Its the double resonators that make it quiet, not the restrictions. A straight piped 2" exhaust would be loud without those resonators. I had this exhaust on my WRX a while back, and I liked that it was one piece, and just quiet enough, but it did taper down to 2.5". If this was 3" all the way through, Id probaby own one right now.

 

That is completely false !! Your only assuming "double resonators quiet things down substantially" . It's quiet because it's restrictive just like your previous exhaust had the 2.5" restriction . The smaller the diameter the quieter with all other things equal such as number of mufflers and type etc.. I have owned double resonator (non restrictive style) exhaust and they were not quiet . Resonators don't quiet an exhaust down by much , they mostly change the tone like fine tuning the note .

 

17 years automotive experience bud. Take those two resonators out and you end up with a drastic difference, just like you would if you took out your test pipe and replaced it with a resonated test pipe. So, that is completely TRUE. I'm not saying a 3" exhaust isn't louder than a 2.5". I'm saying that the resonators quiet the exhaust down more than reducing the diameter. Go take a look at an Invidia G200 catback and ask me why a straight through 3" exhaust like that is so quiet. It's the damn resonators. You can't argue with facts man. Tell ya what, go ahead and build a 3" exhaust using back to back to back resonators all the way through and then tell me how quiet it is. Then make a 2.5" straight pipe exhaust all the way through and tell me how quiet that is. Betchya the 2.5 is ***** louder.

 

Resonators work. I went from a Perrin HFC to a resonated test pipe and outside of WOT, picked up no extra noise. And you can get full 3" ID resonators.

 

This should help you out. Hey its ok, we all learn something new on here sometimes. This should clarify your incorrect belief about resonators.

http://auto.howstuffworks.com/muffler4.htm

"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"

 

I dont mean to sound like a d**** and we are here to share and learn. However I am correct in regards to this topic.

We are discussing straight flow through perforated resonators. The link you posted is a totally different resonator from what we are discussing. That resonator works by trying to bounce exhaust waves on walls through chambers and other restrictions and creating a lot of back pressure in the process. Since when have you seen an Evo with a resonator that looks like that ? Inlet and outlet next to each other... The working design looks more like the OEM muffler.

This is the resonator we are discussing here.
http://auto.howstuffworks.com/muffler5.htm

Resonators are generally about 1/2 inch thick in the diameter. That means there is about 1/2 inch of sound deadening material in that area. That is not enough to drastically reduce sound, even if you add 2 resonators. I'm not saying it wont lower the decibels, but not as you mention. It will only reduce sound by a small margin and change the tone some, mostly reducing rasp.

 

I went from a HFC to a 6" center muffler and it quieted my car down about 50 % or more during normal driving and a good amount during WOT as well.

 

so how much is this exhaust? How bout a straight shot pic from the rear?

I had an Greddy TIC and it was ***** loud and drony on highway.... ended up trading it for a Tanabe Medallion. Love it. Its nice and deep at WOT and nice and quiet on the highway. Looks good too... NO fartcan look look so less attention from the cops... especially here in VA.

Only gripe with it is you have to get it shorten cause its a bit too long for a JDM rear.

 

