Borla Exhaust Photos & Video (soon)...
#32
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Hey CoasterG
Thank you for the pics and info on the noise while driving. I was waiting anxiously for your evaluation. How is the noise level compared to stock around town? Just curious, but have you ever had after-market exhaust on a previous car? I was just thinking that maybe you are not used to louder performance exhaust and that possibly the Borla system is within the "normal range" of loudness with performance exhaust systems...just wondering. Thanks again.
- GM
Thank you for the pics and info on the noise while driving. I was waiting anxiously for your evaluation. How is the noise level compared to stock around town? Just curious, but have you ever had after-market exhaust on a previous car? I was just thinking that maybe you are not used to louder performance exhaust and that possibly the Borla system is within the "normal range" of loudness with performance exhaust systems...just wondering. Thanks again.
- GM
Around town the noise isn't an issue, the exhaust settles down well and its only louder on acceleration which its supposed to be and there is no drone.
On the highway, when your driving constantly, is when I have an issue - it tends to have a reasonably loud drone at 2000-2500rpm that drives me nuts. And it gets more intense as the car heats up - for example, its about 55 degrees down here in central FL this morning, driving to work which entails about 20 miles of highway driving the noise was fine. 2 days ago it was about 85-90 degrees and I drove to Orlando, about 60 miles, as the car heated up the noise became more pronounced.
Someone mentioned inserting resonators, I'll have to look into that but there's not that much room down there.
#33
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Just my opinion..
Nice Pics!!!!
I would have thought Borla would have left the resonators ON for the Street Version and eliminated the cats and resonators on the Competition System...
...I guess thats what I would have done.
Basically, your exhaust drones between 2-2.5K rpms & on the freeway (cruising speed), because of NO resonators.
- Joe Z
I would have thought Borla would have left the resonators ON for the Street Version and eliminated the cats and resonators on the Competition System...
...I guess thats what I would have done.
Basically, your exhaust drones between 2-2.5K rpms & on the freeway (cruising speed), because of NO resonators.
- Joe Z
Last edited by Joe Z; 04-18-07 at 10:19 AM. Reason: added: Nice Pics!!! & bolded my statement..
#34
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Its a cheap redesign, the Street version is the Competition System without the 2 additional pipes that replace the 2nd set of cats.
I'm going to email Borla and see what their response is to the droning.
I'm going to email Borla and see what their response is to the droning.
#35
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I don't think any amount of sound deadening via resonators will eliminate the droning. The drone is a harmonic characteristic / resonance of the exhaust system. Basically, there is a natural frequency that is highly amplified due to the pipe width and length (like a trombone). The best way to eliminate it would be with a helmolts filter. Of course, that would take quite a bit of research and testing to figure out the diameter and length of pipe that would cancel out the drone.
Here is a picture of what I'm talking about.
Here is a picture of what I'm talking about.
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Sorry to go off topic, but I have to laugh everytime I see that picture of the s2000 exhaust. It looks excited! haha
Back on topic, does anyone know what kind of calculations it would take to determine the proper size diameter and length of pipe to eliminate the drone?
Back on topic, does anyone know what kind of calculations it would take to determine the proper size diameter and length of pipe to eliminate the drone?
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I have a dyno set for our local motorsports club dyno day, Sat, 4/28.
And I should hopefully have track results by next Wednesday, 4/25 or Friday, 4/27 - I'm hoping for some cool weather.
And I should hopefully have track results by next Wednesday, 4/25 or Friday, 4/27 - I'm hoping for some cool weather.
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Sorry to go off topic, but I have to laugh everytime I see that picture of the s2000 exhaust. It looks excited! haha
Back on topic, does anyone know what kind of calculations it would take to determine the proper size diameter and length of pipe to eliminate the drone?
Back on topic, does anyone know what kind of calculations it would take to determine the proper size diameter and length of pipe to eliminate the drone?
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I don't think any amount of sound deadening via resonators will eliminate the droning. The drone is a harmonic characteristic / resonance of the exhaust system. Basically, there is a natural frequency that is highly amplified due to the pipe width and length (like a trombone). The best way to eliminate it would be with a helmolts filter. Of course, that would take quite a bit of research and testing to figure out the diameter and length of pipe that would cancel out the drone.
