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The cure for your exhaust drone

the TURD

NAXJA Forum User
Location
SE Michigan
Recently I redid my exhaust system, and found that it droned terribly between about 2600-2900 RPM. It was miserable to drive and I felt like an idiot teenager driving around. So I figured I'd try a something I'd read about called a 1/4 wave resonator.

It's basically a capped pipe that tees into your exhaust pipe, and what it does is cancels noise waves by sending an equal and opposite wave back into the exhaust pipe. The exact frequency it targets is based on the length as well as the chemical characteristics and temperature of air inside the pipe.

DSC_1909.JPG


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This is what mine looks like.

As you can see, it's pretty simple to build and install. I made mine about 30" long and it worked wonders. The average sound level in the drone area was reduced by 11 dB, which is a 10x reduction in sound energy.

If you want more details, visit my blog: http://ironhydroxide.blogspot.com/2017/09/drone-warfare.html
Sorry, I just didn't feel like typing everything twice.

BTW, if you are wondering what my exhaust sounds like, this is it:

https://youtu.be/ArbPoxbWSog
 
Very interesting solution ! Cool!

It seems to me that a nice welded muffler with a couple of chambers would have solved your problem, reduced db level across the range, and have been NP/NF legal as a spark arrestor . But that's me. Everyone has a different vision as what they want their Jeep for :)
 
Drone isn't something you can necessarily hear from the outside of the vehicle, since it's an interaction between the body and the exhaust. The nice thing is it's not as loud inside as you would think because the drone is gone. Outside, the volume level is about the same as your standard aftermarket exhaust.

WB9YZU, what are the requirements for a spark arrestor? I rarely get to actually go wheel but I'd be surprised if it's an issue here (just barely moved to Michigan).
 
Spark arrestor requirements for Autos/Trucks/Jeeps are not seriously stringent.
Essentially, the muffler just has to trap a spark.

Here is the snippet from the NFS website.

During fire season (May 1 – Sept 30) all vehicles on NFS (National Forest System) lands must be equipped with a baffled muffler, serviceable tailpipe and should contain operable fire extinguisher (2.5 lb capacity, 4BC rating).

So basically, no straight through mufflers and no missing tail pipes.
That still leaves lots of options for a nice sounding performance exhaust system that won't rattle your teeth :)
 
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So basically, no straight through mufflers and no missing tail pipes.

So something like this? This is a picture of the inlet of my muffler. It looks the same in the outlet as well.

That still leaves lots of options for a nice sounding performance exhaust system that won't rattle your teeth

I'm not sure if you are inferring that my exhaust is really loud. I promise you it's not, at least on the inside, though without the quarter-wave resonator it was loud inside.
 
If that's like the normal glasspack, it's not a baffled muffler.
Baffles means that there is no straight-through path for things to pass through, to my knowledge. IE: you can't see straight through it.

That pic is as installed, correct? So the only reason we can't see through is that one end is closed off, visually.
 
BTW, how do you bend your pipe? I need to fabricate a crossover and I really don't want to use crimped bends (even though from a performance standpoint it won't make a difference).
 
BTW, how do you bend your pipe? I need to fabricate a crossover and I really don't want to use crimped bends (even though from a performance standpoint it won't make a difference).
Any quality muffler shop should be able to mandrel bend exhaust pipe. If not then Jegs or Summit will have pre bent pipe you can ordered.
For a relatively low rpm motor an H pipe would be better than a x. They make more power in the lower rpm's than an x does
 
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That's not what this is for. This is simply to get a V8 to exhaust through one muffler. Might seem wasteful or shortsighted, but there's only so much space under an S10, and I am moving the battery and tranny cooler (as well as a filter assembly) to the space a second exhaust unit would have to go if I went to duals.

EDIT: ALTHOUGH, now that this is mentioned, if I was able to squeeze a true dual exhaust into the package, it would simplify a great amount of the exhaust work by way of not having to deal with a collector to merge 2 into one.... and then I could put that H pipe to work with a couple simple fishmouth joints and a bit of welding time. Hmmmmmm...
 
Seems like it would be easier to run the exhaust outside the frame rails and dump it before the rear tire than to mess around with 2 into 1. But is been a very long time since i have been under the cab portion of an s10
 
It's actually an S10 Blazer, but quite similar to the pickup, with the added benefit that the fuel tank is behind the rear axle, giving more space.

Plus, I an running a 2" body lift (had to for tire clearance, and drivetrain clearance since I pushed the powerpack 2" aft), so I could very easily stand the mufflers on end.

