Well, I've got an aftermarket exhaust installed this week, and I love the way it performs and the way it sounds on the outside... It's the inside that's bugging me a bit.

Today was the first time I got it on the freeway and opened it up to 'normal' highway speeds, and above 75 ~ 3250 rpm, the drone was quite annoying and loud. And the Milltek is supposed to be the 'quietest' system, compared to other dual muffler cat-backs. Heh.

Well, it's not painful loud or anything... But I want to install an A/V system in the car, and the mufflers/exhaust are definitely going to interfere with 'enjoying' music & video.

A buddy of mine says I can put 'dynamat' type materials above the mufflers to dampen out most of the resonance (noise caused by vibrating parts), but I'm not sure that's the best way to go. Was going to put this in Nav/Audio forums, but my primary concern prior to the A/V install, is to try and 'nerf' the sound in the cabin, coming through the underside.

Any tips or ideas?

 

Dynamat on the inside of the floor from the cargo area forward to under the rear seats will go a long way.

Also do something in the area of the rear hatches, like put real carpet on the inside of the side cubby covers (sound gets in through the taillights).

Don't forget to Dynamat the inside of the tailgate.

 

Oh... I also forgot to ask. What kind of Dynamat?

"Dynamat" the brand is expensive. 2 prefab door cutouts are like $100 at Best Buy. I've heard of other good stuff a long time ago, that is pretty much a 'generic' version, but you could buy it in large rolls.

And would all of it need to go inside the vehicle? Or any special material for dampening the exhaust?

 

If the noise is that objectionable the tips are probably vibrating against the lower trim or one of the cans is contacting the heat shield. These are two issues I’ve experienced with both of the Millteks I’ve had. If the tips are contacting the trim the first thing to do is remove the rear cans, bend the hangers to try and gain some distance from the plastic and if that doesn’t do it, trim the vinyl valance and re-install with the tips as receded as possible. If that still doesn’t provide enough clearance then you will need to use longer rubber exhaust hangers available at auto parts stores.

If it is indeed cabin resonance then sound-deadening material will help suppress the drone. I’ve used a variety of deadening materials and the easiest products to work with are the B-Quiet ones. http://www.b-quiet.com/. Twelve feet will do the boot hatch and boot floor in double layers. Fifty feet will do the door skins, rear hatch door, quarter-panel skin behind the taillights, area behind the speakers and single layer on the boot floor. It is far better to get 100 ft and do double and triple layers on the complete rear floor and boot door as well as single layers on the areas behind the panels and open areas on the panels themselves. The battery box interior also benefits from an application. Any place that vibrates will be a good place for the material. I use thermal insulating material in the battery box, behind the taillights, and stuffed into the frame openings. Placing a sealed barrier behind the taillights is highly effective. You will need to get extras of all the clips, nuts, rivets, and screws that secure the rear panels, door panels, the speakers, and pillar covers. Some will be damaged when parts are removed and others will be missing or damaged from the factory. I have a few other helpful tips for this job if you need them.

 

I don't think the tips are touching the trim, though I'll have to check on the heat shield theory:



Thanks for the B-quiet link. That the type of stuff and price range I'm looking for.

And of course more tips are welcome. I'll need as many as possible to deaden the sound and prep the cabin for the A/V install.

 

You'd be much better off in an audio forum. They're the guys that know about this stuff.

I'm curious though... if you spend several hundred dollars for an aftermarket exhaust, then a couple hundred in sound damping material, which is very heavy and negates any performance gained from the exhaust... what was the point?

 

http://www.mcmaster.com/nav/enter.asp?pagenum=3274

"Generic" dynamat at about 1/3 the branded price. Scroll down to "adhesive-backed damping sheets". They even offer a 1/8" thick version that should remove any need for multiple layers.

 

Let just guesstimate for S&G's that the milltek complete system gives you 10+ over stock.

I don't think 10 lbs of sound dampening material will hurt it any.

