Exhaust Drone is Completely Gone

[tonystang]

Originally Posted by steve_stang2003

Hey!!!
I'm an old fart too!!! (no insult intended, but many of these boards are mostly young whipper snappers!!)

I'm 48YO for the record....

Here is the deal with the 2V engines....Specifically my vert....
First, understand that the vert is going to make things worse due to the open back end where the top lives which acts as a huge bass drum..Also the soundproofing in the vert is less than the coupe, although my car is pretty much Dynomatted (don't waste your time and $$$ BTW)...

The Maggies are a great exhaust for people like us because they are just about +1 over stock during idle and normal cruising but if you stomp on it they will scream really nice.
They do drone however, but it is just an annoying peak at 2000 RPM or so. You can easily talk, listen to the radio etc even though it is there.

To compare, I have been in other cars where the drone is so bad, your ears literally feel like they are going to implode and start bleeding.

The Maggie system is NOTHING, NOT EVEN CLOSE, to that...
The droning amounts to a humming noise that peaks at 2000 RPM or so.
Many people like it. Many hate it... I have gotten used to it but I still would like to eliminate it because I feel it makes the exhaust sound poor in that range....

Baed on your description I would say the Maggies are a good match.
My wife hates loud cars and she always drives mine with no complaints.

Everything is relative and like I said you can find systems that will split your ears...
The Magnaflow 15671 is not one of them. It's very tame.
Avoid the Magnapacks though as they are really loud...

I can send you a sound clip if you have a place that can handle a decent sized file, say 4 meg or so...

Hey fellow old fart! Thanks for the feedback. That helps. Sound clips are tough to really get an accurate feel for how loud things will be. My Magnaflow system on my Cobra was also pretty tame, but would bark when you got on it, just like you said. I think my mind is made up now. Thanks again, "old geezer".
Tony

[VORTECD]

The whole exhaust system makes a difference not just the mufflers. I have a '01 Bullitt and changed to BBK long tubes with a pypes x-pipe to start. I then added the magnaflow cat back and it sounded only a little louder at idle and cruising. It does get pretty loud at full throttle but it has no drone at all. It also has cams and a Vortech. A good friend of mine has a Viper GTS. After changing the exhaust he had a really bad drone to it. He then changed the rockers and the drone went away. The rockers added more lift and must of changed the harmonics somewhat. So I guess that is why if 2 people have the same mufflers one may have a drone and the other doesn't if there are others things different in the exhaust or engine.

[Cougar5.O]

Wow, this thread is still going! I can hardly stand to drive my car due to the drone! I keep searching and searching and there's no silver bullet other than driving my car off a cliff (the drone resonance inside the car is like 96 dB!!).

I keep hearing:

- get cats!
- long tubes
- Bassani exhaust tip inserts
- resonator tubes (this thread)
- Corsa mufflers

There, I just summed up many hours of searching for a solution that lets me enjoy drving my car again. I am looking into the Corsa mufflers now - I wonder if they flow as good as my Magnaflows (I have 18" long Magnaflows, for all the good the extra length did me ). Dronemasters, Super Turbodrones, Magnadrones - it's all the same, the system has to be changed to kill the ####ing drone!

Hmmm, apparently the Corsa uses the same technology discussed in this thread, except the resonant pipes are within the muffler (damned expensive muffler too!)

[steve_stang2003]

Originally Posted by Cougar5.O

Wow, this thread is still going! I can hardly stand to drive my car due to the drone! I keep searching and searching and there's no silver bullet other than driving my car off a cliff (the drone resonance inside the car is like 96 dB!!).

I keep hearing:

- get cats!
- long tubes
- Bassani exhaust tip inserts
- resonator tubes (this thread)
- Corsa mufflers

There, I just summed up many hours of searching for a solution that lets me enjoy drving my car again. I am looking into the Corsa mufflers now - I wonder if they flow as good as my Magnaflows (I have 18" long Magnaflows, for all the good the extra length did me ). Dronemasters, Super Turbodrones, Magnadrones - it's all the same, the system has to be changed to kill the ####ing drone!

Hmmm, apparently the Corsa uses the same technology discussed in this thread, except the resonant pipes are within the muffler (damned expensive muffler too!)

