As some of you know I recently installed a Bisimoto exhaust on my 2019 Fit Sport, documented here. I am happy with the exhaust except it is waaay too loud inside the car. Outside it sounds really good, not super loud, but inside the car it is a different story. I like the exhaust and want to keep it but wearing earplugs on my 40 minute commute is not an acceptable solution. So I decided to try some sound deadening measures to see if they help.

I decided to combine three different solutions:
1) Sound Deadening Butyl Mat - I chose a 36 square foot pack of over some other brands based on price and reviews.
2) Mass Loaded Vinyl (MLV) - I used a 4' X 4' roll of .
3) Rubberized Undercoating - My local Autozone had on sale so I bought a bunch of cans...

I haven't gotten to the undercoating yet, but today I installed the Noico mat and the mass loaded vinyl (MLV) mat.

The foil faced Noico mat came in the form of nine 4sqft pieces. It had a paper peel off on the back to expose the very sticky butyl rubber backing. The MLV mat has no adhesive backing.

Other than blowing debris out of the spare tire well, I did no other prep to the painted surfaces. The Noico mat was relatively easy to work with and stuck quite well.


I ended up using all 9 pieces of the Noico. I did cover the metal under the carpet under the back seat hump, and I doubled up the mat in the area above and near the exhaust.








If you look in the background of this pic you will the wife's Pampered Chef rolling pin which I liberated to roll the mat. A trip to the dishwasher and it will be good as new...


No pic of the MLV mat but I used my all weather rear cargo mat as a template to trim it up. I then installed it on top of the foam jack holder (on top of the spare tire). I put the rear carpet and cargo mat on top of it.

I put the rear seats back in but I haven't reinstalled the side trim panels yet (I left them out because I need to pull the rear shocks and install the shorter bump stops that came with my sweet Eibach lowering springs...). After doing the partial reassembly I took the car for a ~20 minute test drive.

I am pleased to report that the mats have made a significant improvement in interior noise levels. For starters, my ears were not ringing when I returned from the drive. I installed a db meter app on my phone and tomorrow I will make some comparisons with today's commute.

Please understand that the exhaust is still loud (certainly significantly louder than stock), but for me it's a question of how loud is too loud. It is much better now, and hopefully a liberal dose of undercoating will help bring the noise in the cabin down just a bit more...

 

what were the decibel readings prior to sound deadening?

 

and all that was necessary....

 

 

Looks great!!! Glad it helped!!!!

If you ever get tired of the noise I'll gladly drive down to you and buy the muffler from you lol.

 

I tried to compare yesterday's commute with today's and it was just too difficult to put a number on it. The rain, the traffic, different speeds, rpms... I just didn't have the patience to put any real scientific rigor into any of it...

I did that for a few days but not acceptable in the long term.

da da da...

Thank you for the words of encouragement. When you say "noise" are you referring to da sounds of a dying vacuum cleaner with a megaphone?

Seriously though the exhaust sounds really good, just too loud inside the car. The sound deadening mats have really helped, but today I decided to implement a 4th approach to further reduce interior noise from the exhaust.

I filled the rear fenders and wheel wells with a total of 6 cans of Great Stuff spray foam.


I put 4 cans in the passenger side and the other 2 in the driver side.




I have not yet gone for a test drive, but I did start the car up and rev it up; the difference is unbelievable. In terms of reducing exhaust noise inside the car, this may have made the biggest difference! Once I am able to go for a proper test drive I will know for sure, but I believe this may be the ticket for reducing interior exhaust noise in a FIt...

 

Wow - be really careful with that foam. It will expand between interior support beams and the body and can actually cause distortion of the body panel. A little goes a long way. Some of the DIY Sprinter RV guys found this out the hard way...

 

uhhhhh ... I am not sure what to look at first here

Ok so first of all nothing you did looks disastrous and I am SURE it will cut down on your noise a ton! Now, onwards ..

=Not that it matters now but you probably can get away with 1/3 the Noico stuff. The point is to prevent panels from vibrating so as long as your strips are sufficiently long AND are covering most of the flat areas, that is good enough. Beyond that, my belief it, it's just weight. That said, aside from the weight and cost it is not BAD to use more.
=MLV is most effective when there is not much gap between the body panels and the MLV (I think there is supposed to be a very thin layer of separator material). I think it will work OK to just cover the flat cargo cover, just not quite as well.
=Spray foam - I wouldn't put that behind the wheel well cover due to moisture concerns. Rust you know. However it is relatively waterproof itself so maybe you'll be OK. I would watch out for spraying too much in ... it really does love to expand!