And if it did, it's kind of moot, because I'd likely install the material for my AV install anyhow, just not as much.

 

PM sent. Try some venturis.

 

I saw some fins you put between the exhaust flanges which kills the exhaust noise.. used to be a popular item in oversea markets.

 

Your tips look like they are close to the trim. Was the shot taken when the tips were cool? I know my tips expand when they warm and get closer to the trim. What I did to drop the tips was to use three 5/16 washers on each bolt holding the exhaust hangers. This dropped the tips further away from the trim.

Another problem I have with my Milltek is the cheap clamp provided. I have tightened it up as tight as it will go when the exhaust was cool and warm yet I still get a leak from the section which slides together. I'm not sure if you have the same clamp as I helped a friend install his Milltek last week and a better clamp was provided. If your getting a small leak, this can cause extra noise.

Here is a shot showing the amount of drop using the washers.

 

Ten pounds isn't much. I guess I was picturing you doing the whole car is viscoelastic, which would weigh considerably more.

 

The pic was taken cold, right after the install, before the first start-up. Good idea to drop it down some though. I'll look into that. I'll also take a peek and see where the tips are sitting before I go home, and when I get home, to see if they're touching, or if there's any changes in-between.

Not sure about the clamp. The inner pipe had a couple of slots in it, and the outter pipe had none, but was wider and came with exhaust grease. Put about 1/8 worth of grease on the outter pipe, about 4" in. During first startup, had a lot of condensation/steam coming out of the exhaust, and I took a good look at that joint for leaks, but didn't see any then. Don't know how I'd look for leaks now. Obviously the car would need to be on, but I don't know how obvious a small leak would be.

Only pic I have of the clamp is in my gallery. It's on the left end of the pipe sitting on the instructions on the right. :P

http://www.mappage.net/cmine/albums/milltek/006.jpg

Thanks for the info/tips all!

 

To "dampen" your exhaust, just go for a drive in the rain - that will get it good and wet.

If you want to "damp" the noise, use dynamat...

 

Watching this thread closely. Found a Milltek under the tree Christmas morning. (Well, near the tree!) Haven't installed it yet...

FWIW, my clamp looks like the one in Wagnbat's photo. I thought it looked pretty beefy, compared to what used to come with Brit sports cars.

 

:impatient :impatient :impatient

Dampening

 

You got the good clamp, Wagnbat. So that shouldn't be an issue.

One way I know when mine was leaking is I heard a popping noise from under the car while warming it up one day. I looked and condensation was dripping from the joint.

 

A layer under the rear seat works well and is easy to do.

 

Checked under the car before leaving work (cold) and after driving 20 miles (warm)...

Tips do not touch valence or anything else. About 3-4mm of clearance at closest point.

Mufflers do not touch heat shields, about 1mm of clearance at closest point, but definitely not touching.

Looks like sound dampening is the next step, unless increasing that 1mm muffler can to heatshield cap helps.

Had the windows down for a bit too. Sound is much more tolerable. So it's only when the cabin is buckled down, and under accelleration or over 75.

 

I had the dreaded drone (and it will drive you nuts) with the Rogue exhaust. Dynomatted everywhere with the heavier weight stuff. Went around knuckle rapping any surface to see if it vibrated. It helped, and definitely made my stereo sound better (upgraded speakers, Alpine HU). What really killed the drone was installing a resonator in the straight pipe-I used a $35 Spiralflow from Summit.
Eventually went to a custom exhaust, keeping the Spiralflow and using Supersprint cans. No drone.

 

did you have your rear seats up or down? it makes a huge difference.

 

Both. And it's about the same.

And will keep that in mind jlm, thanks.

 

There was another discussion about an injectable foam in the following thread:

https://www.northamericanmotoring.co...highlight=foam

You might find this of interest

 

Interesting Sam. Thanks.

 

Check out this link. Lord of the Flies did a cheaper way of dampening with good results. http://nemini.org/Forums/viewtopic/t=3426.html

- Dan