All these cars with aftermarket exhaust systems drone to some degree, the Corsa may be the exception though. The problem is that different people hear different things and what is considered drone to one person is just loud exhaust to another. They are not the same though.
The laws of physics pretty much guarantee that these systems will drone.
The only thing that can be done is muffle the drone, like the stock system does or reflect the exhaust gas back on itself and cancel the drone out.
If you listen carefully to a stock system, you WILL hear drone.
It's just muffled and of course the downside is the stock system doesn't breathe well due to the muffling.

I've gotten used to my Magnadrones but I'm considering the Corsa mufflers as soon as I can hear a clip of a stock SN95 running them.
The clips on the sites are either Foxbody, heavily modified or the Cobra both of which sound way different from my car.

Edelbrock also makes a muffler that uses baffles to reflect the sound but I'm not sure if this is to cancel drone or change the sound quality.

http://www.edelbrock.com/automotive_..._muffler.shtml

If anyone has a clip of SN95 with Corsa mufflers please post it!
TIA

[Cougar5.O]

I didn't know they had videos on the site - I'm sold! There was no discernable drone on any of the Mustangs in the videos! Not sure why you think the SN95's in their videos would sound so much different than yours.

[steve_stang2003]

Originally Posted by Cougar5.O

I didn't know they had videos on the site - I'm sold! There was no discernable drone on any of the Mustangs in the videos! Not sure why you think the SN95's in their videos would sound so much different than yours.

Because the two cars on the site are way different sounding than the SN95.

They have a Cobra, no cats, and a 5.0L Foxbody.

Both, even in stock form, have a way different sound than a 4.6 2v SN95.

Are there clips I am missing?

[Cougar5.O]

I bought the Corsa mufflers - they did absolutely NOTHING to reduce drone. It was 92 dB peak with the 18" Magnaflows and it is now 92 dB @ peak drone with the Corsa mufflers.

I'm pissed - nearly $400 and I removed perfectly good Magnaflows in the process - what a waste. Time to set the car on fire

[steve_stang2003]

Originally Posted by Cougar5.O

I bought the Corsa mufflers - they did absolutely NOTHING to reduce drone. It was 92 dB peak with the 18" Magnaflows and it is now 92 dB @ peak drone with the Corsa mufflers.

I'm pissed - nearly $400 and I removed perfectly good Magnaflows in the process - what a waste. Time to set the car on fire

That really sucks!!

Did you have the full Magnaflow catback 15671?
That's the one I have.

How did they install?
IOW did you have to cut or bend anything in order to fit them into the Magnaflow pipes?

Aside from the drone, how do you like the sound?
Can you post a clip showing the drone if it's not too much trouble?

[MFE]

One distinct magic bullet is to create a bigger difference in effective length between each side of the system. Or put a resonant chamber in it like the original poster did.

[steve_stang2003]

Originally Posted by MFE

One distinct magic bullet is to create a bigger difference in effective length between each side of the system. Or put a resonant chamber in it like the original poster did.

The Corsa's claim to do the latter.
They are supposed to reflect the resonant frequency back upon itself, 180 degres out of phase and thus cancel the drone.

I've heard them in Vettes and also in S197 cars and they do work very well.
Evidently they don't seem to work too well for the 4.6L 2V cars, at least according to this thread.

I'm suspicious as to why there is no SN95 in STOCK form clips to be found anyplace I have looked.
Maybe I just haven't found them.

Th Foxbody, Cobra and highly modified SN95 cars sound WAY diiferent than a stock SN95.
It's like comparing apples and oranges.

[MFE]

Originally Posted by steve_stang2003

The Corsa's claim to do the latter.
They are supposed to reflect the resonant frequency back upon itself, 180 degres out of phase and thus cancel the drone.

I've heard them in Vettes and also in S197 cars and they do work very well.
Evidently they don't seem to work too well for the 4.6L 2V cars, at least according to this thread.

I'm suspicious as to why there is no SN95 in STOCK form clips to be found anyplace I have looked.
Maybe I just haven't found them.

Th Foxbody, Cobra and highly modified SN95 cars sound WAY diiferent than a stock SN95.
It's like comparing apples and oranges.

