Dust Buggy

That spot in the second video always gets me in the 4runner. Cruises through every other section of that trail, but I have to winch through that spot. Fun times!
 
Minor update:
Replumbed the crank case vent to positive crank case ventilation.
Got rid of the crank gases that were blowing up and over the hood into our faces. CA gas smells pretty bad venting out of the engine.
The vent catch can never had oil, only water that was stronger than skunk spray.
No effect on performance or idle but the smell is gone.
 
Next up is getting the exhaust a little quieter.
The drone on the buggy is insane. Has something to do with the roof and floor and exhaust tune and exit point. Its perfectly tuned to resonate and make your ears stop working. Its not loud or harsh, its just the perfect frequency drone.
Tried a 4" tip instead of the 3" turndown and that just made it deeper and got the axle hot.
Next up is a 3" ID x 4" OD x 6" Dynomax Race Bullet 24250 Exhaust Resonator.
Held it up to the tail pipe and it quieted it down a noticeable amount before it got too hot to hold with welding gloves.
Sounds promising.
 
This is just a theory that I still haven't gotten around to experimenting with myself, so who knows if it'd actually work in real life.

If you can determine what the main frequency is causing the drone you might be able to make it cancel itself. You'd basically weld an additional pipe or tube to your exhaust that would basically look like a bypass tube on a shock. The length of this tube would be 1/4 the wavelength of your drone frequency. So the sound enters the tube, travels down, bounces back and re enters the exhaust after traveling 1/2 wavelength, meaning that sound is 180* out of phase, which in theory would give you a perfect cancellation. The range of frequencies above and below your drone frequency that would also be somewhat canceled, but not completely is called the Q factor. The bigger the diameter of the tube/pipe, the smaller the Q value, which means a larger range of affected frequencies. So you'd see a wider dip on your frequency response with a bigger pipe, and a more narrow dip/larger Q value with a smaller pipe.

Sound is pretty cool. Two sources of the same sound at 90db each if perfectly in phase give you a 3db increase for a total volume of 93db. Those two sources 180* out of phase in theory would give you a 90db decrease and complete cancellation. This can be a much more powerful tool vs sound absorbing technologies, especially as the wavelengths get longer. It is basically an acoustic absorber.

If this idea interests you at all, I can link some real world applications of this idea, just on a smaller scale more related to speakers and audiophiles. A series of smaller tubes tuned to slightly different frequencies can also be used to target a specific range, and might be easier to package in a buggy.
 
Trevlaw said:
This is just a theory that I still haven't gotten around to experimenting with myself, so who knows if it'd actually work in real life.

If you can determine what the main frequency is causing the drone you might be able to make it cancel itself. You'd basically weld an additional pipe or tube to your exhaust that would basically look like a bypass tube on a shock. The length of this tube would be 1/4 the wavelength of your drone frequency. So the sound enters the tube, travels down, bounces back and re enters the exhaust after traveling 1/2 wavelength, meaning that sound is 180* out of phase, which in theory would give you a perfect cancellation. The range of frequencies above and below your drone frequency that would also be somewhat canceled, but not completely is called the Q factor. The bigger the diameter of the tube/pipe, the smaller the Q value, which means a larger range of affected frequencies. So you'd see a wider dip on your frequency response with a bigger pipe, and a more narrow dip/larger Q value with a smaller pipe.

Sound is pretty cool. Two sources of the same sound at 90db each if perfectly in phase give you a 3db increase for a total volume of 93db. Those two sources 180* out of phase in theory would give you a 90db decrease and complete cancellation. This can be a much more powerful tool vs sound absorbing technologies, especially as the wavelengths get longer. It is basically an acoustic absorber.

If this idea interests you at all, I can link some real world applications of this idea, just on a smaller scale more related to speakers and audiophiles. A series of smaller tubes tuned to slightly different frequencies can also be used to target a specific range, and might be easier to package in a buggy.
Click to expand...
This bot has the tech!

:flipoff2:
 
Trevlaw said:
This is just a theory that I still haven't gotten around to experimenting with myself, so who knows if it'd actually work in real life.

