Quiet Exhaust

shawn

shawn

running dog lackey of the oppressor class
Administrator
Joined
Mar 13, 2005
Location
Raleigh, NC
Where's the quiet exhaust tech? I've done the straight pipe thing. That's fun around town, but sucks after an hour or two on the interstate.

So about a year ago, I did a full 4" pipe with a big Nelson (or Donaldson?) muffler. It's a straight-through, about 40" long and 10-12" diameter. Much quieter all around, except for towing.

I think there are two separate issues at work:

There's a lot of noise coming out of the end of the pipe. If I get up alongside another car or a jersey wall or something, it echos back against the truck. That's not a issue in and of itself, except that my trailer is a gooseneck enclosed trailer, and I think the trailer catches some of the noise and reflects it back at the cab. I'm wondering if a turn-down tip would help... maybe point it down and back, so it can't easily reflect off anything else.

There's some resonation/echo within the pipe itself. Has anyone experimented with muffler placement to see if it makes a difference? Maybe move the muffler closer up to the downpipe, etc. I have another short straight-through muffler (~24"?) that I could install right off of the downpipe, see if that kills some of the initial noise, then have a short section of pipe into the big muffler. It's still all straight-through, so I wouldn't think there would be a backpressure issue, but it might increase turbulence in the exhaust stream.

The other option is to gut the interior and install a bunch of sound deadener...

Thoughts?
 
What kind of truck? Cummins? Duramax? Powerstroke?

In my experience, Cummins just tended to be a louder in the cab no matter what, at least the 2nd gens I have been around...

I see a few options.
1. Take a different approach, apply more sound deadening to the cab, rather than quieting the exhaust. The exhaust will sound quieter inside, you will have less road/engine noise, the cab will stay warmer in the winter/cooler in the summer, and you'd be surprised at how much better even a stock sound system sounds with the road noise deadened.

2. Add a straight through resonator...something slim and straight through. When I had my exhaust exiting in front of the rear tire, I had no room for a normal muffler, I was able to fit this Aeroturbine 4040xl on the front pipe, where the catalytic converter would have gone on a newer model truck, it actually did a great job at getting 75% of the drone gone, while still having an aggressive exhaust note. Something similar would likely help to quieten you down without restricting flow too much. The "XL" series had a "turbine" muffler and a resonator built in.
http://i44.photobucket.com/albums/f43/GCncsuHD/dmax/DSCN2728.jpg
http://i44.photobucket.com/albums/f43/GCncsuHD/dmax/DSCN2731.jpg

3. While it wouldn't help the sound bouncing off of cars, mountains, the trailer, etc., there is some truth to the length of pipe after the muffler affecting the frequency of the resonance due to the relation of length of the wavelength and frequency of the exhaust pulses to the length of pipe. By moving the muffler forward/backward you can change the RPM range where you would hear the drone. There was an interesting article I read about this a while back, that even included nifty devices people made to alter the drone RPM using expansion chambers off the side of the exhaust, much like you see on the stock intake tubes. It works on the same principle as blowing on the half empty drink bottle, using that resonance to cancel out the other.

4. How is your exhaust exiting currently? As you mentioned, turning it down to focus it away from the trailer and other vehicles would help greatly.
 
Resonation can actually be aused y oo little back pressue also as counter-intuitive as that may seem. I will whole heartedly echo the sentiments on #1 by the wolfie fan above. Someone (Rich maybe?) years ago actually did a nice write up on a 2-3 hour $200 Dodge crew cab insulation solution using convention construction materials.

The CTD is not a super quiet engine to be sure, but the Box it is in is a noisy bitch.
 
It's a 3rd gen Dodge. 03 w/no emissions equipment. Right now, it's 4" thin-wall downpipe (not the stock heavy wall stuff) into about 4' of straight tube at the transmission, then the muffler, immediate up/over the rear axle and then square turn-out behind the tire.

What was the secret sauce on sound deadening? There's just regular Home Depot bituthene sheets... which are thick, but probably not as thick as some of the 'premium' purpose-built sheets.
 
Ron said:
The CTD is not a super quiet engine to be sure, but the Box it is in is a noisy bitch.
Click to expand...

Honestly.... if it weren't for Sara, I probably wouldn't care. I'd just turn the radio up a bit and roll on. Empty, it's the quietest vehicle I've ever owned. I think it's got less road noise than the Explorer, and there's no diesel rattle once you get off idle. The problem is rolling down the interstate late at night w/the trailer... and then wanting to listen to the radio w/o waking the baby. ;)
 
I'll be watching this thread because my truck is going to need a new exhaust system some time in the next year or two, and I want a VERY quiet exhaust.
 
