Length an diameter 99 Seville STS resonator

[Psycho]

Hi

can someone tell me the lenght and the diameter of the resonator pipe?

I want to remove it for some sound benefits

On my former owned 95 STS, I removed the mufflers an I installed aftermaket raptors.

The sound was great....

But the 99 never sounds, like it performs.

regards and thank you... Psycho

[JohnnyG]

I don't think anybody, including myself, understands your question. There are catalytic convertors, then a "Y", then a long single pipe, another "Y", the two mufflers are in the back, no resonator.

[Cadillac Jim]

You need a resonator at the position of the catalytic converter because it helps define a resonance in the headers and front Y pipe that is important to high RPM, e.g. horsepower. A good low-restriction cat that still meets OBD requirements will do the job as well as can be done and keep you street legal, so you can pass emissions testing. You need the long pipe to the rear because it defines a resonance that helps your bottom end, e.g. throttle response in normal driving and start-up performance. Your main option is to replace the mufflers.

Most people use Borla Super Turbo mufflers or the equivalent from another manufacturer. More important than the length is the pipe size; both are 2 1/4" in and out; your muffler shop can handle differences in length. I use Borla Pro XS series straight-through mufflers which are a little louder than the Super Turbo in normal driving and give a quite authoritative note at WOT, particularly in the power band.

To keep the quality and reliability of your Cadillac exhaust system, stay with stainless steel mufflers, unless you live in an area with no snow/salt on the roads, and no salty shore. And, make sure that the muffler shop you work with uses stainless steel welding rod.

[growe3]

A resonator in its basic form is to help silence the exhaust noise. It is used in addition to mufflers to further silence exhaust noise.

Removal will increase your exhaust sound, it will have minimal effect on power. On some cars the exhaust will be quite a bit louder, as they are usually coupled with low restriction mufflers. On others not so much, but you may now have some drone.

If you do decide to remove it, replace it with stainless steel pipe and be sure it is welded with stainless steel welding rod.

-George

[Psycho]

I don't think anybody, including myself, understands your question. There are catalytic convertors, then a "Y", then a long single pipe, another "Y", the two mufflers are in the back, no resonator.

Hi

on my 99 STS, there is a resonator directly behind the cat.

And I want to remove it, for a deeper sound.

regards Psycho

[Texas Jim]

I reckon I am dumb....

I don't see a problem...if you want to remove it...remove it.

If you are going to be welding the new pipe in...measure it.

If a muffler shop is going to be removing it...they will measure it.

I don't see a problem here...or I am not understanding what you are asking for.

[Cadillac Jim]

If there is a resonator right behind the cat, it's probably there because the cat isn't big enough to enable the resonances in the manifolds that give you some performance peaks at mid to high RPM. You can probably get what you want by changing the rear mufflers to super turbo types. I have straight-through rear mufflers and have a really great exhaust note. I have a sound clip on my blog but it doesn't do justice to the real thing -- and, if you listen to it, put the WAV file on a CD and listen to it on an audio system that has some real bass. If you have a Bose system in your STS that will do just fine; otherwise you can play it on your computer and listen with headphones if those have really good bass.

[growe3]

If there is a resonator right behind the cat, it's probably there because the cat isn't big enough to enable the resonances in the manifolds that give you some performance peaks at mid to high RPM. You can probably get what you want by changing the rear mufflers to super turbo types. I have straight-through rear mufflers and have a really great exhaust note. I have a sound clip on my blog but it doesn't do justice to the real thing -- and, if you listen to it, put the WAV file on a CD and listen to it on an audio system that has some real bass. If you have a Bose system in your STS that will do just fine; otherwise you can play it on your computer and listen with headphones if those have really good bass.

Hi Jim,

To the best of my knowledge, the catalytic converter has nothing to do with any resonance "control". Its duty (in brief) is to remove/reduce NO2, convert CO to CO2, burn off any unburnt fuel. It has no real effect on any exhaust resonance. The cat is pretty much a honeycomb brick, with some precious metals built in to help do the job.

The resonator itself is just an additional exhaust noise taming component. Desireable on vehicles such as Cadillac, known for its quiet power plant; that is until the Northstar and its intake roar came along. The resonator dampens certain resonance tones, as per its design needs. Swapping in a piece of exhaust pipe in place of the resonator, will just allow the exhaust be a little louder, with possibly a very minor HP gain. I doubt if you would see any real time gains, but it might sound pretty mean.

For any interested, please see the link below for more information on catalytic converters. (Yeah, I know its Wikipedia, but the info is good).

http://en.wikipedia.org/wiki/Catalytic_converter

-George

[Cadillac Jim]

I know what a cat is, and what a resonator is, etc; I'm an engineer as well as a long-time car enthusiast. The cat has an enlargement in the cavity as well as the honeycomb. It breaks up the exhaust system so that the parts in front of it have some rsonances independent of the part to the rear of it. The resonances in front of the cat are the high RPM resonances, and those are the ones that support the mid-to-high RPM part. The intake resonances support the horsepower peak near redline. Some newer cats are pretty small because of improvements in their efficiency.

A resonator is used as part of an overall exhaust system in some designs. An earlier post pointed this out. There is more than one function of a resonator, though. There is more than one function for a cat, e.g., a resonator.

The high RPM resonances of an exhaust require that there be a pressure release within about 18" of the manifold outlet. The cat is it in my Northstar system; in yours it is the cat and an accompanying resonator. I submit that the resonator may have a purpose in helping to enhance a performance-related high RPM resonance as well as possible noise reduction.

