Sound deadening solutions

[njintau_fsd]

Hi everyone!

Well, a while ago, I replaced all of my motor mounts with Polyurethane ones and well since then the noise from the engine is gotten pretty bad. While I can take it when I'm driving around town, in the highway it gets really bad. Past 4000RPM its so loud that I can't stand it anymore. I was thinking about removing the carpet in the front and line the floor with some kind of sound deadening material. Anybody have any brands/type of material suggestions? Can anyone think of any other solutions?

Thanks in advance!

[1Mazda323Fan]

Dynamat might work. Or, steal some tar from the local DOT supply and slather it on the floorboard and firewall. Other suggestions: switching back to rubber mounts, puncturing your eardrums.

[goldstar]

Sorry, I can't help you with your problem but I can tell you what caused it. Go to:

http://www.wihandyman.com/forum/showthread.php?t=47032

Happy Motoring!

[MazdaNoob]

noise or vibration creating noise. there is a difference.

i have 90 duro mounts front and rear and have little to no issue above 1000 rpm. engine noise over 4000 rpm is all intake and exhaust noise really as things smooth out. i dont think your issue is the hard mounts.

[njintau_fsd]

Thanks for the reply guys! Sorry it took so long for me to reply lol

Goldstar, I'm not sure if its the engine per say since I just rebuilt it. I figured the builder balanced the crank when that was done. Mazdanoob, the sound problems have been around since I installed the poly motor mounts. There's a lot of vibration right around where the pedals are. Heck, when I open the doors when the cars idling, the doors would actually rattle.

Anybody out there tried Second Skin? I guess I'd just have to gut the interior and apply some sound deadening mats and/or spray the interior with a liquid lining of some sort...

[DuRWooD]

Thanks for the reply guys! Sorry it took so long for me to reply lol

Goldstar, I'm not sure if its the engine per say since I just rebuilt it. I figured the builder balanced the crank when that was done. Mazdanoob, the sound problems have been around since I installed the poly motor mounts. There's a lot of vibration right around where the pedals are. Heck, when I open the doors when the cars idling, the doors would actually rattle.

Anybody out there tried Second Skin? I guess I'd just have to gut the interior and apply some sound deadening mats and/or spray the interior with a liquid lining of some sort...

Despite even a perfectly balanced rotating assembly on an inline 4, there are secondary harmonics due to the pistons moving at different speeds throughout their stroke, this leads to a natural imbalance. Stiff motor mounts make this felt in the car, while soft motor mounts dampen it.

[njintau_fsd]

Oh I see, thanks for the clarification...

[MazdaNoob]

i was asking for clarification whether your complaint was engine noise or vibration .... because the two are very different . you mentioned that the vibration started when you installed the mounts . @ idle and up to about 1000-1500 rpm my mounts make the car rattle like it's falling apart . but after 1500 rpm it's as smooth as my suspension allows so yes at idle with the doors open it's LOL .. but in your initial question you mentioned it got worse with rpm and louder over 4k .. that is not the mounts . you have either a balance issue or something else occurring

[njintau_fsd]

Hmm, I do have the "car falling apart" vibration too at mazdanoob but there's consistent vibration right around where the pedals are at higher rpms. I do admit that the engine does smooth out at higher rpms but the sound remains. I'm starting to think that its the exhaust and I just never noticed until I added the poly mounts. And... I guess the balance issue is possible, maybe the engine builder didn't do a great job balancing the crank. I'm also wondering if the forged internals are adding to the vibrations however...

[meGrimlock]

any update on the NVH? i just had some RR-Racing poly inserts installed on the rear mount and it does sound like i put on a "fast/furious" muffler on the car. the noise and shakes were expected but is it going to settle over time? i'm assuming since the rear mount is on the firewall most of the engine NVH will transfer thru the cabin that way. i might remove them in the future and just install the poly inserts in the front mount.