 

lol u folks are too nice.

 

The foam expands; good gauge...

Tepid approval? Tacit Flaming? Both? Da Blogga tinks u 2 nice?

 

I appreciate your efforts.
I really do.
I know exactly how this works. Once I am set on fixing something, often I will stop at nothing - it is so easy to pass the point of no return.
I call it an eternal struggle - man versus machine, and the machine shall not win.
I understand.
But i just have to say, that between parts and labor, this is turning out to be one expensive straight pipe setup...
Still, I applaud your commitment to making it work.

 

This seems like an awful lot if work to mute something that has the sole purpose of being loud.

 

Including the undercoating I will have spent ~$180 on the effort. I would like to point out that my primary reason for the effort was to quiet the interior of the car (yes, the Bisimoto was the catalyst for the effort). However, with or without the exhaust, I would argue that efforts to quiet any Fit's interior have benefits. I don't believe you'll find many Fit owners wishing their car's interior was louder; it's not excessively loud but it's no vault.

In another recent thread I documented the replacement all the stock stereo speakers and installation of a powered subwoofer. The sound deadening efforts I've done here will certainly add value to that stereo system upgrade. I am honestly a little surprised at the decidedly negative tone of the feedback this effort has received; everybody's got opinions...

 

 

I enjoyed reading this thread and seeing your progression towards achieving a less-loud interior. Thank you for posting pictures on what you have done.

Personally, I need a device that lowers the noise coming from my kids in the backseat. xD

 

UnFitRick - From experience over the years with under-body coatings.. Take a really good look to make sure you don't go over any drains. Car companies engineer in drains at "pinch seams" where two panels come together. Really think hard about where water will sit, etc... Those sprays, if used incorrectly, can trap tons of moisture and do the opposite of intended. Thanks for the links on the stuff you used!

p.s.. You are doing this to a 2019. Have you ever been in a 15,16, or 17? The sound deadening effort at Honda was miraculous when they made the 2018. My 15 sounded like any economy car made in the last 20 years. My 2018 is as quiet as a Honda Accord would have been 10 years ago. My 15 was road and engine on the interstate. My 18 is just common wind noise. But you have me curious now if I can improve even more.

 

CyclingFit - totally agree about the 2018+. Our '18 is certainly a lot quieter than our 2011, particularly on the highway, which makes me want to look for noise solutions for the 2011. The 2018 has much better engineered damping with the shocks/struts (not just compression/rebound but also the urethane bushings used on the shocks) as well as revisions with glass and likely the body panels/structure.

However, I do notice a bit of a "drumming" type road noise from the rear in the '18, it seems that the hatch area is the most in need of some sound deadening. UnFitRick's solution with the butyl sheets seems like it would really help with this, both adding mass as well as deadening and insulation - I was thinking about this a couple weeks ago, looking into Dynamat or similar. Glad he was the pioneer and found a much less expensive solution.

 

I have never driven my 2018, or really even the 2015 without my custom homemade cargo mat in the back. I am wondering if it helps a lot more than I have ever realized. Instead of a cargo tray, I have a piece of truck bed cargo mat. I traced cardboard and then cut it out. It's crazy heavy and nothing I put in the Fit could ever hurt it. My friend buys the full size truck liners at our local farm store. The auto parts store he manages has maybe 10 Honda Fit's of different eras for deliveries. He lowers the magic seats and then custom cuts the truck bed mat to cover every square inch from the front seats to the hatch since the cars will never in their life have a reason to raise the magic seats again. Long story just tell you that he gave me one of the leftovers so I could do just the cargo area and I bet it deadens a ton of sound.

 

Funny, in a few years you'll be wishing they were still back there making noise... or maybe not.

Good gauge on the undercoating; I will be watchful and document any findings. And no, I've never been in an older Fit. In fact I never test drove or even sat in a Fit before driving this one home from the dealership. I presume, among other things, the older Fits didn't have that funky fabric-like liner material in the wheel wells and underneath? Someone here said their new 2018 Fit LX didn't have it either? Speaking of the wheel well liners, my intent is to remove them, undercoat and re-install the liners, probably...

Speaking of the butyl sheets, I just ordered what should be enough to do the 4 doors, along with some foam baffles for the door speakers. While replacing the door speakers (after a few days of rain), I found the backs of the speakers to be wet...

 

Nice - was wondering about the doors, too. Can't wait to see some install pics. I suspect it will be a bit tricky to place the sound deadening sheets inside the doors.