If you can determine what the main frequency is causing the drone you might be able to make it cancel itself. You'd basically weld an additional pipe or tube to your exhaust that would basically look like a bypass tube on a shock. The length of this tube would be 1/4 the wavelength of your drone frequency. So the sound enters the tube, travels down, bounces back and re enters the exhaust after traveling 1/2 wavelength, meaning that sound is 180* out of phase, which in theory would give you a perfect cancellation. The range of frequencies above and below your drone frequency that would also be somewhat canceled, but not completely is called the Q factor. The bigger the diameter of the tube/pipe, the smaller the Q value, which means a larger range of affected frequencies. So you'd see a wider dip on your frequency response with a bigger pipe, and a more narrow dip/larger Q value with a smaller pipe.

Sound is pretty cool. Two sources of the same sound at 90db each if perfectly in phase give you a 3db increase for a total volume of 93db. Those two sources 180* out of phase in theory would give you a 90db decrease and complete cancellation. This can be a much more powerful tool vs sound absorbing technologies, especially as the wavelengths get longer. It is basically an acoustic absorber.

If this idea interests you at all, I can link some real world applications of this idea, just on a smaller scale more related to speakers and audiophiles. A series of smaller tubes tuned to slightly different frequencies can also be used to target a specific range, and might be easier to package in a buggy.
Click to expand...

this made me think of this exhaust, i think there are raptors kits that have this on them as well.
1760131547622.png


1760131646482.png
 
I wonder if you could do a telescoping tube setup with a clamp to dial in the frequency. I want to say there was something on youtube once where someone did just that and was able to tune their exhaust sound a bit.
 
mobil1syn said:
this made me think of this exhaust, i think there are raptors kits that have this on them as well.
1760131547622.png


1760131646482.png
Click to expand...
That's sick, yeah I'd imagine they're using the same principle or a combination of things.

I can't really see any reason why it wouldn't work to some degree, it's just physics lol. One day my exhaust is gonna have like 30 tubes running all up and down it while I'm in the back huffing exhaust holding my microphone up at the muffler lol.

If it did actually work and all you had to do was measure the drone frequency, add a couple 3/4" tubes and you could basically nuke the drone out of existence that'd be sick as hell. Just need like a $75 USB mic, REW(Room EQ Wizard(free software)) and you're rocking. Then after that you can use the mic to tune your stereo and pick up another expensive hobby...
 
Ghetto Fab. said:
I wonder if you could do a telescoping tube setup with a clamp to dial in the frequency. I want to say there was something on youtube once where someone did just that and was able to tune their exhaust sound a bit.
Click to expand...
Could definitely do that for testing and getting lengths dialed in, they do the same exact thing when building ported sub boxes. I'd probably make the final product a sealed tube though.

On a ported sub box, the port is basically functioning off of this same principle, except it's open at both ends and is shorter in length, so the sound coming out of the port is only partially out of phase, so you get some summation at the frequency the port is tuned too along with the sound coming out of the front side of the speaker.
 
Ghetto Fab. said:
I wonder if you could do a telescoping tube setup with a clamp to dial in the frequency. I want to say there was something on youtube once where someone did just that and was able to tune their exhaust sound a bit.
Click to expand...
Yea, you could play it like a trombone.
 
Helmholtz is under construction. Will update maybe this weekend if all goes well.

Meanwhile the import grade 3/4" universal joint on the steering column has a ton of play. That's what I get for using Amazon. The end caps are not tight on the cross so the axis has slop but the rotation is still good. So the steering wheel moves up and down and side to side as the cross slides in the caps and chatters but rotation is still tight with the bearings and cross.
Deciding if I should keep a u joint or switch to a different type of industrial joint. The steering column shaft only needs maybe 1 degree or less of misalignment to help out the orbital which is super sensitive to side loading of the input shaft. The joint needs to be weldable as I don't really want to buy a new splined orbital extension and a splined column shaft.
 
HYDRODYNAMIC said:
Helmholtz is under construction. Will update maybe this weekend if all goes well.

Meanwhile the import grade 3/4" universal joint on the steering column has a ton of play. That's what I get for using Amazon. The end caps are not tight on the cross so the axis has slop but the rotation is still good. So the steering wheel moves up and down and side to side as the cross slides in the caps and chatters but rotation is still tight with the bearings and cross.
Deciding if I should keep a u joint or switch to a different type of industrial joint. The steering column shaft only needs maybe 1 degree or less of misalignment to help out the orbital which is super sensitive to side loading of the input shaft. The joint needs to be weldable as I don't really want to buy a new splined orbital extension and a splined column shaft.
Click to expand...

Last time I ordered a universal weld-on joint for steering was from Howe, if you are looking for a non-Amazon vendor to order from
 
Siiick, curious to see how it turns out. What kind of dimensions are you looking at for it?

