Upgrades that create most cabin noise

[jams20]

I have a "new" legacy in the family and hoping to crowd source feedback on upgrades folks have made that negatively impacted cabin noise most - road or engine/transmission vibration. Basically looking to take it from a track focused to road focused. What are your experiences?

I'm also looking at the Sound Deadening FAQ.

[BoozeRS05]

Mounts and bushings - in stock form the car is quiet on the road. If you installed hardened motor, trans or pitch stop mounts it would be noticeably louder in cabin, perhaps along with other various bushings like trans and driveline.

Exhaust - headers, any removed or high flow cats in the downpipe, or any catback exhaust will increase cabin volume. A full stock exhaust has almost zero exhaust note.

Intake or BOV/BPV - intakes and blow off valves will make noise in cabin. Stock form these make almost no noise.

 

Sound deadening - I used kilmat on my entire cargo floor and lined the inside of all 4 doors. I noticed an immediate difference in both exhaust and exterior road noise. Very happy with the time and effort doing it.

That’s all I’ve got right now. I’m sure there’s other things I’m missing. 

[jams20]

Nice. Thanks!  Exhaust, headers and intake are OEM. Any major culprits on the bushings? All are upgraded. (Ignoring motor, trans and pitch stop - i need to check those)

 

Sound deadening - is trying to get under carpet of the footwells low ROI?

[Pleides]

The biggest (and worst) change in overall noise was the transmission mount for me. I have a Group N mount and the mount shares real estate with the exhaust, so if you have an aftermarket downpipe it will get quite loud. I also thoroughly regret the urethane subframe and diff bushings as the diff whine is louder and the subframe bushings all squeak like crazy when warm 2 years later. To lube all of them requires dropping the subframe, so fuck that.

For sound-deadening, on a wagon it will be all concentrated in the trunk. The enclosure created back there by the exposed hatch creates tons of reverb. Getting an exhaust that has tips minutely past the bumper will help a lot as will sound-deadening where the spare tire and fuel door areas are. Putting it in the doors mostly will make more satisfying door thunk noises when closing them and will improve the sound quality of the speakers a good bit too. Under the carpet is actually a pretty good ROI but I would ask a professional shop what they recommend for this. I believe many use DynaMat for certain spots and Dynaliner for other. I'd avoid using the cheap Dynamat knock-off stuff off Amazon as they use butyl which smells awful in the summer. It's what's used to plug tires and is super messy and not fun. You'll get the most ROI doing carpet and trunk if you have finite time and money for deadening the car.

 

Oh, and the stock midpipe is highly recommended if you want to turn the noise level down on the exhaust without making a meaningful difference to power. Mufflers make a big difference as well. For a wagon, if you can find it, the Greddy (discontinued) fits it nicely and is relatively quiet. I have a Borla exhaust and, although it's fairly quiet outside, due to being for a sedan, it has a lot of unpleasant noise created inside due to the exhaust tips terminating well into the cutouts of the bumper. I recently had Surgeline weld longer pipe onto the mufflers and it seriously quieted the interior noise down a ton. I would recommend it, however, if you wanted a more mellow exhaust and could deal with the thing being a bit short. I find the Invidia and other alternatives to just be too loud, especially when combined with an aftermarket downpipe.

Edited October 25, 2022 by Pleides

[TMBLKDG]

Timely post as I'm about to tackle all this kind of stuff in my car.  I have no issues with gutting the interior and putting extra sound deadening everywhere it will help, though I'll start with the cargo area and doors.  The front seats are coming out for repairs and recovering and the console is coming out for addition of double-din stereo and refinishing/repainting so pulling up the carpet and putting down some more sound deadening isn't that much of a stretch at that point.

Glad to hear extending the exhaust tips worked to quiet down the interior.  I also have the Borla exhaust and love the way it sounds but cabin drone is definitely an issue. Going to have the tips extended and also try one of those sound deadening clamp weights that I read about in another thread. Wish I'd bookmarked it 'cause now I'm going to have to find it again, but basically it's a Toyota part that clamps to the exhaust pipe and damps the vibrations of the pipe itself.

jams20 - please update this thread with what you end up doing and how it works for you, I'll be really interested in your results!

[jams20]

Thanks for this! Gives me a check list.

1) check mounts

2) try different exhaust ( current setup is inside lip by a couple inches)

3) cargo Bay insulate

4) doors to make the radio sound better when I turn it up to drown out what doesn’t work

i will keep this updated with results. All others feel free to share as well.

[Pleides]

On 10/25/2022 at 6:36 AM, jams20 said:

Thanks for this! Gives me a check list.

1) check mounts

2) try different exhaust ( current setup is inside lip by a couple inches)

3) cargo Bay insulate

4) doors to make the radio sound better when I turn it up to drown out what doesn’t work

i will keep this updated with results. All others feel free to share as well.

If you stick with a 5-speed and don't 6-speed swap (the 6-speed without a hard trans mount feels about as nice to drive as the 5-speed with the Group N mount) then I still recommend doing the mount just because of how much better than transmission feels with the mount, but if you absolutely detest cabin noise then you gotta skip it. For me, the tradeoff was worth it but if I had to do it again I'd skip the urethane crossmember and all the other subframe/diff bushings to quiet it down and hopefully have the best of both worlds. 

What exhaust do you have? And do you have a sedan or wagon?

[KZJonny]

I have a hard time nailing down which things I did contributed most to cabin noise, but I’ve definitely got some now. Hah.

+1 on how much nicer the 5MT is with the group N mount tho. I would definitely do it again. Also have the (Energy Suspension) poly trans mount bushes, tho I don’t feel they are the worst culprit.

I also have the sedan Borla exhaust and while the note is nice, I agree that the tips being recessed can’t help. Considering welding in some short extensions to see if it helps. Cheaper to start there then replace the whole (new) system.

[jams20]

4 hours ago, Pleides said:

If you stick with a 5-speed and don't 6-speed swap (the 6-speed without a hard trans mount feels about as nice to drive as the 5-speed with the Group N mount) then I still recommend doing the mount just because of how much better than transmission feels with the mount, but if you absolutely detest cabin noise then you gotta skip it. For me, the tradeoff was worth it but if I had to do it again I'd skip the urethane crossmember and all the other subframe/diff bushings to quiet it down and hopefully have the best of both worlds. 

What exhaust do you have? And do you have a sedan or wagon?

I am a new owner of a wagon. (started w/ a sedan) On it i believe is an OEM sedan exhaust. It terminates a couple inches before the end of the bumper. I have the HKS Silent Hi-Power exhaust for the wagon i mistakenly purchased for the sedan. Looking to install this but apples-oranges when it comes to noise level vs stock. 

[Pleides]

1 hour ago, KZJonny said:

Considering welding in some short extensions to see if it helps. Cheaper to start there then replace the whole (new) system.

This is pretty much what ya gotta do. Surgeline used maybe 3 or 4 inches(?) of pipe from my tips to the muffler and it made a good bit of difference. I did get used to it very quickly, but you do notice it, especially when you start the car.

[NORULZleggy]

You have the same car I have and year. It is going to make noise no matter what you do haahaha lol. People think my car has a dog box as loud as the trans is on decel. It perfectly fine it due to the mounts I put in the car. I have a full JL system So i do not hear any weird Subaru noises. I am also full external wastage so it's loud. Either keep it stock or mod it and live with it. these are old cars ands they will make noise. I love it!

[boxkita]

that wagon is noisy. every bushing is a motorsports part.