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Quiet -- stock like sound level -- turbo back exhaust
Quiet -- stock like sound level -- turbo back exhaust
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Old 10-27-18, 11:52 AM   #91
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Default Re: Quiet -- stock like sound level -- turbo back exhaust

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!
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Old 10-27-18, 12:08 PM   #92
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Default Re: Quiet -- stock like sound level -- turbo back exhaust

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.
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Old 10-29-18, 05:02 AM   #93
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Default Re: Quiet -- stock like sound level -- turbo back exhaust

Quote:
Originally Posted by murfnamedsmurf View Post
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.
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.

Last edited by PURE STI; 10-29-18 at 08:09 AM.
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Old 10-29-18, 01:33 PM   #94
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Default Re: Quiet -- stock like sound level -- turbo back exhaust

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.
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Old 10-30-18, 05:11 AM   #95
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Default Re: Quiet -- stock like sound level -- turbo back exhaust

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Originally Posted by Noximus View Post
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.
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.
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Old 10-30-18, 05:31 AM   #96
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Quote:
Originally Posted by PURE STI View Post

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.
Oops. Sorry about that. Thanks for clarifying that. I would just stay in the GR section where I belong except everything except the 15+ forums is pretty much dead.
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Old 11-01-18, 05:28 AM   #97
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Default Re: Quiet -- stock like sound level -- turbo back exhaust

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.
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Old 11-01-18, 08:04 AM   #98
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Default Re: Quiet -- stock like sound level -- turbo back exhaust

Have you tried ECS Tuning Murf? That's where I got mine from and they may have better luck than RSD in getting the exhaust from Milltech.
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Old 11-01-18, 09:03 AM   #99
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Default Re: Quiet -- stock like sound level -- turbo back exhaust

Interesting fact: STI performance cat back exhaust is still available and is being sold by Subaru in Canada for 2019 STI models. It's available as a dealer option.
Quote:
Originally Posted by hallfleming View Post
The Subaru Performance Exhaust isn't an option for the 2019 with the mid-pipe change. Can't speak to the Q330, just the Cobb which I'm old and like cause there's no drone and it's the quietest.
Sent from my PH-1 using Tapatalk

Last edited by openuser; 11-01-18 at 09:11 AM.
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Old 11-02-18, 06:05 AM   #100
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Default Re: Quiet -- stock like sound level -- turbo back exhaust

Quote:
Originally Posted by murfnamedsmurf View Post
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.
HKS makes a Super Turbo Muffler for the hatch but its expensive and has one large tip per side. It looks good from the back but kinda weird from the rear 3/4 angle. I can say it does sound good and it doesn't have a Helmholtz resonator in it. HKS said they were considering making a quad tip version with smaller tips...it would look better IMO.
Super Turbo Muffler:IMPREZA

Last edited by PURE STI; 11-02-18 at 06:08 AM.
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