[Mégane III] Loud engine

Hi guys, sorry for writing in English, but I'm from Croatia and I thought that someone here might me able to help

My problem is:

I bought a used 2009 Megane Coupe 1.6 16V a couple months ago and the only thing that's bothering me is the loud engine. The guy in the local Renault dealership told me that the sound is normal but I'm not that sure.

The engine gets really loud in the 3500 - 3900 rpm range while driving. Above and below this range the level is acceptable, so I'm guessing it's some type of resonance. I would describe the sound as normal engine sound only loud. For the geeks -> The sound is fairly low in frequency -> Around 150 - 200 Hz.

It would be quite weird that this is normal because everyone notices that my car is loud, i.e., I'm not imagining things

Is this normal or can it be "fixed"?

Thanks a lot!

salut

peut etre un support
maintenant reste a savoir lequel (moteur / bv / couple)

Hi ReDRuM and welcome

it's rather normal to get a resonance at this engine speed range on petrol engines

At 3900 rpm, the frequency emitted by engine combustion is 3900 * 2 /60 = 130 hz
Have you measured the 150 hz or, just estimated?

I also notice a noise increase on my own Laguna at 4000 rpm, even it's equpped with a flexible flywheel, which is aimed to reduce this kind of resonance noise.

Thanks a lot for answering.

Yes, I estimated the frequency. I measured it today with an RTA and you are correct.

What I find weird is that it's noticeably louder within this one rpm range (cca 3600 - 3900)...

Can this be "fixed" somehow? I heard that Renault used to install some kind of soundproofing material under the front hood of the car, and that you can still buy it as an option. Do you think this would help?

To me it seems that the vibration/sound is transferred through the chassis itself and I'm not sure if the soundproofing material under the hood would help much.

Thanks.

I also guess that no soundproof material can efficiently reduce this kind of noise

You may want to check the quality of the silent block(s) holding the engine, as advised by Bib30600
But in my case, the vibrations transferred to the chassis were max at idle RPM (about 750rpm) due to degraded silent block.

Hm... But do you think this could be normal? That the engine is noticeably quieter at slightly higher rpm?