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Discussion Starter #1
Hi everyone,
So almost 5 years after major mods/work was done on my car, I FINALLY got a VI (Vehicle Inspection) "ticket"--thankfully with no fine or de-merit points at the very least. I've been meaning for a long time to "quiet down" my car to really stealth it, and because I have a 2-year-old and another baby coming in November but now, I actually have to do it (within 30 days).

I already have an ETS v.2 Quiet in there, along with a good 'ole Depo-Racing HFC (not a test pipe), but in all fairness to the cop that actually approached me (in a McD parking lot while I was getting Chicken Nuggets for my toddler...sigh), I do have a lot of mods. Here are the "relevant noise making" mods I can of.

Bored/Stroked/Sleeved Block-approx 2.2L now
GSC S2 Cams
DrivenFab (wonder where they are now?) EFR 7163 kit
Depo-Racing HFC
ETS v.2 Quiet Catback

Here's what I'm thinking...
1) Put a vibrant mini-muffler in the cat-pipe area like in UR's mini-muffler HFC. I'm guessing I'll need to move the HFC part forward a bit to fit the mini-muffler behind it, ahead of the Rear O2 sensor location.
HFC Mods.jpg

2) Insert another Ultra-Quiet Resonator or mini-muffler--which do you guys think would be better?--in the "stock resonator" location (I think it's between the fuel tanks). And lastly, a 3rd Ultra-Quiet Resonator or mini-muffler, more forward, somewhere on the mid-pipe. Do you guys know if there is even room for a resonator/mini-muffler there?
Mid Pipe Mods.jpg

I am hoping this will knock the sound WAY WAY back until it is under (or well below) the provincial limit here. I am thinking I need at least one resonator in the system as there is some "resonance/drone" around the 3K-3.5K range which is mildly loud/annoying on the highway.

Any thoughts would be much appreciated!

Thanks!
verkion
 

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honestly, no matter what you do, youre always going to get profiled by the police. totally unfair but thats how it is. to answer your question though, put the resonator on the midpipe.
 

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Discussion Starter #3
Yeah, I know in the mid-pipe. The question is what and how many and where in the midpipe. Anyone know how many dB reduction the Ultra Quiet Resonators are good for approximately? Someone mentioned they noticed a 10dB inside the cabin (which is a lot actually) from just the addition of 1 Ultra Quiet Resonator. I can probably take it down say...a good 15-20dB to be on the safe side.

As for getting profiled by police...naw. I mean, people complain everywhere about them, but they are there to enforce the law and our MVA actually has max allowable sound pressure levels (83dB A-weighting for "light duty" vehicles which include Evo X). As I mentioned, they weren't jerks about it and didn't give me a fine nor de-merits. I actually had a good long chat with them since I was waiting in the curbside delivery of McD's and asked them to walk around and do a more detailed check to see if anything else caught their eye that I might want to change. They happily obliged even though they were on break. They noted my front windows were not dark-tinted (which would have caught their attention), the car was not slammed/lowered too much (I'm on Ohlins but our roads here SUCK so it's "minimally" lowered) etc. The ONLY thing he suggested I might reconsider (sooner rather than later) was the rear tails. I have smoked VLAND LED tails which don't have "apparent" red side reflectors/markers. MVA here requires red side reflectors in back, amber up front (which my stock HIDs do have), so people seeing your car perpendicular, know the direction of travel. Yes, the VLAND tails have illuminated LED side strips, but in the event of light failure, the reflectors will work since they are passive devices. They could have put the lighting on a VI too I suppose, but both were like...naw...its so minor. Other than the sound/noise, nothing would have caused them to raise their eyebrows...both (well 3 since another officer stopped by for a break by then) agreed. We have a bajillion other atrociously modified vehicles through to loads of supercars on the roads here so my car is pretty "stealth."

People who know me/have seen my car will agree...it's a sleeper minus the sound so it's time to truly "sleeper" it. Public opinion here has been clear about "noisy cars" and the police have reacted in kind. I know lots of car enthusiasts etc. are pissed and feel like they are being unfairly targetted, but technically, it IS in the MVA. Police have "cracked down" as of late because the public has been making a fuss about it. At the end of the day, the car enthusiast community (and even then, the sub-community that loves LOUD cars) are a very small minority of the overall public. The only thing that irks me is that the MVA does not specify HOW the SPL are to be measured which is quite problematic IMHO. You can't really "modify" a vehicle to within acceptable range without the measurement criteria.

The cop I spoke to had his SPL meter on a gorilla pod with a 0.5m string attached to it. He said, 0.5m, 45 degree was how they measured, microphone pointing inward so that in dual exhaust systems, it would be the furthest it could be from the other tailpipe. Although not specified in MVA, it does seem to be the common (well documented) testing procedure in a bunch of places.

All in all, I have been intending for a good number of years to actually "quiet" down my car. Now I "have to," which isn't a huge deal minus the fact I have to pay the dealer a stupid fee to do the VI for noise.

Thanks!
verkion
 

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Adding those should "help", but its hard to say how much.

Maybe something like this?
 

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This might be what you are looking for. came across this a while ago. this guy put two resonators on the midpipe. hope this helps
 

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Discussion Starter #7
This might be what you are looking for. came across this a while ago. this guy put two resonators on the midpipe. hope this helps
Yeah...I saw that. If I am not mistaken the Tomei Expreme is one of the loudest on the market so I'm hopeful that if @Ttsumibishi managed to make his exhaust a manageable dB level...I can too.

I also emailed Vibrant about the difference between their 1103 "streetpower muffler" and their Ultra Quiet Resonators. Their response? They are essentially the same except for size. Same design, same packing, same perforated tube, straight-through design. They also provided lots of info on where to place, and spacing. In fact, I've inserted part of their (it looks like a canned) response below. Didn't see a FAQ on their page with this info.

There are 3 key points to keep in mind when choosing and installing a resonator and/or muffler.

  1. Size. The general rule of thumb with Vibrant resonators/mufflers is that the larger the body of the device, the more effective it will be at reducing decibel levels, drone, rasp, etc. Larger volume of packing = more harmonic wave absorption. Alongside the volume of packing material making it more effective, is the shape. This is also part of the reason that the Ultra Quiet is a popular choice over bottle style resonators or round body mufflers. Each time your exhaust valve opens, an exhaust pulse wave travels down your exhaust stream. It bounces in all directions as it moves through the exhaust system. The frequency can be affected by the shape, size and length of chambers, tubing, etc. When the pulse wave gets to a suppressive device with packing material, it goes through the perforated core, into the packing material, gets dampened, hits the outside wall of the suppressive device and travels back to the center to rejoin the exhaust stream. In a round suppressive device, the limitation is to one distance for the pulse wave to travel from core to outer body compared to the Ultra Quiet resonator which has a shape with more variable and longer distances for the pulse wave to travel through. This makes it more effective at attacking a larger spectrum of wave frequency of the exhaust note. The same principle applies to a chambered suppressive device but placement becomes very important because the lack of packing material removes the ability to dampen vibration as the pulse wave travels through the chambers. They rely only on pulse wave reflection to cancel out frequencies. Also, keep in mind, larger diameter tubing exhaust systems can be more prone to increased drone or resonance as there is a larger internal surface area that is undampened for the vibration to be amplified or resonate from.
  2. Placement. This also plays a key role in regards to reducing exhaust drone. For most applications we recommend placement of a resonator in the area under the front seats of the vehicle. Targeting this placement will be effective for drone frequencies that are exhibited at low to mid-range steady state throttle/engine load conditions (ie: highway driving). In many applications the room available for a resonator in this area is limited, so smaller body “bottle style” resonators are often employed. Installing a resonator in this area will help prevent that drone frequency from reverberating through the floor and into the passenger cabin. Keeping the resonator further upstream also benefits in cancelling out that drone frequency earlier in the system, preventing it from travelling the full length of your exhaust. Placement will be dependent upon available space as well and is often the most limiting factor for installation. Placement further downstream in the exhaust path will target higher RPM frequencies and overall decibel reduction. This is typical placement for most larger body mufflers. Use your best judgement in identifying where any drone is occurring, in some cases, resonance frequencies can be at their peak further downstream just ahead of the rear axle of the vehicle, this will be a drone emitting from the rear seat area. Target placement in the area where you identify any unwanted frequency is occurring.
  3. Spacing. When you have a long length of exhaust tubing (more than 5’) without a suppression device, there is an opportunity for exhaust valve pulse wave resonance frequencies to be amplified- much the same way if you were to strike 2 tuning forks that are different lengths- the longer fork will have a higher amplitude of wave pitch along the length for vibration to grow. Your exhaust tubing behaves the same way with the pulse wave sent down from the exhaust valve smashing open and closed at incredible speeds- the longer the length without a suppressive device, the more opportunity for a drone frequency to be amplified. For this reason, it is also ideal to try to prevent placement of resonators and or mufflers too close together so they remain most effective across the length of the system.

Thanks!
verkion
 

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I managed to find an evo exhaust with a branch(helmholtz) resonator: Mitsubishi Evolution X (08-16)

I know there's a lot more of info on it in google, but they basically reduce the drone at low rpm without affecting exhaust flow. It also doesn't quiet the car down much at high RPM so basically only in city driving it will be quiet. If you have access to a TIG it shouldn't be too hard to add one to your exhaust. You can add resonators in the mid pipe like the others said to quiet it down even more.
 