\

LOTS of mufflers do that, using what's called Helmholtz Tuning Chambers. The thing is, they don't do it differently from side to side, so you still have the whole system acting like a big tuning fork. You have to take it out of tune with itself by creating different resonant frequencies in each side of the system.

[steve_stang2003]

Originally Posted by MFE

\

LOTS of mufflers do that, using what's called Helmholtz Tuning Chambers. The thing is, they don't do it differently from side to side, so you still have the whole system acting like a big tuning fork. You have to take it out of tune with itself by creating different resonant frequencies in each side of the system.

Actually Corsa has a patent on their particular process. They make mention of the mufflers being designed for specific cars/applications so is it possible he has the wrong ones?

It looks like he is driving a Cougar which no doubt has different length pipes than a Mustang which in theory will throw the process out of kilter.

From what I can determine, the vast majority of the resonance comes at the tail pipes which like you say act as tuning forks. Some people claim success using different length mufflers on each side. Ford did NOT do this BTW as sometimes claimed, at least not in 2003 as the parts are exact same part number. At least mine are.

With the Magnaflow system the included mufflers are 14 inch I believe. Some people put an 18 inch on one side and it is supposed to help.
I think what is happening is they are just getting more "muffle" on one side.

I've just gotten used to the drone or I use Bassani baffles which takes the edge off a little.

Also the height of the person makes a big difference as well.
I'm 6'1 and have the seat all the way back in my vert.
If i move my head forward or backward the drone is reduced which indicates my head is smack in the middle of a peak node in the drone frequency.

[MFE]

What they have a patent on is the name of the process. Just like Gabriel patented "VST" for their shocks..."Velocity Sensitive Tuning"...well guess what? ALL shocks are velocity sensitive, they just patented the name. Those are helmholtz chambers same as you'd find on many other mufflers. Now maybe Corsa has indeed tuned the chambers for different vehicles, and maybe he got the wrong ones, but the fact remains that the chambers themselves are not likely to kill the drone no matter what length they are. What it needs is significantly different mufflers on each side of the car. Like the factory ones Ever notice they're not identical? One is noticeably bigger than the other. That's why factory mustang exhausts don't drone. It really is that simple.

[Cougar5.O]

My car is a 5L Cougar. I had to add a 2" extender to the Corsa muffler to get it to fit right, otherwise the system is a Mustang (Mor-flo) H-pipe (no cats), Mufflers & Flowmaster stainless LX style tailpipes - all 2 1/2".

I've asked Corsa twice for guidance on this since my (painful as I have arthritis) installation and have received no response at all. I had an email conversation with Corsa before purchasing these mufflers as I wanted to know it they had a longer version of the dB muffler, but they said this was the only one but that it would work on my car. I asked twice if extending it up to 4" on the inlet would matter (I specifically stated that I was worried about the resonant frequency tuning), but they said that should not effect the drone-reduction performance.

Their literature mentions in one place about a 4 dB reduction which would have been OK with me. Note that just before the "drone zone" the sound level in the cabin is about 80-82 dB. It peaks up about 10 dB to 92 dB which is extremely loud and causes me neurological discomfort such that I hate driving my car - the headache just isn't worth it. I always notice that I am gritting my teeth and irritated after a cruise in my car. If I knew these mufflers would offer no help at all, I would have spent the same money ($372 shipped) and bought a cat H-pipe - though I am leary of cats that rattle which drove me almost as insane as the drone. I am considering using the cylindrical high-cell count cats that Pipes and Magnaflow offer. I'm trying to do all this without hurting my track performance or replacing one problem with another (drone for rattling cats).

I made a little video comparison where I am holding a dB meter while driving. The microphone built into my ultramobile is not sensitive to the drone frequency, but I can tell you that the Corsa mufflers sound almost identical to the Magnaflow in every way. The differences are minor as they are both straight-through designs with perforated tube within. The resonant chambers within the Corsa mufflers didn't seem to effect the sound in any way that I could perceive. Here is the link to the video -> http://www.youtube.com/watch?v=hXQ1Opu-J8o

I noticed MFE posted while I was composing this - I wonder if using the 18" Magnaflow on one side and the 15" Corsa on the other would help? It seems like a stupid thing to do after dumping nearly $400 into new mufflers, but I am pretty unhappy after busting my balls on my vacation only to get NO reward for it. I diagonal cut about 2/3 of the outlet of the Magnaflow, but they are definitely reusable as I have a pipe expander and welder on hand. Any thoughts?

