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Making a muffler

General engine tech -- Drag Racing to Circle Track

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Brian P
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Re: Making a muffler

Post by Brian P » Tue Apr 10, 2018 9:52 pm

That sounds really good. Nicely done.

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ptuomov
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Re: Making a muffler

Post by ptuomov » Wed Apr 11, 2018 7:02 am

Thank you for the comments.

The next steps on this are for John to button up the install and then drive the car around for bit. Next is tuning it on the dyno, and getting some back pressure data from the exhaust. Finally, a 1000 mile continuous test drive. I'll get some video and audio of the process.

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Re: Making a muffler

Post by ptuomov » Mon May 07, 2018 3:34 pm

The turbine outlet pressure is down from 2 psi to 1 psi, so 50% drop with less than 36% increase in the area. This is from debugging tests at about the same power levels (a hair under 700 rwhp).

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Re: Making a muffler

Post by ptuomov » Mon Jun 04, 2018 3:16 pm

The new exhaust is now sporting a bit of a tan, and and the system is making 2 psi of boost already at 1400 rpm:
8214B193-379C-416A-8079-FFAD879DD9BB.jpeg
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ptuomov
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Re: Making a muffler

Post by ptuomov » Wed Mar 13, 2019 9:32 am

This looks extremely interesting, if you're thinking about making racing mufflers:

https://www.eurekalert.org/pub_releases ... 030619.php

n2xlr8n
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Re: Making a muffler

Post by n2xlr8n » Thu Mar 14, 2019 8:37 am

ptuomov wrote:
Wed Mar 13, 2019 9:32 am
This looks extremely interesting, if you're thinking about making racing mufflers:

https://www.eurekalert.org/pub_releases ... 030619.php
I saw that on google news a few days ago. Good stuff.

I'd be interested to see how they make it withstand the heat from exhaust.
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Re: Making a muffler

Post by ChargerST » Thu Mar 14, 2019 10:22 am

I'd say for an exhaust pipe it could be 3D "printed" in metal (using a laser) and placed at the end of the exhaust pipe - heat is much lower there.

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Re: Making a muffler

Post by David Redszus » Tue May 21, 2019 8:04 pm

emsvitil wrote:
Fri Apr 21, 2017 7:13 pm
The termination boxes aren't mufflers (although they may quiet things a bit)

They're to fake out the exhaust system into thinking the headers open to atmosphere, rather than into a exhaust system...
Bingo!

The exhaust pipes should end at a certain tuned length from the head. This tuned length is far too short for most vehicles.

The trick is to insert a large diameter resonator at the proper distance, and then run free flowing pipes to the rear of the car.

I built such a system for a road racing BMW for a race at Road Atlanta. It easily passed the track noise limit but was very noisy inside the car. Sheet metal floors resonant quite a bit. Fastest car in class. But then it rained and the driver crapped his pants.

Prof Gordon Blais devotes an entire chapter to the design of noise cancellation exhaust plumbing in his Four Stroke book.
The required measurement inputs are:
Inlet insert diameter
Inlet insert length
Exit insert diameter
Exit insert length
Tailpipe length
Resonator diameter
Resonator length
Exhaust gas temperature
The program will predict the dB noise attenuation and frequency range output.

With any kind of luck (and patience) you could make almost anything sound like a Harley. :lol:

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Re: Making a muffler

Post by lefty o » Tue May 21, 2019 10:26 pm

David Redszus wrote:
Tue May 21, 2019 8:04 pm
emsvitil wrote:
Fri Apr 21, 2017 7:13 pm
The termination boxes aren't mufflers (although they may quiet things a bit)

They're to fake out the exhaust system into thinking the headers open to atmosphere, rather than into a exhaust system...
Bingo!

The exhaust pipes should end at a certain tuned length from the head. This tuned length is far too short for most vehicles.

The trick is to insert a large diameter resonator at the proper distance, and then run free flowing pipes to the rear of the car.

I built such a system for a road racing BMW for a race at Road Atlanta. It easily passed the track noise limit but was very noisy inside the car. Sheet metal floors resonant quite a bit. Fastest car in class. But then it rained and the driver crapped his pants.

Prof Gordon Blais devotes an entire chapter to the design of noise cancellation exhaust plumbing in his Four Stroke book.
The required measurement inputs are:
Inlet insert diameter
Inlet insert length
Exit insert diameter
Exit insert length
Tailpipe length
Resonator diameter
Resonator length
Exhaust gas temperature
The program will predict the dB noise attenuation and frequency range output.

With any kind of luck (and patience) you could make almost anything sound like a Harley. :lol:
its hard to make anything else sound like a v twin with a miss. LOL

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Re: Making a muffler

Post by ptuomov » Wed May 22, 2019 7:47 am

A cross plane V8 without any crossover between banks isn’t too far from a pack of Harley’s, no?