I'm sorry but I do have to slightly disagree with your statement...
I really can't get too technical on this right now, but I found some helpful material that should be easier to explain to all.
I highlighted some important key points in red.
Also, the pic was a moving animation.
The sound waves were actually moving in the demo, but I had to take a screen shot to host the photo.
So now they don't move.
Hope this helps...!!
- Joe Z
From "How it Works":
The Resonator
When a wave hits the hole, part of it continues into the chamber and part of it is reflected. The wave travels through the chamber, hits the back wall of the muffler and bounces back out of the hole. The length of this chamber is calculated so that this wave leaves the resonator chamber just after the next wave reflects off the outside of the chamber. Ideally, the high-pressure part of the wave that came from the chamber will line up with the low-pressure part of the wave that was reflected off the outside of the chamber wall, and the two waves will cancel each other out.
The animation below shows how the resonator works in a simplified muffler.
In reality, the sound coming from the engine is a mixture of many different frequencies of sound, and since many of those frequencies depend on the engine speed, the sound is almost never at exactly the right frequency for this to happen. The resonator is designed to work best in the frequency range where the engine makes the most noise; but even if the frequency is not exactly what the resonator was tuned for, it will still produce some destructive interference.
Some cars, especially luxury cars where quiet operation is a key feature, have another component in the exhaust that looks like a muffler, but is called a resonator. This device works just like the resonator chamber in the muffler -- the dimensions are calculated so that the waves reflected by the resonator help cancel out certain frequencies of sound in the exhaust.
There are other features inside this muffler that help it reduce the sound level in different ways. The body of the muffler is constructed in three layers: Two thin layers of metal with a thicker, slightly insulated layer between them. This allows the body of the muffler to absorb some of the pressure pulses. Also, the inlet and outlet pipes going into the main chamber are perforated with holes. This allows thousands of tiny pressure pulses to bounce around in the main chamber, canceling each other out to some extent in addition to being absorbed by the muffler's housing.
When a wave hits the hole, part of it continues into the chamber and part of it is reflected. The wave travels through the chamber, hits the back wall of the muffler and bounces back out of the hole. The length of this chamber is calculated so that this wave leaves the resonator chamber just after the next wave reflects off the outside of the chamber. Ideally, the high-pressure part of the wave that came from the chamber will line up with the low-pressure part of the wave that was reflected off the outside of the chamber wall, and the two waves will cancel each other out.
The animation below shows how the resonator works in a simplified muffler.
In reality, the sound coming from the engine is a mixture of many different frequencies of sound, and since many of those frequencies depend on the engine speed, the sound is almost never at exactly the right frequency for this to happen. The resonator is designed to work best in the frequency range where the engine makes the most noise; but even if the frequency is not exactly what the resonator was tuned for, it will still produce some destructive interference.
Some cars, especially luxury cars where quiet operation is a key feature, have another component in the exhaust that looks like a muffler, but is called a resonator. This device works just like the resonator chamber in the muffler -- the dimensions are calculated so that the waves reflected by the resonator help cancel out certain frequencies of sound in the exhaust.
There are other features inside this muffler that help it reduce the sound level in different ways. The body of the muffler is constructed in three layers: Two thin layers of metal with a thicker, slightly insulated layer between them. This allows the body of the muffler to absorb some of the pressure pulses. Also, the inlet and outlet pipes going into the main chamber are perforated with holes. This allows thousands of tiny pressure pulses to bounce around in the main chamber, canceling each other out to some extent in addition to being absorbed by the muffler's housing.
#41
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A Look Inside
Flowmaster mufflers use specially designed chambers to control exhaust sound and interior resonance.
1. Power chamber. Sound and pressure waves first enter into the power chamber. The DeltaFlow plates split the waves.
2. Balance Chamber. The sound waves enter the second chamber where they are met with a reverse sound wave from chamber three.
3. Resonant tuning chamber. Known as a Helmholtz resonance chamber, this is a specially tuned chamber for the '05 Mustang muffler. This air-filled chamber generates sound waves back towards chamber 2, cancelling out sound wave frequencies in the offending range.
