New exhaust = Loud drone at 1200-2000 rpm when accelerating

**v8a6** · 01-19-2012 11:27 PM

I finally got my exhaust pieces installed:

Miltek catless 2.5 inch downpipes
Magnaflow 16493 catback (without the tips) 2.5 inch and includes resonators
Dual Magnaflow 59926 Catalytic Converters welded in
a pair of exhaust tips I got off ebay

The exhaust sounds very good, except in the 1200-2000 rpm range where, under throttle, it exhibits loud drone that fills the inside of the car with sound. I am sure from the outside it sounds awesome, but from inside you cant hear the radio or people speaking. My main concern is that, over time, the loud drone could cause hearing damage to my 1-year old daughter in the back seat.

What is the best way to eliminate the drone, while not decreasing performance? While the sound is awesome at higher RPMs, I would sacrifice that if necessary to quiet the lower RPM drone.

I couldnt get a good pic at night, but thought Id include one anyway...

**speedydragon** · 01-20-2012 12:49 AM

12 or 14in resonator right in the middle of the setup should cancel out all the drone

**G Men 08** · 01-20-2012 01:20 AM

I have heard an x pipe in the middle will help. Look up the custom exhaust thread

I remember how bad my v8 was after the exhaust setup. Loved it when under throttle, but crusing down the highway, i wanted to take a hard right.

**v8a6** · 01-20-2012 06:06 AM

Thanks for the tips. Only problem is that the Magnaflow 16493 kit that is installed already runs two 4x14 inch resonators and has a x-pipe in the middle

Full specs
http://www.magnaflow.com/02product/d...rtnumber=16493

I have read that I may be able to put a couple T-pipes which dead end near the rear of the exhaust. The length of each should be determined by the frequency that needs to be eliminated. Has anyone tried this?

**speedydragon** · 01-20-2012 02:01 PM

If that's the case, then it's probably your miltek piggies.

**quickglx** · 01-20-2012 06:40 PM

subscribed...

I have the same cat back exhaust but with stock downpipes/cats and the same issue with my S6. Love the sound above 2k rpm... Under that though it takes a very very light throttle to maintain sanity. I've decided that when the kids are in the car I just keep it in sport mode to keep the rpms higher. I really don't want to put the stock exhaust back on.......

**Avi'sA6** · 01-20-2012 08:23 PM

Try using some kind of sound deadening insulation. Something like Dynomat, Boom Mat (eBay is your best bet). What you want to do is layer it in the trunk and underneath the rear seat. That will lessen the drone in the cabin but keep your exhaust note where it is outside.

**quickglx** · 01-20-2012 09:12 PM

^ I plan on doing something similar, but from my experience in my S4 the results are limited. The frequency is just too low to effectively block. What you want to do is use a sound deadner to dampen large panels, but this will have little to no effect on the exhaust noise. Then you need a thick, heavy material suspended from the body, continuosly applied. Even then it will be a smaller than needed change. In the OPs sedan, you could isolate the trunk- create a barrier on the back seat and the rear shelf under the window and the trunk floor. this isn't an option in my wagon tho... Sound dampening/blocking will be heavy and time consuming as well as only slightly effective, but it is a start. I'd prefer to do a modification to the exhaust to change just the resonances below 2k rpm. For me its just a tad too much. Now its impossible to pull into the driveway unnoticed, as any more than light throttle becomes boomy and mildly obnoxious. To my neighbors it probably sounds like my muffler fell off at the bottom of the hill

**redge2.7t** · 01-20-2012 10:35 PM

An xpipe helped tremendously with my droning. Do that with the dynomat or other sound deadening material (I did this as well) and you should be good to go. I have no drone with 2.5" piping with an xpipe, piggies, and magnaflow mufflers( no cats or resonators.

**v8a6** · 01-20-2012 11:31 PM

Thanks for all the replies.

quickglx, I think that your setup is the most close to mine, with the 4.2 engine and piggies. So it makes sense that we are seeing the same issue. I am wondering if this is why Magnaflow lists the 16493 for the 2.7, and not the 4.2.

Regardless, I am going to research a few more options:

1 - T-pipe (Helmholtz?) like in the pic below
2 - Different mufflers
3 - Different resonators (or additional ones)

**G Men 08** · 01-21-2012 01:48 AM

Stuff your trunk full of pillows and blankets to see if that helps. I did it with my v8 for investigative purposes and it actually helps a lot. I only had a few in there as well.

**v8a6** · 01-21-2012 07:16 AM

Originally Posted by G Men 08

Stuff your trunk full of pillows and blankets to see if that helps. I did it with my v8 for investigative purposes and it actually helps a lot. I only had a few in there as well.

Great tip! Ill try it out.

**beemercer** · 01-21-2012 01:00 PM

the full catless downpipes on the V8s tend to drone, headers help cut the drone out a lot but not really an option. Is it resonating the cabin when it starts to drone?

**v8a6** · 01-22-2012 04:28 PM

No, not really resonating in the cabin (as in shaking and rattling things). It is just very loud at the lower rpms, and then almost instantly dies down at around 2000rpm.

I have a feeling that the 16493 is just not 'muffling' enough since it was designed for the 2.7t with turbos, stock dps, and cats to pre-muffle the sound.

I really like the idea of the J-pipes that can be tuned to cancel out a specific frequency range. Just have to do some more research to see if it is worth the experiment.

**Avi'sA6** · 01-22-2012 04:41 PM

Originally Posted by G Men 08

Stuff your trunk full of pillows and blankets to see if that helps. I did it with my v8 for investigative purposes and it actually helps a lot. I only had a few in there as well.

this is exactly what i was going to say

Also more pictures of the quad tips im looking to do that soon!

**v8a6** · 01-25-2012 03:30 PM

Hey 01, I snap some more pics of the quad tips as soon as I have a chance.

Tried stuffing the trunk with a duvet today. Didnt help at all. Im going to stuff more in there to see if it makes a difference.