[MFE]

that would make a definite difference. But so does simply changing gears when I'm in the Drone Zone, I just switch down a gear. Ahhhhh. Sweet relief.

[Cougar5.O]

Heh, I wish changing gears was as easy as it sounds. 2k is the ideal region to be cruising at and it's difficult to stay out of it. Running at 2.3k or so can be OK, though people tend to slow me into drone when turning, there is a louder than average exhaust tone at higher RPMs and there's those very noisy roller rockers. Below 2k and there is a lot of loading up as I have to be in 5th to do this and the lugging "knocking" sound, vibration and possibly getting into boost unnecessarily make me want to stay in 4th on my back roads.

Anyway, constantly having to "think" by looking at the tach and shifting before it resonates is NO way to enjoy what should be a fun & relaxing cruise in my sporty car.

[steve_stang2003]

Originally Posted by MFE

What they have a patent on is the name of the process. Just like Gabriel patented "VST" for their shocks..."Velocity Sensitive Tuning"...well guess what? ALL shocks are velocity sensitive, they just patented the name. Those are helmholtz chambers same as you'd find on many other mufflers. Now maybe Corsa has indeed tuned the chambers for different vehicles, and maybe he got the wrong ones, but the fact remains that the chambers themselves are not likely to kill the drone no matter what length they are. What it needs is significantly different mufflers on each side of the car. Like the factory ones Ever notice they're not identical? One is noticeably bigger than the other. That's why factory mustang exhausts don't drone. It really is that simple.

Not true.
The factory mufflers, at least on my 2003 GT Vert are exactly the same.
They even have the same part number on them from Ford.
This has been the case with every SN95 I have seen which are 2003 and 2004 year models.

Maybe at one time the mufflers were different sizes, but at least in 2003/4 they are exactly the same.

The reason the factory system does not drone is because the muffler "muffles" the sound. Of course this also kills the performance

If you listen carefully you can hear the factory mufflers drone as well.It just gets squashed by all the "stuff" present in the them. The performance gets squashed as well.

As for the patent, it is not limited to the term RSC..
I believe this is the main patent:
http://www.patentstorm.us/patents/65...scription.html

[steve_stang2003]

Originally Posted by Cougar5.O

My car is a 5L Cougar. I had to add a 2" extender to the Corsa muffler to get it to fit right, otherwise the system is a Mustang (Mor-flo) H-pipe (no cats), Mufflers & Flowmaster stainless LX style tailpipes - all 2 1/2".

I've asked Corsa twice for guidance on this since my (painful as I have arthritis) installation and have received no response at all. I had an email conversation with Corsa before purchasing these mufflers as I wanted to know it they had a longer version of the dB muffler, but they said this was the only one but that it would work on my car. I asked twice if extending it up to 4" on the inlet would matter (I specifically stated that I was worried about the resonant frequency tuning), but they said that should not effect the drone-reduction performance.

Their literature mentions in one place about a 4 dB reduction which would have been OK with me. Note that just before the "drone zone" the sound level in the cabin is about 80-82 dB. It peaks up about 10 dB to 92 dB which is extremely loud and causes me neurological discomfort such that I hate driving my car - the headache just isn't worth it. I always notice that I am gritting my teeth and irritated after a cruise in my car. If I knew these mufflers would offer no help at all, I would have spent the same money ($372 shipped) and bought a cat H-pipe - though I am leary of cats that rattle which drove me almost as insane as the drone. I am considering using the cylindrical high-cell count cats that Pipes and Magnaflow offer. I'm trying to do all this without hurting my track performance or replacing one problem with another (drone for rattling cats).

