I installed a while back a Borla exhaust and love the way it sounds on the outside but the inside is another story. This is sort of a one hour car in that after an hour of driving nonstop it is very tedious and wearing as well. In my mind it has to be due to the SMT panels flexing with the lounder exhaust acting like you are sitting inside one big speaker. If you put quiet mufflers on you lose the sound outside and inside as well because I think you have less enegy to make the panels vibrate. Also it is much better running 2500 in third that 1700 in 4'th (A4 trans in a 91 coupe). I have looked on the web and done some searches here for sound damper or sound deadening with a small amount of luck but did not find anything that looked like a good fix. Any ideas for something that really works and does not cost a fortune to install. I will provide the labor over the winter...
Dave

 

id go for something like this, it works, but i dont know if that company is cheaper then others, so look around

http://www.all-car-carpets.com.au/pa...word//offset/0

 

Antbody ever try this stuff??
http://www.secondskinaudio.com/vibra...p?category=120

 

so sad yet again ... buy the good stuff and have it be too noisy.... had to deal with it even with the Corsa's I tried the dynamat clone and the radio soulds better but no, it did not work for the reverberation....drone, groan, resonance, loadness, decibels, what ever you want to call unwanted noise.....

 

When I replaced the exhaust I used a rear crossover pipe and I have no drone at cruising speeds can talk normal and listen to music without high volume. But when I get on it, it sounds great

 

So you welded a pipe between the left and right side I am quessing in front of the spare tire carrier? Like this?
http://www.ecklers.com/product.asp?p...4&dept_id=1333

If so seems like a very simple fix.. Something to do before winter

 

describe your exhaust setup completely please

 

87 L98 precats removed, full flow cat, Walker rear Y pipe with cross over tube & heat shields, Mid America ZR-1 Style Exhaust. Flows good, sounds great. Not much more to say.

 

I would certainly like to know as well.

Went for a couple hour cruise this afternoon with some specific goals in mind. One to have a good lunch at a place out in the country second was to think about the drone issue. i put my hand on the floor right behind the front pass side seat while driving. When the drone starts the floor is physically vibrating and shaking the more pressure on the throttle without changing rpm , TC locked and OD going up a grade makes more drone and vibration on the floor slightly releasing throttle pressure and 90% of it goes away as will a downshift to third and a bit more rpm make most of it go away. I don't think it is the exhaust systems true fault because the whole rear floor assmbly is vibrating and being a sounding board. I think the original problem is GM's design problem not Borla magna flow or any of them as the majority of dron is in 1980's and 90's cars from what I have found on the web but certainly willing to be corrected as long as some documentation of many cases can be sited with late model cars. I think the free flowing exhaust is just providing more energy to make the panels vibrate. From some playing around with a calculator i am thinking the range of frequencies is between 20 to 40 Hz centered at 30 Hz (1800 RPM). My reason for this thought /explaination is because if I forced a downshift and more rpm the vibration went away at least 70% and got a rather pleasant muscle car sound of a engine accelerating and while a bit loud not nearly as annoying and actually easier to hear the radio and talk.

I would certainly welcome any and all comment and testing by others. Ideally someone with a small friend the could ride in the back of a coupe on a deserted safe road and just feel around as to what is shaking the most is one idea though their mass in the back might make that test provide info that is useless as from what i have read is adding mass damps the vibration. Now that I think about it I have driven thogh nopt competitivly NASCAR modified stock cars mainly on and off old schooltrailer and haulers or arcoss a parking lot from one part of a shop to another though decades ago and every piece of sheet metal was vibrating making a racket inside the car. Personally I think this is a solveable problem with some simple measures to stiffen up the SMT panels. I can envision truck bedliner painted both under the car and inside the trunk, indise the pass side storage compartment alnog with some heavery damping material, the same insdide the cavities for rear speakers and possibly some spray expanding foam as well in the corners to make the free panels smaller. Open to lads of well thought out ideas here to make this issue go away!

Again sorry for the long post though I gave this more than casual thought.. and engineer's reason to not sleep often..LOL..

 

yeah you diagnose the prob, i dyamatted the rears only, since it was such a PITA

 

Dose anyone have a borla exhaust on their 328i if so how much did you pay, is it custom, and are you happy with it? Please just let me know im thinking about getting one.

This is what they quoted me on the website.
__________________
La mutuelle familiale de France
Devis mutuelle familiale des cheminots fr

 

a 328i? not many BMW owners are going to be replying in this thread. may want to try a BMW specific forum...

 

a couple of?s was your borla a full cat back system or just the mufflers ?did you change anything else up front of the borla system ie cats headers etc?

 

No precats now has 2 1/2 Y pipe stainless bought it used off a member here in very nice condition

Magnaflo cat old one looked pretty beat up and one of the precats had a rattle so thought that a good idea as all the cats were the same age and milage.

Borla cat back system pipes and mufflers