If you only need a small amount of misalignment on the joint, would a DIY rag joint work. Like the rubber split joints they used on the 70's jeep trucks steering gear and probably a lot of others too. Seems like you could fab up one of those with some pretty tight tolerances and it would last quite a while.
 
Ghetto Fab. said:
I wonder if you could do a telescoping tube setup with a clamp to dial in the frequency. I want to say there was something on youtube once where someone did just that and was able to tune their exhaust sound a bit.
Click to expand...
Isn’t that kinda what Supertrapp was, with the ability to add/remove discs?

The Fluid MotorUnion YouTube does cool exhaust work…but mainly to make them louder! A few videos talk about the megaphone they plumb into exhaust.

 
I tried the Helmholtz vs the bullet muffler resonator and it was night and day difference.
I used 3” tube for the 90° into the 3” chamber and then necked down to 2.5” for the outlet.
Thoughts were to create a chamber and slightly restrict the outlet so it wasn’t too free flowing where the noise would take the easy route out.
The P trap shape at the end was to direct the noise at an angle past the links and out to the side without hitting the links.
The 3” chamber is roughly 20” long.
The 2.5” tail is roughly 18” long.
The offset allowed the tail pipe to be longer as it cleared the links.

IMG_8815.jpeg

IMG_8811.jpeg

IMG_8817.jpeg

IMG_8818.jpeg

IMG_8824.jpeg
 
Pretty damn cool, that's awesome you actually had a noticeable difference. Rough math, but speed of sound is about 13,500 inches/second. Your chamber is 20" long, so it should be targeting the frequency with a half wavelength of about 40".

13500/80" = 169hz.

With 3" pipe I'd imagine your getting a fairly low Q value, so you've probably got some decent cancellation both above and below 169hz.

I wish you had a mic so you could get some before and after measurements. Be cool to see what the frequency response looks like.
 
Trevlaw said:
Pretty damn cool, that's awesome you actually had a noticeable difference. Rough math, but speed of sound is about 13,500 inches/second. Your chamber is 20" long, so it should be targeting the frequency with a half wavelength of about 40".

13500/80" = 169hz.

With 3" pipe I'd imagine your getting a fairly low Q value, so you've probably got some decent cancellation both above and below 169hz.

I wish you had a mic so you could get some before and after measurements. Be cool to see what the frequency response looks like.
Click to expand...
The speed of sound should be calculated at the temperature of the exhaust. At 400°F it's more like 17,200 in/second. At least that's what I read in my Farmers Almanac.
 
Firstram said:
The speed of sound should be calculated at the temperature of the exhaust. At 400°F it's more like 17,200 in/second. At least that's what I read in my Farmers Almanac.
Click to expand...
Ha, good catch! I hadn't thought of that, I don't usually push my speakers that hard lol
 
Had a chance to drive it around with the new tail pipe and while quieter, it doesn’t sound good. The pitch went higher.
I think it’s the 2.5” diameter being too small.
Did some research and a 6.0 should have a minimum 3” or dual 2.5” some had 3.5”.
The cross over and Y is 2.5” that jumps to 3” before the CAT and muffler. There is no room to make the Y 3” and I’m not sure it needs to be 3”. Maybe 2.5” is better to keep velocity up, IDK?
Going to replace the 2.5” tail with the 3” resonator muffler and see how it sounds.
 
Last edited:
Changed out the 2.5” tail pipe for 3” resonator and turndown and it brought back the deeper tone. Sounds a lot better. When rev’d up it quiets down and I don’t notice the drone. Haven’t had a chance to test on a long run at varying loads.

IMG_8894.jpeg

IMG_8893.jpeg
 
Last edited:
Deleted the u-joint from the steering shaft.
Removed the splined shaft from the orbital extension and turned down and welded to a longer shaft 1” OD 1/2” ID DOM. The splined shaft at the orbital has some slip so axial and angular allowance works with what is a nearly straight line from the orbital out to the bearing at the steering wheel. Steers fine and feels a lot better without the slop of the joint. Also extended the shaft another 2” to get it close to the seat for my boys.

IMG_8890.jpeg

IMG_8889.jpeg
 
i too did some playing around with exhaust last month and it is amazing what a resonator will do and what sound it removes. i was able to remove 20 DB with a differnt muffler and res combo and the sound is much better and we can talk in the cabin now. good job.
 
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