I made a little video comparison where I am holding a dB meter while driving. The microphone built into my ultramobile is not sensitive to the drone frequency, but I can tell you that the Corsa mufflers sound almost identical to the Magnaflow in every way. The differences are minor as they are both straight-through designs with perforated tube within. The resonant chambers within the Corsa mufflers didn't seem to effect the sound in any way that I could perceive. Here is the link to the video -> http://www.youtube.com/watch?v=hXQ1Opu-J8o

I noticed MFE posted while I was composing this - I wonder if using the 18" Magnaflow on one side and the 15" Corsa on the other would help? It seems like a stupid thing to do after dumping nearly $400 into new mufflers, but I am pretty unhappy after busting my balls on my vacation only to get NO reward for it. I diagonal cut about 2/3 of the outlet of the Magnaflow, but they are definitely reusable as I have a pipe expander and welder on hand. Any thoughts?

I have arthritis too BTW so I know how you must feel.
I disagree with MFE concerning different length mufflers on both sides.
The reason being, that it's mostly the tailpipe that is doing the resonating, not the mufflers.
It's like and organ pipe which is tuned to resonate at about 140hz, give or take a few.

A larger muffler will simply do a better job of muffling the sound which is why people hear a difference in sound.

The only true method of fixing the drone is either a branch resonator or a noise canceling sound done electrically, ala BOSE headphones.

If you look carefully in the Fox body video, notice the guy lets off the gas at the drone zone. Right when the graphics come across the screen "No Drone".
at approx 0:55 in the video.

http://videos.streetfire.net/video/C...L-w_141292.htm

To my ears this thing is droning like crazy under load right before he shifts?

Your car sounds like a sleeping baby compared to that one

I will dig up my sound clips, screenshots and also do the same experiment as you did (I have a SLM) and see what I come up with.

For now, I would call Corsa and express your dis-satisfaction with their product. Send them your video if needed and see if they will accept a return.
Put the Magnaflows back on and don't waste any money on the 18's IMHO.

[MFE]

right...the tailpipes are resonating because both sides of the system are "tuned" to almost exactly the same resonant frequency, and they excite each other like a tuning fork.

If you tune the system so that the effective length is different from side to side, you also change the relationship between their resonant frequencies, and they no longer excite each other as much, aka "drone".

The alternative is to change the resonant frequency of the entire system as a whole, so that the excitation takes place at a frequency that's either more pleasing to the ear, or out of its range of sensitivity, and that's where additional resonators/resonating chambers come into play.

People have had success putting two different styles of muffler on the car, say a Super Turbo on one side and an Aerochamber on the other. Or a Flowmaster 3-chamber on one side and a 2-chamber on the other, which I've personally experienced. It didn't eliminate the drone but it reduced its volume and shortened its range.

[steve_stang2003]

Originally Posted by MFE

right...the tailpipes are resonating because both sides of the system are "tuned" to almost exactly the same resonant frequency, and they excite each other like a tuning fork.

If you tune the system so that the effective length is different from side to side, you also change the relationship between their resonant frequencies, and they no longer excite each other as much, aka "drone".

The alternative is to change the resonant frequency of the entire system as a whole, so that the excitation takes place at a frequency that's either more pleasing to the ear, or out of its range of sensitivity, and that's where additional resonators/resonating chambers come into play.

People have had success putting two different styles of muffler on the car, say a Super Turbo on one side and an Aerochamber on the other. Or a Flowmaster 3-chamber on one side and a 2-chamber on the other, which I've personally experienced. It didn't eliminate the drone but it reduced its volume and shortened its range.

I agree in part that sympathetic vibration is adding to the problem, but the effective length of the system is still the same. What I think is happening, at least with respect to the 18 vs 14 inch Magnaflows is that the 18 inch *muffles* better so effectively you are cutting the sound volume out of one half of your system, which of course will reduce the drone by some factor. The same could be said of buying only one muffler and leaving one side stock.
I'll bet if 2 18 inch Magnaflows were installed the drone level would go down as well do to the better muffling effect, IOW like stock systems.
Some mufflers do a better job of muffling than others.

On my car, a vert which is the worst possible case for drone due to less insulation in the rear etc, the majority of the vibration seems to be coming from the tail pipes by far, not the mufflers themselves.

My personal feeling is that I have not heard an aftermarket system on a SN95 Mustang that does not drone. I *have* heard the Corsa on the S197 and indeed it does not seem to drone compared to a Borla system on the same car which was really annoying.