In my 1997 year model Northstar exhaust, the low-frequency sound suppression was in the rear mufflers, which restricted and damped/muffled the low frequency sound. With my current straight-through mufflers, my Nothstar sound is much like a 1960's big-block. I have an OBD-compliant low restriction cat that almost certainly helps with the exhaust sound, and I recommend that you consider that for your car. With a bigger cat you won't need the resonator and it would likely work better for performance, being closer to your headers. Slightly lower cat restriction won't hurt either; that should help performance and gas mileage.

[growe3]

I know what a cat is, and what a resonator is, etc; I'm an engineer as well as a long-time car enthusiast. The cat has an enlargement in the cavity as well as the honeycomb. It breaks up the exhaust system so that the parts in front of it have some rsonances independent of the part to the rear of it. The resonances in front of the cat are the high RPM resonances, and those are the ones that support the mid-to-high RPM part. The intake resonances support the horsepower peak near redline. Some newer cats are pretty small because of improvements in their efficiency.

A resonator is used as part of an overall exhaust system in some designs. An earlier post pointed this out. There is more than one function of a resonator, though. There is more than one function for a cat, e.g., a resonator.

The high RPM resonances of an exhaust require that there be a pressure release within about 18" of the manifold outlet. The cat is it in my Northstar system; in yours it is the cat and an accompanying resonator. I submit that the resonator may have a purpose in helping to enhance a performance-related high RPM resonance as well as possible noise reduction.

In my 1997 year model Northstar exhaust, the low-frequency sound suppression was in the rear mufflers, which restricted and damped/muffled the low frequency sound. With my current straight-through mufflers, my Nothstar sound is much like a 1960's big-block. I have an OBD-compliant low restriction cat that almost certainly helps with the exhaust sound, and I recommend that you consider that for your car. With a bigger cat you won't need the resonator and it would likely work better for performance, being closer to your headers. Slightly lower cat restriction won't hurt either; that should help performance and gas mileage.

Jim,

My intent is not to have a debate with you, but to more correctly define the purpose of the resonator, as per this discussion. I am not particularly impressed of your engineering claim, or your long time car enthusiast. It belays the question that was asked. I can also trot out my professional credentials, but my professional career, and my many decades long auto work, which includes way to much to list here, again is irrelevant to this users question.

As always I want to keep in line with the intent of this forum. Supply information that is correct, and not needlessly offend other users. So as per the original question asked, I stand by my suggestion, and I respectfully disagree with your interpretation of what the catalytic converter does; in regards to any resonance control.

If you wish to continue this discussion, or provide further information to me, please send a private message to me., as I think we have gotten away from the original question here.

Regards, George

[Cadillac Jim]

growe3 -- I'm sorry. I was a little miffed when you sought to explain to me what a catalytic converter is. And, no, I don't want to continue the discussion; I tried to point out something to Pshcho that I thought might be important and I'm done.

[joeb]

i was behind a new challenger. it had aftermarket exhaust tips which caught my eye and when he accelerated it sounded like crap. i was not entirely sure what motor he had but it sounded very tinny. no deep rumble or thump to the exhaust tone at all. i could not believe that sound was coming from a V8. maybe it was a clone? with a funky V6? i hear new mustangs with their 4.6 V8 motors and they sound great. nothing at all like a northstar. i wonder if i could find a clip online of a newer STS with the RWD setup and see if any have a good sound. i saw a pic of the AWD STS drivetrain and there is a cat (pre-cat?) connected to each exhaust manifold. not sure if custom long tube headers could be fabbed up to fit in there. maybe a custom dual exhaust could be bent up?

[Cadillac Jim]

You can get great sound from the 1993-1999 Northstar. Some swear by the Borla super turbo mufflers, and I have the Borla Pro XS (excess?) mufflers which are straight-through (the turbos have an S-pipe inside) and I believe that my exhaust note is really great. See my blog for a sound clip.

I would leave the cat and any resonators up front alone. These will kill the deep tones only if there is some restriction behind it, as there is with the production mufflers, and changing anything within 18 inches of the headers may affect high RPM performance.

Rather than take advice and experimenting with your car, you might want to take your car to a muffler shop and have them cut the exhaust pipe in front of the rear mufflers and listen to it that way yourself. Someone posted a video here that clearly showed no mufflers at all be hind the rear Y-pipe and their exhaust note was good, but a little harsh, and not so noisy as to get you a ticket. You might find and listen to that video before sawing pipes on your car; I suggest using headphones to make sure that you don't miss the deeper tones.

Adding super turbo or straight-through mufflers will change the no-muffler sound only by reducing the harshness. Dealers install the super turbo Borlas on new cars at customer request and advertise this with banners in the Service area, so you can't go wrong there. The Pro XS series is definitely louder, particularly at WOT, so your taste may differ there -- but my wife likes it, and the car turns heads and wilts egos when I start it. The engine braking exhaust sound in 2nd gear has been observed to cause young males driving alone to lose all interest in proving anything.

[joeb]

i have always chimed in with my thoughts on exhaust over the years on this board. have not taken the plunge on my sts yet but have put 3 complete new systems on 3 different grand prix's. varying combos of new cats, no cat, resonators, no resonators, mufflers, borla, magnaflow, and so on. i just am not sure a single pipe system can really sound good compared to a true dual with a x-over.

[Ed Hall]

How would the Northstar sound with a set of Thrush tube mufflers like the following: