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Quiet -- stock like sound level -- turbo back exhaust

Exhaust 
78K views 149 replies 47 participants last post by  dlheman 
#1 ·
Hey guys. I have a 2016 sti, and am planning on installing a turbo back exhaust. Ideally I would install a catted DP and keep the cat back stock, as I'm happy with the sound.. But I don't want the restriction of the stock exhaust. I know it will be louder, but I want to keep the noise increase to a minimum, and definitely no drone on the hwy. Recommendations? TY.
 
#52 ·
If anyone can find the unicorn exhaust that doesn't drone on the highway with a catless downpipe, let me know. I've researched and searched video clips until red in the face. Corsa seems like its the most promising, but with a catless downpipe, even it seems like it would be too loud.
 
#53 ·
I'm Tairy Greene. There's a lot of chatter. CHATTER, not cheddar! Is there cheddar?

A lot of ppl will say the Corsa is not too loud or they even want louder, however many do also complain about drone w that one. It's definitely hard to narrow down given all the combinations of variables plus the relativity of personal perceptions in the first place.
 
#56 ·
So I had the SPT and the drone became outright ridiculous when I added my Spoolinator kit which was catless at the time. I can’t imagine any amount of resonators solving that. The Corsa was way better than that.

No, the issue never was resolved. The vendor who I bought it from was helpful in managing the attempt and got a middle man to provide a replacement piece at cost. I do like the exhaust otherwise. Was a bad weld on one of the tips.


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#82 ·
So I had the SPT and the drone became outright ridiculous when I added my Spoolinator kit which was catless at the time. I can’t imagine any amount of resonators solving that. The Corsa was way better than that.

No, the issue never was resolved. The vendor who I bought it from was helpful in managing the attempt and got a middle man to provide a replacement piece at cost. I do like the exhaust otherwise. Was a bad weld on one of the tips.


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I have the SPT on a 15+ STI with Killer bee header, stock intake with HKS Funnel, Cobb catted DP and I do not have drone, the sound is deeper.

I amconsidering the SINGLE Q300, weight savings and some hp, but I could not find anyone with one installed. According to Invidia the noise level is 93 db. Any feedbacl would be nice.

BTW everytime I start the STI the alarm of my neighbour's M4 triggers :)
 
#59 ·
I'm sure it's true to a certain degree that you're going to add noise when you de-restrict the exhaust to make more power. But honestly 10 hp in the grand scheme of things is not worth it to me. If it's so restrictive that throttle response is terrible etc okay that's one thing, but if we're just talking about gaining a small amount of power I'd rather cut down on the noise a bit. I guess there's always the Maddad Whisper but some even say "whisper" is a misnomer for that exhaust :-/
 
#60 ·
My car is stock w/ CBE and no tune right now, but I had 2 stage 2 WRXs before and the Tomei has maybe half the effect on responsiveness and high rpm power vs replacing the stock DP with an aftermarket catted DP and stage 2 tune for 91 octane (I'm in CO). I was actually very surprised after install, I was expecting nothing.
 
#62 ·
Anyone welded in an additional resonator (or 2) to an aftermarket exhaust? I had R400 on my car for 1 day before I sold it, but I was tempted to weld in a Vibrant resonator to try to calm the boomy drone. If I didn’t have a local buyer with cash in hand, I might have tried it.
 
#63 · (Edited)
Corsa is the quietest cruising exhaust I have heard, and I have had 3 exhaust on my car, and probably have heard 8 in person.

I am mainly referring to cruising and normal driving (not full throttle)

It's much quieter than the Cobb I had which was pretty bassy and really got into the cabin, especially around 2400 rpm.

It's the tone and frequencies that are tuned not to be annoying and cause drone or bassy exhaust notes.

The best part is even though it is not obtrusive, the sound is super aggressive and airy, and IMO sounds better than any exhaust you can buy for our cars.

Lastly, if you want even quieter and less "drone" for aftermarket exhaust, don't buy a dual exhaust. Something happens in the Y, and creates extra sound that gets into the cabin. It slightly changes the tone and seems to be louder at around 2-3k with the y in the mix.

I actually had the Y pipe welded as if I am running a single exhaust but left everything else in place, so I technically have a Corsa single, lol.
 
#65 · (Edited)
If "quiet" cruise is what you want, Corsa is pretty much the only option. But don't get a catless downpipe. There really are not many advantages.

With that said, no turboback is quiet on these cars.

If I had to do it all over again, here is what I would do, and I have no scientific evidence to support my theory, but the Y pipe messes the sound up and added noise all in the wrong place.

Buy a single exit tame exhaust like the Q300 (comes out the right side), and be done with it.

The Q300 DUAL and SINGLE do not sound the same, and it's b/c of the Y pipe. If you actually look at any other performance car, none of them do the Y crap. They use a single large muffler section with piping coming out on each end-- much like the GR hatches.

To this day, the absolute best muffler (exhaust) I have heard is the APexi WS2. It in incredible sounding, super aggressive and mean, but really quiet, when you want it to be. It's simply the best of both worlds. Nothing even comes close IMO.

The Corsa is a wannabe Apexi, and the tone is actually pretty similar, but Apexi is definitely quieter and sounds way way better on ELH.

I am strongly considering buying the Invidia 300, chopping the muffler off, and buying the Apexi WS2 muffler. It's that good sounding, all while being drone free at any rpm.

Listen here, but of course, the video does not do justice.
Apexi Noir 2005 Saab 9-2x Aero - YouTube
Subaru wrx apexi exhaust - YouTube

I like the sound catted and with a resonator. It can get way too raspy if you go catless and no resonator, and really noticed once you go ELH.
 
#69 · (Edited)
I put the stock catback on my car with the catless downpipe, and I honestly think it is slightly quieter than stock (in-cabin noise. Pretty sure its louder outside). There is less bass/boom to it. Highway drone is almost non-existent. I'm kinda thinking about adding a Nameless resonated midpipe and keeping the stock mufflers to see how that does.
 
#73 ·
Tomei exits left side... it's a really nice exhaust but it's loud. If I could have something just like it but half as loud I'd be happy. If I was to change anything I'd either put a new muffler on it or sell it for a Q300 single and possibly replace the Q300 muffler with something else.

Anyways, the shape of the Y or T does matter a lot, it's the discontinuity that causes the resonance and is the reason the "dual exhaust" has these issues. Corsa and others use Helmholtz or other resonators designed to eliminate the bassy drone sound so in their case the shape of the split doesn't matter as much.
 
#77 ·
You could defintely chop it off and put a new muffler. Is the Tomei the same exaust they sold for the GR and GD, or is it 15 spefcific, like that Q300 is?

The Corsa still has that drone tone a tad b/c of the dual, but less than other exhaust out on the market, but that is not bc of the resonaotr, it's the muffler design. But do what I do, and block off the other side in the y pipe, but welding it shut. So it's the look of the dual.
 
#90 ·
Today I used an Apple app to measure the noise inside de car. I know is not the most scientific study but is the noise level that I heard inside de car. The phone placed in the central cupholders next to hand brake
. Here are the details:

STI MY17 with KB ELH, HKS Funnel, Cobb downpipe, STP Exhaust.
Radio off, Aircon off
Tires 265 Bridgestone RE-01


Normal driving was btw 3k and 4k @50 mph. I did some pulls to 6k and when reducing gears was using heal and toe. Top speed during the pulls was 70 mph.

I lost the file, but remember that the highest noise level, using Z frecuency, was 93db. At ilde was 85db.

At the end I got a nice offer to buy the Q300 single Exhaust. One I installed will repeat the test

J
 
#103 ·
Today I used an Apple app to measure the noise inside de car. I know is not the most scientific study but is the noise level that I heard inside de car. The phone placed in the central cupholders next to hand brake
. Here are the details:

STI MY17 with KB ELH, HKS Funnel, Cobb downpipe, STP Exhaust.
Radio off, Aircon off
Tires 265 Bridgestone RE-01


Normal driving was btw 3k and 4k @50 mph. I did some pulls to 6k and when reducing gears was using heal and toe. Top speed during the pulls was 70 mph.

I lost the file, but remember that the highest noise level, using Z frecuency, was 93db. At ilde was 85db.

At the end I got a nice offer to buy the Q300 single Exhaust. One I installed will repeat the test

J

Finally I installed the exhaust and swapped the Cobb downpipe for a coated Grimmspeed DP at the same time. It is the last time I decided to do all together on jack stands alone, I am to old for this :(

I have drove the car only 20 miles, I do not want to get into boost zone because I do not have tuned the car.

First impresions: so far, below 4K, the sound is different but not louder, using the same app to measure the STP, I got 88 db. THe Q300 single is much lighter than SPT. The 4in tailpipe fits nicely in the exhaust hole

Once I got the tune an more miles with report results
 
#91 ·
The HKS Legamax Premium and HKS Super Turbo Muffler are the quietest catback exhausts for the 2011+ STI. I've heard everything out there including Corsa, Cobb, ARK, Milltek, Grimmspeed, Maddad and the Q300 to name a few and they are all louder. The HKS systems have a Helmholtz Resonator in the middle for frequency tuning which is the main reason. The Super Turbo Muffler is actually quieter than the Legamax Premium because of the exhaust tips which kinda sucks because they look better. HKS muffler angle and tip arrangement is also perfect! Many other cbe systems have the mufflers & tips sitting in such a way they look as if they are pointing down.
The stock catback is fairly quite when attached to a properly fitted downpipe with HFC like Cobb. The HKS is louder than the stock exhaust when attached to the same downpipe and in all fairness it should be, but barely.
HKS is also releasing an anniversary edition full Titanium Super Turbo Muffler for anyone who wants to spend around $4k. Looks hot though!
 
#92 ·
Very interesting. It doesn't look like they sell the full catback for the 5 door unfortunately (I know this is a 2015+ thread). Of note, it looks like their midpipe is 65mm which is important to those who feel they need a 3" exhaust setup.


I've been waiting 3 months on my Milltek at this point. RallySport Direct (rather unapologetically) doesn't seem to be able to get their distributor to get in contact with them. Along with the price and the crapshoot of build quality, I'm debating cancelling that order. Maybe I could just have a shop fab me a new 3" mid pipe with a good enough resonator and keep the SPT axleback (along with ELH and catted downpipe)...


Keep the info coming, guys. 95% of aftermarket exhausts are out for me because of noise levels, and many of them wouldn't work anyway because of how they interact with ELH.
 
#93 · (Edited)
The midpipe is 75mm for the 15+, it's the 11-14 that is 65mm. Don't want anyone to get the wrong idea. The 15+ HKS Legamax and STM also fits the 11-14 so the one HKS shows for the 11-14 which is 65mmm isn't needed.
Legamax Premium 31021-BF001 used for 11-19 STI Sedan using 75mm primary/midpipe.
Super Turbo Muffler 31029-AF013 used for 11-19 STI sedan using 75mm primary/midpipe.
 
#94 ·
I loved the combo of the catless downpipe and a stock catback. I ran it for almost 3 years. It was the perfect sound increase from stock. Catted would have been the same without the smells or the overboosting in cold temps. Highly recommend it, there's really nothing wrong with the stock catbacks. They perform very well until you get into replacing headers or the turbo.
 
#95 ·
I agree. Even though the catback is worth some power (not much) on stock turbo it's hardly worth it for the money spent so the stock catback is usually worth keeping till it's the last thing remaining. I always prefer a HFC as I've gotten older otherwise the fumes make me nauseous. A good quality HFC will not restrict any power or spool on the turbo so the only thing it hurts is your wallet.
My only complaint was on the 11-14 sedan was how far inboard the tips were which would eventually lead to carbon buildup on the bumper staining the paint. Glad Subaru fixed that on the 15+ cars. Not sure if that was an issue for the hatch? I can't remember how mine was since I removed the oe catback almost a decade ago.
 
#97 ·
I've been doing some reading on Helmholtz resonators vs 1/4 wave. Both are after the same goal, but Helmholtz resonators are based on the velocity of exhaust gases and work on the same principle that causes a sound when the wind or your breath crosses the opening of a beer bottle. 1/4 wave resonators (not sure if there is a more specific name for them - it's basically a closed J pipe) focus more on countering the specific sound waves.

If I had a welder (and the ability to use it proficiently), I would give that a shot. You can try to identify the resonant frequency first, then you basically build the pipe a quarter the length of the wavelength of that frequency if I understand correctly (which in most cases seems to be fairly long, ~ 3 feet). A lot of people actually have one pipe welded on, and then instead of it just being a pipe with a cap on the end, they cap it off with a slightly larger pipe and create a slip fitting so they can effectively modify the length of the J pipe within a specified range. Obviously you'd shoot for the length you calculated, but it sounds like tweaking things even a cm or two can make a difference on effectiveness.

Since DIY welding is out of the question and HKS doesn't have an exhaust with Helmholtz resonator for the GR, I don't think adding resonators will yield great bang-for-the-buck, so I'll likely keep after the Milltek.

With that said, thanks again for the info, this has been an educational moment even if I don't put it into use on my car.
 
#101 ·
Thouuuught I had replied to this but maybe not. (I did)

JW thanks for the tip. I did talk to them, they didn't anticipate being able to ship for several weeks. I'm talking to another American company and a British one to see what kind of prices and lead times I'm looking at. I've waited this long so I don't care if it's here within a week, but I also don't want to wait 3 more months especially now that I've swapped the ELH and downpipe and expect to dislike the resulting interaction with my SPT.

PURE thanks as well. I was looking through their other offerings and I was indeed intrigued by the Super Turbo. It sounded nice in the video and I do like the overall look minus the tips (can't get past the giant dual exit). I don't know if having each runner pass through both silencers actually does anything, but it's cool if it does and I do like the look. Unfortunately, I can't wait for them to decide about building one with quad exit. For the price of the Milltek I guess I could potentially get the HKS and have a shop weld on different tips, I just hate the idea of hacking up a brand new $1000 modification. I toyed with the idea of buying a welder and learning as I go while adding a resonator to my SPT but the last thing I need is more "occasional use" equipment. And if I'm putting forth any effort on this whole shebang I do want to go ahead and have a 3" exhaust for the future.

I did cancel my order with RSD and won't buy from them again due to the combination of this situation along with other issues I've had. I realize they are huge and won't know the difference and that's fine, but I will feel better giving my money to a company that deserves it.
 
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