What we are dealing with is different people react to drone in different ways and some, nobody in this thread BTW don't seem to realize what it actually is. IOW a system can sound loud and mean and yet not have that annoying peak resonance which IMHO kills the exhaust sound.

What really surprises me is that nobody seems to have come up with a guaranteed solution to this problem.

(Maybe we should all go into business together!)

After reading and experiencing Corsa mufflers in Vettes (drone worse than Stangs BTW) and the S197, I really thought this was the holy grail. And it still might be in an actual Mustang rather than a Cougar with a Mustang exhaust, although I doubt it.

The other alternative is that maybe Scotty from Star Trek is right in that you can't change the laws of physics.

I'm going out today with my Sound level meter to do some testing in my car with Magnaflow 15671 catback.
I'll try and post later tonight.

[MFE]

Here's another thought: Simply install a resonator in one side of the system and not the other.

[steve_stang2003]

Originally Posted by MFE

Here's another thought: Simply install a resonator in one side of the system and not the other.

That's another idea. Some people say one of those "hotdog" type resonators work but i don't really see any open space where one would fit?

Anyway, I took a drive and using the same sound level meter on A weighted, Slow response but 80db scale, I get barely moving at 1600 RPM and about 82-84db (Reads +2 or +4 on meter) in the drone zone so I am substantially lower in sound level than Cougar5.O even in a vert (top was up) windows closed. This is going up a slight hill accelerating and trying to aggravate the drone. IOW worst case. Notice in the Corsa vid the guy lets off the gas. Best case and not a valid test IMHO.

My system is Magnaflow 15671 catback and I have the stock H-Pipe with the cats....

I suppose I should thank my lucky stars hey????

I have previously recorded sounds and analysis that i will try and post later.

[Cougar5.O]

OK, I've made a little low-res video (I had too many dropouts in higher resolution video mode). You must use decent speakers to listen to this as the low frequencies don't show up much on cheesy laptop speakers. If you use a sub, you may want to attenuate it somewhat as there is low-frequency road noise that is quite high in level in a full-range system. Enjoy the overload @ ~40 seconds.

http://www.youtube.com/watch?v=lA3eJVVkMZg

Corsa was supposed to call me in response to my complaint - they have not done so yet, but I will complain every day for a week, then I will start calling them regularly until they respond. I asked up-front if these would work in my application and they said yes!

BTW, I was already using 18" Magnaflows if that wasn't clear - they did help quite a bit over the 14" versions I had previously. I've had Dynomax Super Droners, Magnaflow 14" droners, 18" droners and now 15" Corsa DB = high droners. They all drone like mad - watch the video.

Originally Posted by steve_stang2003

at 1600 RPM and about 82-84db (Reads +2 or +4 on meter) in the drone zone so I am substantially lower in sound level than Cougar5.O

Holy crap - I'd give my left testicle to have my car that quiet. 92dB is perceived as TWICE as loud as 82dB!!!!! That's the difference between driving next to a 18 wheeler with the window open on the highway (my case) versus a passenger car cruising beside you (your case)!

[Cougar5.O]

On my way to the Fun Ford Weekend, I got a perfect example of why "just shifting" isn't really a good option.

Most of the main roads around here are 2-lane with 50 MPH speed limits. A good cruising speed is around 53 MPH on these roads & this is a typical speed you'll be at whether you want to be or not due to other traffic.

In 4th gear I was @ 2600 RPM and average 17 MPG

In 5th gear I was @ 1800 RPM and DRONING LIKE HELL but averaged 24 MPG.

It's not reasonable for me to have to run the motor at those RPM's and poor milage just to avoid the drone. The cruises to FFW or the beach on this type road are 30-40 miles - a long time to have to deal with the equivalent of a roaring 18 wheeler cab next to you (with your window all the way down.)

The Corsa guy was supposedly on vacation last week, so I'm not sure why he didn't call today

[351Freak]

Not to just throw yet another muffler out there...but I have had luck in the past...twice no less...using a home made X-Pipe and just plain old super turbo mufflers with the curved reflectors inside...they seem to absorb a fair amnt of noise and the reflectors keep up the flow as well.

My main opinion is on the x-pipe though...it helps balance the flow and sound energy...I've never had the exhaust TOO loud except for when it was flows with 2 outlets per muffler dumped at the axles...ouch...