We install Hush Mat on a regular basis in our customer's vehicles. It helps, but it dosent kill it all together. I called thier tech line and spoke to the acoustical engineer. He said the remaining noise issue is the fact that the auto makers keep putting thinner and thinner glass in the cars. I figured he was full of :poop: untill, low and behold, Honda started offering a optional "Quiet" windshield in thier high end stuff. We ordered one and it was like night and day difference. Take it for what its worth. :shaking:
 
I followed Rich's install of the "asphalted butyl" flashing in his truck and it wasn't bad the one time I rode in it. It was cheap & impressive enough that I did the floor (firewall to hatch) in my Mustang (2.5" uncatted Bassani X-pipe into 2.5" MAC Flowpaths w/ full tailpipes = fawking LOUD) with "Peel & Seal". It's stoopid simple to install and while I don't the equipment to measure the db's, it made a huge difference in both sound, resonance, & drone (didn't kill it 100%, sure knocked the edge off!). Both HD/sLowes carry the 6" wide rolls, but you can order larger 18" wide rolls.

If that doesn't totally do it for you, look into "1/4 wave" filters. They've been used for years to combat intake noise (aka intake "appendage" on all the Vortex's) and used in industrial apps (deadend T's) to quieten & kill drone. Planning this route to put a stop to my 2000 rpm drone once & for all...

There are mega threads on both the Peel&Seal and the 1/4 wave filters on the Corral.com in the General Tech forum.
 
JC rode with us on Saturday while towing the enclosed trailer. He said my diesel Dodge was quieter than his V10 Dodge. :lol:
 
I've always recommended corsa drone buster for cr trucks. You still get that deeper tone and great airflow but you eliminate the headache causing drone.

Sent from my DROID BIONIC using Tapatalk
 
Shawn said:
JC rode with us on Saturday while towing the enclosed trailer. He said my diesel Dodge was quieter than his V10 Dodge. :lol:
Click to expand...


I think tires may play a role here......
 
Shawn, we just got back off of a 1800 mile trip. I run a 5in exhaust with no muffler from a 400 Caterpillar. When I did the straight swap, I turned the turn down out to the side at a 45% angle to keep a little heat off of the right front tire of our flat towed car. The noise was terrible! While into our trip we loosened and turned the turnout straight down and this made a big difference. I was shocked at how much quieter it was. Temp on the tire went up about 40 degrees but I can live with that. A friend of mine has the exact same setup as mine and has kept diligent fuel mileage records since 2005 and with the straight pipe setup versus a Aero 5050XL muffler, the Aero muffler he gains .3 miles per gallon! I will be ordering me the Aero muffler very soon, also mellows out the bark of the sound. Ebay has the Aero for $140.00 delivered with a 5in. inlet and 5in. outlet. 4inch is also available.
 
I think preventing the noise from exiting the pipe is your #1 goal, followed by sound deadening as #2. (the deadening really has no drawback other than your time)

HDG's info just above is interesting.. and likely worth following. (damn, I hate it when he's right)
 
Rich, did you do the floor and rear wall? Floor, rear wall and doors? Floor only? I remember seeing pictures of the floor, but don't remember how much further you went with it.
 
there is a 53" donaldson you can install that might help with the noise.


I have a 40" donaldson and I have similar drone while towing. Its not bad.
 
Rich said:
I think preventing the noise from exiting the pipe is your #1 goal, followed by sound deadening as #2. (the deadening really has no drawback other than your time)

HDG's info just above is interesting.. and likely worth following. (damn, I hate it when he's right)
Click to expand...
Heh Heh Heh!
 
Shawn, the 30" FTE resonator made a big difference on my Dodge. The closer you get the resonator to the engine, the less droning/noise you will get. I would put that inline with your existing system. If it's still too noisy then go for the sound proofing.

I'm only running the 30" FTE resonator on mine and I have it just after the bend in the down pipe. Works well, but I think I would benefit from a muffler and some dampening. The cab of the truck still vibrates more than I'd like.
 
i did the whole inside of the k5 will peel and seal. i don't know how loud it would be without it but i do know it's a whole lot cheaper than dyno-mat. it was super easy to put down and contoured very well. i also bought a few rolls of the aluminium tape to cover the seams so the tar(sticky crap) didn't seep through after it got hot a few times.



ai218.photobucket.com_albums_cc317_putzarerequired_blazer_20build_IMG_0292_1.jpg
 
transman, where did you get that stuff? Price?
 
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