Read this...
https://www.asme.org/topics-resources/content/shrinking-exhaust-resonator-new-automotive-design
And check out these pics...
It appears that they add 1, 2 or 3 depending on the engine.
Anyone have one of these on their Silverado or Denali? 2018> I believe.
Well, that's cool.
That's cool...thanks for the link!
Done right in aftermarket applications, this could save tracks from noise issues.
I wonder if/when those will be available to buy, seems like a great technology
My guess is the best place to find them (for now) is on the floor of exhaust shops after someone has had a cat-back system added. Or wrecking yards.
I'm on the prowl already.
It does appear that these are used in the rear of the vehicles and the pipe seems large too. It will be interesting to see how easy it can be adapted to 2.25" or 2.5" pipe.
Maybe we'll start to see these on other models???
classicJackets (FS) said:I wonder if/when those will be available to buy, seems like a great technology
Reading between the lines, it sounds like you could fabricate one next week if you ordered from the right places tomorrow.
Strob’s team switched to a high quality stainless steel, but it had twice the thermal expansion rate of the ferritic exhaust pipe. Their design ultimately sandwiched the stainless screen inside a ferritic frame that attached to the exhaust pipe. This enabled the screen to expand and contract within without pulling free from the pipe.
It proved surprisingly easy to source the screen. The food industry has been using microperforated screens as filters for decades, and knows how to make them to order.
It would be really interesting to see the db reduction these accomplish. I wonder how they hold up over time with the probable build up of deposits on the interior surface.
In reply to MrJoshua :
I had longevity concerns when first reading over it, but then thinking that it's a factory exhaust component and the required minimum federal warranty period for exhaust components made me think that it must be pretty stout.
I don't believe it's for sound reduction. It's to combat resonance (drone) in the pipe and therefore in the truck cab.
There is a video on YouTube of some dumbass doing a video sound clip with and without the resonators covered with tape. The stock one he standing behind the truck. With them taped over he driving around?
WTF? How the hell can one compare that? I hate stupid people....
This is extremely relevant to my needs. If anyone finds these and grabs a few, I'd love to pay some $$ for the trouble. My 62 Midget project would benefit greatly, as I have very close to zero room.
So it looks like it is location dependent:
This doesn't appear to be a new technology if OEMs like GM have already adopted it on some road vehicles. It would be interesting to see if this would hold up in a racing environment or even more severe applications like rotary engine exhausts where killing high frequency noise is essential.
EDIT: Ran outside and looked under my 2019 Silverado. Sure enough, there are three of these on each tailpipe just forward of the tips.
This is a cool technology, but I can't help but wonder how quickly they get packed full of carbon buildup. I wonder if we'll see a TSB from GM about blasting these with carb cleaner and compressed air to reduce exhaust noise...
I bet a rotary motor would reduce that to tin foil confetti!
In reply to bentwrench :
That was my initial thought as well. Especially the part that said they start with 0.3 mm SS!
“It’s a mechanical process,” Strob said. “We start with a coil of stainless steel 0.3 mm thick and 300 mm wide. A press with a tool that looks like a lot of rectangular knives drops down and cuts slits into the coil. This bends the coil, which gets stretched lengthwise to open the slit geometry and pressed down again flat.”
That's 0.012 in! They also don't mention they type of SS used. Even 321 SS probably wouldn't survive too long at that thickness. Perhaps a Ni alloy like Inconel 625 might work but I have no idea if it's even possible to perforated IN626 sheet.
So the holes are big enough for the sound waves to escape, but too small for exhaust gasses to pass through? There's some pretty clever people out there.
I wonder if it actually sucks air into the exhaust, like a faucet aspirator vacuum fitting.
In reply to thatsnowinnebago :
I'm picturing a massive exhaust leak when they let go. Sounds great, but for how many miles?
In reply to thatsnowinnebago :
Basically sized just large enough to release sound energy but also small enough that aerodynamic friction prevents gases from escaping. Many people don't realize just how bad mesh is for airflow. Outside of the general blockage (% open area) fluid flow around smooth cylinders is poor. Boundary layer separation leads to increased drag, which slows flow and in the case of an orifice can block flow. I'd be willing to bet there is a bit of gas escaping at low exhaust velocities but that doesn't matter since energy/temperature is small.
In reply to Vajingo :
My truck only has 4000 miles on it but seeing as they've been installed in trucks since at least 2018 I imagine there are plenty out there with some miles on them. Regardless, they aren't for sound level reduction but frequency tuning. Aside from the catalytic converters in the exhaust manifolds and downpipes my truck literally has one large muffler in the middle. A single pipe goes back just past the rear axle that splits into two with each having three of these "resonators." They're located just upstream of the exhaust tips so even if they blow out I doubt it'd make a difference. There's already nothing behind them doing anything for sound. Maybe a slight change in frequency because the length of the exhaust will be shortened slightly.
I have to think the location could be calculated using Helmholtz resonance models. I'm looking at my Ram 2500 with 4" exhaust wondering if I can rid it of its drone on the highway.
Looks like 50%, 62.5% and 75% of tailpipe length is the appropriate location
It looks like the dB reduction is at the resonance frequencies without much change everywhere else.
In reply to MrJoshua :
Man, I book marked that so hard!
Pretty cool stuff..
Thanks for sharing. I just added a14×4 resonator to my project to attenuate the bag of wasps exhaust tone at 3k rpm.
These little plates are nice and small comparatively.
Greg
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