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Discussion Starter #9
The fact that it was APPARENTLY measuring 111dB at 3K RPM would seem to indicate either I have a very loud exhaust overall or that was near a resonant peak. I really should go and measure it with my spectrum analyzer to see for myself. If it is a peak, then yeah absolutely, a Helmholtz resonator would undoubtedly be the most effective device to remove the resonant peak.

That said, if it isn't merely resonance and turns out to be broad(er)-band noise, dampening would be the only option.

BTW, Vibrant and I have been going back and forth on a few ideas. (I cannot believe how responsive, helpful, informative, friendly etc. they are as a company...I'd buy their stuff just based on that!) In the process they've let me know that their 1103 (muffler) has 424 cubic inches of acoustic packing and the 1142 (ultra quiet resonator--same construction as muffler but smaller) has 168 cubic inches of packing.

I sent them a picture of the UR HFC with mini-muffler and he was surprised the cat and muffler were "so close" and was concerned the acoustic material would melt from the temps the cat might reach!

Anyways, I'm waiting for a variety of 1103/1142 from online retailers with good return policies, to see what combination of dampening I can shove in my exhaust chain. I'll keep you guys updated as I go.

Thanks!
verkion

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My first exhaust was the Greddy RS single exit and it was just loud. It droned and it was stupid loud outside.

I then had a muffler shop cut off the muffler and put in the same huge Magnaflow 12589 muffler (5x11 oval) that RRE uses for their quiet exhaust. It has single exit on the driver's side. It looked just like this:


In my car with the Greddy resonator, the exhaust droned inside the car but was super quiet outside. I don't recommend.

I then added a short 3" downpipe and the Ultimate Racing HFC + Resonator you are looking at. It was quiet outside but droned inside. I don't recommend. Super nice welds and it fit great but I think the resonator in this location causes drone.

I then found a used Cobb exhaust and outside of the car was louder but the drone was better. It was still there though.

I then went back to the stock cat and the drone was much better. I then bought a Depo Racing test pipe and the drone again was mostly gone but now it was louder outside the car. Not too loud though.

I then got a Depo Racing HFC and it is only slightly quieter outside the car but almost no drone.

I would try the Cobb catback if I were you. It will be the easiest to add and I know it will sound good with your Depo Racing HFC.

In my car with the short downpipe, Depo Racing HFC, and Cobb catback, outside of the car is not too loud and it only slightly drones at 80 mph in 5th. A little slower or a little faster, no drone.

I have a stock 2.0L engine, stock cams, and stock turbo.
 

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you should look into a Full cat back Corsa Exhaust, they have a superb system that comes with a resonator and it doesn't drone at all in the cabin. it stays quiet until you get aggressive with it. I have a AMS wide mouth - ETS HFC - and than the corsa system. Its a pretty stealth setup for what it is.
 

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Discussion Starter #12 (Edited)
you should look into a Full cat back Corsa Exhaust, they have a superb system that comes with a resonator and it doesn't drone at all in the cabin. it stays quiet until you get aggressive with it. I have a AMS wide mouth - ETS HFC - and than the corsa system. Its a pretty stealth setup for what it is.
What other mods do you have on your car? Just checking to see if our cars are fairly comparable.

Just to be clear, when I had the v2 Quiet prior to motor/turbo work, it was dead quiet.
 

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Discussion Starter #13
Real-time update...so I remeasured "before setup" both outside, and inside the shop at 89dB idle and 109dB at 3000 RPM. This was done with the 20" at 45-degree criteria that the police are using here, which although is a valid standard for measuring sound, is NOT the measurement method for the SPL restriction of 83dB. The 83dB threshold is supposed to be done on a moving vehicle with the measurement equipment 15M away and perpendicular to the direction of travel.

In any case, one Vibrant Ultra-Quiet Resonator in...79dB on idle, and 94-95dB at 3000-3500 RPM. Placement is at the back, where the stock resonator sits. That's a HUGE drop, likely because what was happening before was a major resonance peak, amplifying the SPL in a particular frequency.

In the conversations I had with Vibrant, they indicated I could expect a 2-5dB drop, (3dB in terms of human perception is just noticeable by the masses, 10dB is a doubling of perceived "loudness") from each Ultra Quiet Resonator so getting 13-15dB drop is great.

Putting in #2 now to see how much more I can lower the sound...

Thanks!
verkion
 

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Yeah...I saw that. If I am not mistaken the Tomei Expreme is one of the loudest on the market so I'm hopeful that if @Ttsumibishi managed to make his exhaust a manageable dB level...I can too.