Now that you have me thinking outside the box, so to speak, this may not be terribly difficult. Hell, I may be able to run the second pipe alongside the first and have just a 6" H-pipe betwixt them. Buy a second tailpipe the same as the 4.3 stock size, which was going to stifle the V8... but if I am only exhausting the one bank out of it, it's a non-issue.

Heck, weld flatbar between the pipes, and I can even use the factory hangers.

You have me thinking outside the box now, and I believe you've solved my problem!
 
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I alkso like how you've replaced the manifold flange with a v-band flange. I may do that in this application as well, as it's not sealing well (89 lo-po Camaro flanges. There is literally no gaasket, and red RTV hasn't done the job. I'm tired of exhaust leaks!
 
Any quality muffler shop should be able to mandrel bend exhaust pipe. If not then Jegs or Summit will have pre bent pipe you can ordered.

I have yet to see an exhaust shop with a mandrel bender. All that I have ever seen are press benders.

A mandrel bender takes up nearly as much floor space as an automobile.

Here is an example of what a mandrel bender looks like:

https://www.youtube.com/watch?v=gdtrTaY7yfk

That long bar that runs the length of the machine is the support for the mandrel. Around the 40 to 45 second mark you can get a decent sense of the mandrel itself. It is comprised of several jointed segments which are able to follow the bend and support the pipe from the inside.

I cannot see a mandrel bender making sense for an exhaust shop. Just the time to change over the tooling from one tube diameter/bend radius to another would be prohibitive, never mind the setup time to go between patterns.
 
If that's like the normal glasspack, it's not a baffled muffler.
Baffles means that there is no straight-through path for things to pass through, to my knowledge. IE: you can't see straight through it.

That pic is as installed, correct? So the only reason we can't see through is that one end is closed off, visually.

No, it's not a glasspack. It's a Flowmaster Hushpower. I had a glasspack on it previously and it was way too loud.

This is not installed, and the reason you can't see through it is because you are looking into a perforated cone, and there is one in each side of the muffler.

274721d1199612809-best-muffler-custom-exhaust-size-hushpower.jpg


hushpower_images_grande.jpg



BTW, how do you bend your pipe? I need to fabricate a crossover and I really don't want to use crimped bends (even though from a performance standpoint it won't make a difference)

I get my bends from Columbia River Mandrel Bending. They are consistently the best prices I've found. http://www.mandrelbends.com/
 
I have yet to see an exhaust shop with a mandrel bender. All that I have ever seen are press benders.

A mandrel bender takes up nearly as much floor space as an automobile.

Here is an example of what a mandrel bender looks like:

https://www.youtube.com/watch?v=gdtrTaY7yfk

That long bar that runs the length of the machine is the support for the mandrel. Around the 40 to 45 second mark you can get a decent sense of the mandrel itself. It is comprised of several jointed segments which are able to follow the bend and support the pipe from the inside.

I cannot see a mandrel bender making sense for an exhaust shop. Just the time to change over the tooling from one tube diameter/bend radius to another would be prohibitive, never mind the setup time to go between patterns.

This has been my experience as well.

Looks like I'm off to Summit!
 
No, it's not a glasspack. It's a Flowmaster Hushpower. I had a glasspack on it previously and it was way too loud.

This is not installed, and the reason you can't see through it is because you are looking into a perforated cone, and there is one in each side of the muffler.

274721d1199612809-best-muffler-custom-exhaust-size-hushpower.jpg


hushpower_images_grande.jpg



I get my bends from Columbia River Mandrel Bending. They are consistently the best prices I've found. http://www.mandrelbends.com/

GREAT info!

Your truck is a bit loud for my tastes (each their own, I'm old! :) ), but putting resonators (glasspacks work as well) upstream of the main muffler will reduce that.

I did some research a few months back about this sort of issue, there was some interesting stuff on youtube about getting a quality tone (quiet at cruise, with a WOT bark) with cheap parts-house pieces. I think it's time I start burning steel and see what I can do.
 
I have yet to see an exhaust shop with a mandrel bender. All that I have ever seen are press benders.
A mandrel bender takes up nearly as much floor space as an automobile.

Here is an example of what a mandrel bender looks like:

https://www.youtube.com/watch?v=gdtrTaY7yfk

That long bar that runs the length of the machine is the support for the mandrel. Around the 40 to 45 second mark you can get a decent sense of the mandrel itself. It is comprised of several jointed segments which are able to follow the bend and support the pipe from the inside.

I cannot see a mandrel bender making sense for an exhaust shop. Just the time to change over the tooling from one tube diameter/bend radius to another would be prohibitive, never mind the setup time to go between patterns.
I know of half a dozen shops within 50 miles of me that have mandrel benders.
Maybe i am just lucky to have that resource
 
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