#42
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Another Example....
Lexus puts there resonators between the cats and mufflers... I am sure they have a good reason for it...
More useful info that can be applied to better understand the dynamics of a resonator.
Exhaust gases leave the engine under extremely high pressure. If these gases escaped directly from the engine the noise would be tremendous. For this reason, the exhaust manifold sends the gases to a muffler where they go through metal plates, or tubes, with a series of holes. The pressure of the gases is reduced when they pass through the muffler, so they go out of the tail pipe quietly. The muffler is made of metal and is located underneath the body of the car. It's connected between the tail pipe and the catalytic converter. There are two types of muffler design. One type uses several baffled chambers to reduce noise. The other type sends the gases straight through perforated pipe wrapped in metal or fiberglass. This type of muffler is designed for the purpose of reducing back pressure and, consequently, makes slightly more noise. Since a muffler cannot reduce the noise of the engine by itself, some exhaust systems also have a resonator. Resonators are like little mufflers, and are usually the "straight through" type. They are added at the end of the exhaust system to take care of any noise that has made it through the muffler. The muffler quiets the noise of the exhaust by "muffling" the sound waves created by the opening and closing of the exhaust valves. When an exhaust valve opens, it discharges the burned gases at high pressures into the exhaust pipe, which is at low pressure. This type of action creates sound waves that travel through the flowing gas, moving much faster than the gas itself (up to 1400 m.p.h.), that the muffler must silence. It generally does this by converting the sound wave energy into heat by passing the exhaust gas and its accompanying wave pattern, through perforated chambers of varied sizes. Passing into the perforations and reflectors within the chamber forces the sound waves to dissipate their energy.
Last edited by Joe Z; 04-18-07 at 11:11 AM. Reason: typo
#43
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Wow tons of great info on how resonators work, Thanks Joe Z!
After I film (if I can ever get my camera back sigh), dyno and track my car, I'm going to see about a solution to the resonator issue. So there may be an X-Pipe available solo in the near future if I can't solve it via alternative means.
After I film (if I can ever get my camera back sigh), dyno and track my car, I'm going to see about a solution to the resonator issue. So there may be an X-Pipe available solo in the near future if I can't solve it via alternative means.
#45
EV ftw!!!
Exhaust looks good!
I am surprised that the droning is such a major issue on it though. I guess Borla did not do enough research and testing with it before they released it, otherwise they would have caught this problem.
I did something very similar to my car (99 GS400), but had it custom made. I got rid of everything from the cats up front all the way to the back of the car. New Y-pipe, Magnaflow X-pipe, deleted the resonators etc.
I have very little to negligible drone when driving slowly away from a stop and the engine is cold. Once the car warms up, the drone dissappears completely.
Absolutely no drone at all at highway speeds and the exhaust is very quiet at crusing speeds and city street speeds. It is the perfect setup for a performance focussed-modded car like mine. It is ONLY loud at WOT.
I would love to hear the sound clips once you post them up.
You can hear mine (link in my sig) - with the old muffler setup - I have since swapped out the L-tuned mufflers with a set of Magnaflows and the car is even more quiet now.
I am surprised that the droning is such a major issue on it though. I guess Borla did not do enough research and testing with it before they released it, otherwise they would have caught this problem.
I did something very similar to my car (99 GS400), but had it custom made. I got rid of everything from the cats up front all the way to the back of the car. New Y-pipe, Magnaflow X-pipe, deleted the resonators etc.
I have very little to negligible drone when driving slowly away from a stop and the engine is cold. Once the car warms up, the drone dissappears completely.
Absolutely no drone at all at highway speeds and the exhaust is very quiet at crusing speeds and city street speeds. It is the perfect setup for a performance focussed-modded car like mine. It is ONLY loud at WOT.
I would love to hear the sound clips once you post them up.
You can hear mine (link in my sig) - with the old muffler setup - I have since swapped out the L-tuned mufflers with a set of Magnaflows and the car is even more quiet now.
Last edited by Hameed; 04-28-07 at 08:24 AM.