I also emailed Vibrant about the difference between their 1103 "streetpower muffler" and their Ultra Quiet Resonators. Their response? They are essentially the same except for size. Same design, same packing, same perforated tube, straight-through design. They also provided lots of info on where to place, and spacing. In fact, I've inserted part of their (it looks like a canned) response below. Didn't see a FAQ on their page with this info.

There are 3 key points to keep in mind when choosing and installing a resonator and/or muffler.

  1. Size. The general rule of thumb with Vibrant resonators/mufflers is that the larger the body of the device, the more effective it will be at reducing decibel levels, drone, rasp, etc. Larger volume of packing = more harmonic wave absorption. Alongside the volume of packing material making it more effective, is the shape. This is also part of the reason that the Ultra Quiet is a popular choice over bottle style resonators or round body mufflers. Each time your exhaust valve opens, an exhaust pulse wave travels down your exhaust stream. It bounces in all directions as it moves through the exhaust system. The frequency can be affected by the shape, size and length of chambers, tubing, etc. When the pulse wave gets to a suppressive device with packing material, it goes through the perforated core, into the packing material, gets dampened, hits the outside wall of the suppressive device and travels back to the center to rejoin the exhaust stream. In a round suppressive device, the limitation is to one distance for the pulse wave to travel from core to outer body compared to the Ultra Quiet resonator which has a shape with more variable and longer distances for the pulse wave to travel through. This makes it more effective at attacking a larger spectrum of wave frequency of the exhaust note. The same principle applies to a chambered suppressive device but placement becomes very important because the lack of packing material removes the ability to dampen vibration as the pulse wave travels through the chambers. They rely only on pulse wave reflection to cancel out frequencies. Also, keep in mind, larger diameter tubing exhaust systems can be more prone to increased drone or resonance as there is a larger internal surface area that is undampened for the vibration to be amplified or resonate from.
  2. Placement. This also plays a key role in regards to reducing exhaust drone. For most applications we recommend placement of a resonator in the area under the front seats of the vehicle. Targeting this placement will be effective for drone frequencies that are exhibited at low to mid-range steady state throttle/engine load conditions (ie: highway driving). In many applications the room available for a resonator in this area is limited, so smaller body “bottle style” resonators are often employed. Installing a resonator in this area will help prevent that drone frequency from reverberating through the floor and into the passenger cabin. Keeping the resonator further upstream also benefits in cancelling out that drone frequency earlier in the system, preventing it from travelling the full length of your exhaust. Placement will be dependent upon available space as well and is often the most limiting factor for installation. Placement further downstream in the exhaust path will target higher RPM frequencies and overall decibel reduction. This is typical placement for most larger body mufflers. Use your best judgement in identifying where any drone is occurring, in some cases, resonance frequencies can be at their peak further downstream just ahead of the rear axle of the vehicle, this will be a drone emitting from the rear seat area. Target placement in the area where you identify any unwanted frequency is occurring.
  3. Spacing. When you have a long length of exhaust tubing (more than 5’) without a suppression device, there is an opportunity for exhaust valve pulse wave resonance frequencies to be amplified- much the same way if you were to strike 2 tuning forks that are different lengths- the longer fork will have a higher amplitude of wave pitch along the length for vibration to grow. Your exhaust tubing behaves the same way with the pulse wave sent down from the exhaust valve smashing open and closed at incredible speeds- the longer the length without a suppressive device, the more opportunity for a drone frequency to be amplified. For this reason, it is also ideal to try to prevent placement of resonators and or mufflers too close together so they remain most effective across the length of the system.

Thanks!
verkion
that's actually my car now :)

i dont have an easy way of measuring decibels, though I'm happy to take a video of it if it helps
 

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Discussion Starter #15
Hey, it's OK. I actually already had to go get my VI done...passed no problem. (Actually, those tiny little sidelights in the front headlight was out but they replaced them and passed me :p)

So, end result?

No Resonator:
Measured nearfield (50cm at 45 degrees - although they say, outside/open, I tested inside/outside the shop and it made minimal difference...again likely because of being nearfield)
89dB @ Idle (1K RPM)
110dB @ 3K RPM

1 Vibrant Ultra-Quiet Resonator:
79dB @ Idle (1K RPM)
95dB @ 3K RPM

2 Vibrant Ultra-Quiet Resonators:
74dB @ Idle (1K RPM)
85dB @ 3K RPM

What I should do actually, is put a 1/4 wave or a Helmholtz resonator near the downpipe to cancel out the remaining 100Hz peak...not that I really need to, but I'm 100% sure, "that's my culprit." If I had done that, 1 resonator would be more than sufficient to do the rest of the "wideband sound" dampening.
 
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