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Re: Making a muffler
Posted: Sat Nov 25, 2017 2:09 pm
by ptuomov
Coated manifold and downpipes are back, this is getting closer to being fired up again. It’ll be interesting to see and hear whether we’ve improved both the sound and back pressure.
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Re: Making a muffler
Posted: Sat Dec 02, 2017 4:33 pm
by ptuomov
John Kuhn is running the pipes to the rear now. The inconel bellows on one of the legs is maybe a bit of overkill, but better safe than sorry with the thermal expansion and contraction causing havoc in the rear muffler...
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Re: Making a muffler
Posted: Sat Dec 02, 2017 9:48 pm
by emsvitil
What does a bellows do to exhaust flow?
I would think that it would cause some turbulence and back pressure.....
Re: Making a muffler
Posted: Sun Dec 03, 2017 11:37 am
by ptuomov
emsvitil wrote: ↑Sat Dec 02, 2017 9:48 pm
What does a bellows do to exhaust flow? I would think that it would cause some turbulence and back pressure.....
There are different designs as far as the inside surface goes. Some even have three layers, a weaved outside cover, the expansion shape in the middle, and interlocking rings on the inside. Some are going to flow better than others. We're currently using two-layer ones, without the outside weaved cover but with smooth inside flow path.
Can I get some action from the back section (Re: Making a muffler
Posted: Sun Dec 03, 2017 12:03 pm
by ptuomov
So this is close to ready. I really like the looks. It’s also pretty clear that nothing bigger will fit behind the rear axle:
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Re: Making a muffler
Posted: Sun Dec 03, 2017 3:26 pm
by pdq67
I hope I didn't pi*s anybody off...
So how is this thread doing?
pdq67
Re: Making a muffler
Posted: Sun Dec 17, 2017 11:55 am
by ptuomov
Re: Making a muffler
Posted: Sun Dec 31, 2017 7:33 am
by In-Tech
It looks good. I am interested how this project turns out.
The Borla XR1 had a good concept doing what later catalytic "high flow" convertors did using honeycomb in the substrate design.
You poked fun at the large outlet and concerns of children and animals getting in there.
I wonder if some stainless honeycomb might be a good solution at the end and will do a bit more of altering the tone.
http://www.honylite.com/stainless-steel ... cores.html
"Honeycomb placed in front of the fan increases the downstream velocity as a result of its ability to redirect the air in a straight path and reduce vortices.
A similar effect happens with ducted fans. Although the duct itself straightens or contains the air flow, honeycomb immediately in front of the fan aids in removing vortices and swirls in the flow.
Turbulence causes noise, particularly at high air velocities of 1500 – 4000 ft/min (457 – 1219 m/min). Straightening the air flow can be beneficial not only in reducing power requirements, but also in keeping down the noise."
Re: Making a muffler
Posted: Sun Dec 31, 2017 8:50 am
by j-c-c
On vortices in high speed air flow, I believe I have read the "crackling" sound in high speed turbine exhaust for example are small vortices breaking the sound barrier and causing thousands of mini sonic booms, I can fathom a smoother exhaust flow in our application would have benefits up to the point of increased surface friction
Re: Making a muffler
Posted: Mon Jan 01, 2018 5:20 pm
by ptuomov
In-Tech wrote: ↑Sun Dec 31, 2017 7:33 am
It looks good. I am interested how this project turns out.
The Borla XR1 had a good concept doing what later catalytic "high flow" convertors did using honeycomb in the substrate design.
You poked fun at the large outlet and concerns of children and animals getting in there.
I wonder if some stainless honeycomb might be a good solution at the end and will do a bit more of altering the tone.
http://www.honylite.com/stainless-steel ... cores.html
"Honeycomb placed in front of the fan increases the downstream velocity as a result of its ability to redirect the air in a straight path and reduce vortices.
A similar effect happens with ducted fans. Although the duct itself straightens or contains the air flow, honeycomb immediately in front of the fan aids in removing vortices and swirls in the flow.
Turbulence causes noise, particularly at high air velocities of 1500 – 4000 ft/min (457 – 1219 m/min). Straightening the air flow can be beneficial not only in reducing power requirements, but also in keeping down the noise."
John is about six welds and assembly away from firing up the car. We’ll see and hear soon how it worked out.
Unfortunately, there are no XR-1 multi core mufflers that fit my available space well. I think the concept makes sense.
The self generated noise from the flow is most significant when the exhaust flow velocity is high and temperature differences are the largest. Therefore, upstream mufflers usually generate more of it. That’s why the tail pipe muffler is absorptive, absorptive muffler should clean up the flow generated noise frequencies nicely.
Stainless steel honeycomb might be something to try at the tailpipe if we can hear some problem frequencies that come from flow.
Re: Making a muffler
Posted: Sun Jan 07, 2018 7:24 am
by ptuomov
naukkis79 wrote: ↑Sun Oct 08, 2017 1:26 pm
That infinity pipe probably creates big turbulences and flows very badly, it's shape is extremely anti-flow like.
Look at the poor fools designing F1 exhaust ports and headers. The idiots are using the same “anti-flow” infinity-pipe shape off the head in their exhaust. Fail!
https://youtu.be/Q9X-Xe3ueL0
Re: Making a muffler
Posted: Sun Jan 07, 2018 7:42 am
by hoffman900
ptuomov wrote: ↑Sun Jan 07, 2018 7:24 am
naukkis79 wrote: ↑Sun Oct 08, 2017 1:26 pm
That infinity pipe probably creates big turbulences and flows very badly, it's shape is extremely anti-flow like.
Look at the poor fools designing F1 exhaust ports and headers. The idiots are using the same “anti-flow” infinity-pipe shape off the head in their exhaust. Fail!
https://youtu.be/Q9X-Xe3ueL0
I see the exhaust port continuing it’s transition from a 4 valve with a divider to a round pipe. If anything, the transition is likely seamless.
Re: Making a muffler
Posted: Sun Jan 07, 2018 8:21 am
by ptuomov
hoffman900 wrote: ↑Sun Jan 07, 2018 7:42 am
ptuomov wrote: ↑Sun Jan 07, 2018 7:24 am
naukkis79 wrote: ↑Sun Oct 08, 2017 1:26 pm
That infinity pipe probably creates big turbulences and flows very badly, it's shape is extremely anti-flow like.
Look at the poor fools designing F1 exhaust ports and headers. The idiots are using the same “anti-flow” infinity-pipe shape off the head in their exhaust. Fail!
https://youtu.be/Q9X-Xe3ueL0
I see the exhaust port continuing it’s transition from a 4 valve with a divider to a round pipe. If anything, the transition is likely seamless.
Yeah...
Re: Making a muffler
Posted: Sun Jan 21, 2018 1:00 pm
by ptuomov
The exhaust is about done, John Kuhn is putting the finishing touches on it:
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Still no sound check!
Posted: Tue Feb 06, 2018 10:11 pm
by ptuomov
But at least the muffler now shines:
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