You're not being a d***. But if you still think you are correct, I will try to explain it a little better for you to understand. I'll take this to my grave man. I know the resonator in the link I posted is a different style but nonetheless, it is a resonator. That's where we get into the "function" of a resonator no matter what the style is. A resonator is meant to quiet things down. NOT to give your exhaust a specific "note" though it will change it. That is a ricer type comment. There are also different types of mufflers as well. A stock muffler from a Honda Civic is a different style than your basic N1fart can. (Remember the old cherry bomb mufflers?) Obviously an open style resonator will not be able to control sound as much as the one in the link, but they serve the same function. And why would they offer test pipes made from resonators? Because if you removed the cat, you would end up with a louder exhaust. Now, running a resonated test pipe helps absorb SOME of the extra sound that you would have had if it were a straight pipe. Why else would someone add the extra weight of a resonator unless it reduced sound? If the stock outlet of an evo is only 2.5" anyways, then necking down to 2.5" at the catback isn't going to present a noticeable difference in sound or power. I have real world experience proof that resonators do indeed work. Take an Invida N1 exhaust with no resonators, and a G200 with two built in resonators. Both of them straight through. I had both exhausts on my WRX. Straight 3" all the way from the turbo. The G200? Quiet compared to the N1. I know I am correct, but I am just trying to sway your decision to disagree because you are incorrect. There are many noobs on here who look for advice and good information. Please don't sway them the wrong way unless you know 100% for sure you are correct. But this brings us back to the original statement, and I am telling you that the one simple answer is the reason the RM01a is quieter is because of the TWO resonators. You're right, straight through resonators will not control sound as good, that is why the RM01a has TWO of them. Use common sense, why else would they add the extra weight and cost of putting two resonators in a catback? For a specific tone? It's so simple, your overlooking the obvious.

My offer still stands though, build a 3" exhaust out of nothing but resonators and then build a straight piped 2.5" and tell me which is louder. This will answer your question.

I hope I too am not coming off as a d***, but I am trying to prevent the wrong information from being distributed on here.

 

Actually if you want to get into the physics of it, they are very effective. The thin layer of material you refer to is (correctly noted) not effective at a broadband reduction of sound pressure level. What they are effective at is killing the higher frequency harmonics which are the ones mostly responsible for aggravating exhasut notes and percieved loudness. They also knock down droning because droning is caused by a resonance being established in the exhaust system at a particular RPM/Engine load. Resonators alter that resonant frequency (lower it) often below the point where the previous droning occured, thus reducing the drone.

 

This is correct. One big plus I forgot to mention was reduction in drone. Ah, the good ole resonant frequency. Now you got me flashbacking about my DeVry days.

 

Physics according to what formula / calculation? Is there an "Evo specific" resonator? Because every car sounds different and it would need to be tuned for that car and mods. Have you actually done any testing comparing resonator to a muffler? I didnt do any formula's but I sure have switched resonators, cats and mufflers around.

I disagree regarding the higher pitch sound being most aggravating. What annoys the most is the lower pitch deep bass sound. That is what we need to get rid of most to make an exhaust tone less annoying droning sound . There is no special technology out there in which a thin layer of material inside a resonator will do a better job than a larger diameter muffler. At least nothing that I have come across or read. In fact they are the same glass packs.

I'm not speaking of "just theory" . I'm speaking of actual real life switch and compare. I physically put on a resonator(s), listened to it and drove on it daily, HFC and different setups of double mufflers.

A lot of people claiming something to be quiet is just their perspective on what is quiet. Define what your perspective of quiet is? Mine is when I give a friend a ride in my car and they ask me when am I going to replace my "OEM exhaust" and get a turbo back? Has some one ever told you to start your car so that they can hear it and you replied "its already on" ? Has a tuner doing a road test with you after a WOT run and you pop it in neutral suddenly they think the car shut off?

And remember we are talking about straight flow through perforated resonators only.

 

And since this thread is about the fujitsubo, it is not a "quiet" exhaust because of the 2 resonators. It is because of this inside the resonators and or muffler:

 

So you are telling us it is not because of the resonators but whats inside the resonators?

Your not going to win this battle. I'll say this again. Mic check, is this thing on? I've seen the same N1 style exhausts with and without resonators with the same diameter, and the one with the resonators made a HUGE difference. I'm talking about real world results, not opinion here. I did the swap and compare for many years, so since my results are real world and yours are real world, I guess someone has some incorrect info, and it sure as hell aint me.

 

This all makes no sense. A resonator is called a resonator because thats what it is intended to do, no matter what shape, size, or material it is. Just as a muffler can come in many different shapes and sizes. It's the same concept man. You just aren't going to win this argument. These are facts. Look up the definition of a resonator and go away. It is meant to quiet things down, PERIOD.