During this project, I think I figured out that any methods for muffler design that don’t take into account the mean gas flow velocity aren’t in practice very predictive.

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Re: Making a muffler

Post by David Redszus » Wed May 22, 2019 10:51 am

ptuomov wrote:
Wed May 22, 2019 7:47 am
A cross plane V8 without any crossover between banks isn’t too far from a pack of Harley’s, no?

During this project, I think I figured out that any methods for muffler design that don’t take into account the mean gas flow velocity aren’t in practice very predictive.
I think you mean mass flow. Sound attenuation does not require a reduction in mass flow properties, although some designs (i.e. SuperTrap) certainly do.

Flow reduction is normally encountered when pipe diameters, pipe bends and pipe lengths are not considered. What is the total flow reduction (head loss) from the head to the back end of the vehicle?

What is the diameter of your exhaust pipe(s)?

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Re: Making a muffler

Post by ptuomov » Wed May 22, 2019 11:04 am

David Redszus wrote:
Wed May 22, 2019 10:51 am
ptuomov wrote:
Wed May 22, 2019 7:47 am
A cross plane V8 without any crossover between banks isn’t too far from a pack of Harley’s, no?

During this project, I think I figured out that any methods for muffler design that don’t take into account the mean gas flow velocity aren’t in practice very predictive.
I think you mean mass flow. Sound attenuation does not require a reduction in mass flow properties, although some designs (i.e. SuperTrap) certainly do.

Flow reduction is normally encountered when pipe diameters, pipe bends and pipe lengths are not considered. What is the total flow reduction (head loss) from the head to the back end of the vehicle?

What is the diameter of your exhaust pipe(s)?
I meant that if there's no gas flowing thru the muffler, the insertion loss is very different compared to the case in which gas is flowing fast thru the muffler.

From some old mesurements:

Static pressures measured normal to flow, in psi:
Barometer 14.80
Turbocharger Suction Pressure (ABS) 13.85
Intercooler Pressure Delta (DIFF)1.30
Intake Manifold Pressure (ABS) 30.69
Downpipe Pressure (ABS) 15.97

So say 1.2 psi back pressure.

It's dual 3.5" system with that merges the flow twice for sound suppression. Two 3.5" resonators, merged cross-over, two 3.5" mufflers, and a big muffler at the merged tail pipe.

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Re: Making a muffler

Post by David Redszus » Wed May 22, 2019 7:40 pm

ptuomov wrote:
Wed May 22, 2019 11:04 am
David Redszus wrote:
Wed May 22, 2019 10:51 am
ptuomov wrote:
Wed May 22, 2019 7:47 am
A cross plane V8 without any crossover between banks isn’t too far from a pack of Harley’s, no?

During this project, I think I figured out that any methods for muffler design that don’t take into account the mean gas flow velocity aren’t in practice very predictive.
I think you mean mass flow. Sound attenuation does not require a reduction in mass flow properties, although some designs (i.e. SuperTrap) certainly do.

Flow reduction is normally encountered when pipe diameters, pipe bends and pipe lengths are not considered. What is the total flow reduction (head loss) from the head to the back end of the vehicle?

What is the diameter of your exhaust pipe(s)?
I meant that if there's no gas flowing thru the muffler, the insertion loss is very different compared to the case in which gas is flowing fast thru the muffler.

From some old mesurements:

Static pressures measured normal to flow, in psi:
Barometer 14.80
Turbocharger Suction Pressure (ABS) 13.85
Intercooler Pressure Delta (DIFF)1.30
Intake Manifold Pressure (ABS) 30.69
Downpipe Pressure (ABS) 15.97

So say 1.2 psi back pressure.

It's dual 3.5" system with that merges the flow twice for sound suppression. Two 3.5" resonators, merged cross-over, two 3.5" mufflers, and a big muffler at the merged tail pipe.
What diameter exhaust pipes are you running into the resonators?

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Re: Making a muffler

Post by ptuomov » Wed May 22, 2019 8:09 pm

The resonators take in 3.5” pipes. The pipe size goes up to 3.5” at the point where the wastegate sump pipe merges to the flow. There are photos earlier in this thread.

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Re: Making a muffler

Post by David Redszus » Thu May 23, 2019 12:16 pm

ptuomov wrote:
Wed May 22, 2019 8:09 pm
The resonators take in 3.5” pipes. The pipe size goes up to 3.5” at the point where the wastegate sump pipe merges to the flow. There are photos earlier in this thread.
Reviewing a silencer design program, I find that a straight thru, perforated tube, design will attenuate noise at specific frequencies, without flow loss. The issues to address are: packaging, attenuation targets by dB and frequency. Other design factors are gas temperature and wall thickness.

How much noise reduction do you need?

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