I have an issue with my Toyota Aygo (2006 5DR) VVT-I. Recently my local garage changed the centre section and the silencer as it rusted and was making loud sound even when on idle. However, just recently noticed that a roaring sound reappeared, however, you can only hear it when you reach a certain RPM and soon as you hit lower/higher RPM the sound disappears. I can certainly hear it coming from the back (exhaust), usually, if I'm doing 30 on third gear I'll start hearing the sound. Any advice on this?

Thanks!

[Vandals01]

Personally, if it's okay at Idle, I wouldn't worry about it.

It is normal for a silencer to filter out some frequency, but left some untouched.  Especially I assume it is an After-Market silencer that could be lower quality.

To understand how a silencer works, here is a video:

 

[Guest]

A new silencer will not have any soot in it (se picture above) so will be noisier until some soot accumulates, so what OP is describing sounds(!) perfectly normal to me.

[Chanteure]

Hey guys, thanks for the replies! 
I am fairly certain that the sound is not normal as before I couldn’t hear it. It sounds like rattling/roaring.

[Mooly]

I'm wondering if these were genuine parts or after market 'equivalents'? 

If the latter then they may well have a totally different 'sound' to the originals.

 

 

  

[Chanteure]

I believe they are not original, however, the sound is all fine up to and after certain rpm. For example if I do 30 on third gear it will start to rattle just before I reach 30 and it will sound normal once I do 32mph. I do not know if that makes sense but that really does not sound normal and sounds like metal rattling.

On idle and low rpm it sounds completely normal, even at higher RPM it sounds normal, but there is that specific moment where it starts rattling.

[Mooly]

I suspect that might be a typical symptom of a non original design tbh. It will behave differently to the original at different gas flow rates and may resonate in some way that the original does not. There is no easy way to prove it unfortunately without substituting it for the correct fitment.

It is also possible that there is a on off issue with the replacement (it is faulty in some way) or that there is some issue with the actual physical fitting of it that causing some kind of resonance but I suspect it will come down to being a non original part that is the cause.

 

   

[Vandals01]

6 hours ago, Mooly said:

I suspect that might be a typical symptom of a non original design tbh. It will behave differently to the original at different gas flow rates and may resonate in some way that the original does not. There is no easy way to prove it unfortunately without substituting it for the correct fitment.

It is also possible that there is a on off issue with the replacement (it is faulty in some way) or that there is some issue with the actual physical fitting of it that causing some kind of resonance but I suspect it will come down to being a non original part that is the cause.

 

   

Besides, unless it comes from anything that is BEFORE the Catalytic Converter, it would be pointless to fix.  Because after CAT, all it does is dampen the sound.

MOT will not fail just because your car roars at certain RPM.  It will only fail for broken hangers / section missing or falling apart.

[Chanteure]

It passed the MOT recently as well, however, the MOT was also carried out by the same garage that changed the exhaust 1 month prior.

Yesterday I've checked if the hangers are properly fixed etc, however, it seems that everything is done correctly. 

[Billyboy81]

I get a droning noise at exactly 65 mph on the motorway. Anything less or more it goes away. It's still there after having the rear box replaced recently. I think what you are hearing is resonance at a particular rpm. Nothing to worry about. 

[Chanteure]

Update, got it fixed today. It was a faulty muffler.

[Mooly]

Excellent. Pleased to hear you have it sorted.