[Leadsled Coupe]

Corsa mufflers were designed for the 5.0 engines in stock or very near stock form in the Fox and apply well to the SN95 bodystyle also.

Your application is pretty far away from their original intent for it so I isn't a surprise although unfortunate it didn't work so well.

From what I hear from a buddy who used to work there, it's amazing how well they work for the application they were designed for.

I'd love to use them for my highly modified engine/ car but I'll have to see if they think it will work or not. Maybe they'll design some for higher cube engines with no cats and LTH's? 8-)

[LaserRed]

Cougar5.0 is there a reason you don't want to do the side branch resonators? That will get rid of the drone for ya.

[Cougar5.O]

I thought the mufflers would work as advertised and confirmed though discussion with Corsa.

I can't weld stainless with my welder and I'm not sure where the resonator pipes would fit on my car. I plan on researching this futher and I may design something on my own to deal with this issue. As a mechanical engineer I thought integrating two different length resonators into the muffler was a pretty clever idea - too bad it doesn't do crap.

Since I'm only making about 30 HP at cruise while the system is resonating like crazy, the idea that the supercharger that isn't doing anything during cruise is contributing to the noise if ludicrous. If the mufflers can't deal with a system that has a very mild cam but is otherwise stock displacement and compression, then they ####ing suck and are a worthless solution IMO.

[ONELOWF]

I became a little more curious about the 90* pipes when I saw an oem intake with two of them, one was actually shaped like a question mark.
They are called Helmholtz resonators.

The easiest way to think of it, is to imagine riding in a car with a sunroof open and the windows up. That annoying thumping of the wind is the air stream over the car being interrupted by the perebindicular opening into the car which is what the side outlet pipes do to the exhaust stream.

I found this.

"Helmholtz resonators are widely used for noise reduction in vehicle induction and exhaust systems. These resonators are usually mounted as side branch volumes to the main induction system, occupying larger space....... for elimination of low-frequency noise character in passenger car...... The principle function of the new inline resonator is the reduction of low-frequency character of inlet noise. "

So, after many exhaust mods that have not helped, I'm going to try it.

[Leadsled Coupe]

Keep us posted. I'd consider them as opposed to expensive mufflers!

[psychoII]

the resonators work

[pokageek]

Yep, I am trying them on my sn95...will report back. They are the DB brand corsa's and red (quieter), made for stangs with heavy mods and lt headers, no cats, etc..

Did yours look like this? Also, mine are diagonal not straight thru the center. BTW yu thought the super turbo's drone? I had those and they hardly droned at all..almost too quiet for me.

[Cougar5.O]

Yep, I got the Corsa DB Red's for mine - exact same muffler with diagonal through. They did nothing for me compared to the 18" Magnaflows I had - the meter and my aching head verified. If you didn't think the Super Turbos droned, then you may be happy with these. 92dB in my cabin is VERY loud though. Let us know how they work out for you...

[pokageek]

Originally Posted by Cougar5.O

Yep, I got the Corsa DB Red's for mine - exact same muffler with diagonal through. They did nothing for me compared to the 18" Magnaflows I had - the meter and my aching head verified. If you didn't think the Super Turbos droned, then you may be happy with these. 92dB in my cabin is VERY loud though. Let us know how they work out for you...

Will do. I also have a decibel meter. I will test it out. My car has a 5 speed g-force trans with a .64 5th which helps out on the HWY. If I were you I would do those 90* tubes like the beginning of the thread.

[pokageek]

Reporting back. HUGE cut in drone guys. Its almost non existant compared to the delta flow flowmasters. My car is @2000 rpm and 65mph roughly and I don't notice a hint of drone until 80mph and then it is sooo little. The mufflers made a tremendous difference and yes, they work. Shifting thru the gears at lower speed no longer makes me cringe and no more low rpm buzzing drone and quiet at idle.

One caveat though and a nice suprise...when you NAIL it, they are as LOUD as HELL! It sounds like the car has NO mufflers when you floor it! and it sounds awesome. Ever hear a hot rod off in the distance like 2 miles away getting on it on a cold night? Then you know what I am talking aout.