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Old 03-26-2016, 11:29 AM   #51
Senior Tortuga
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I did this mod yesterday afternoon. It was surprisingly easy to get the mufflers off - just two bolts each and a some rubber hangers to wrestle with. Backed the car up on ramps. Took 10 min to get both off. I undid the bottom rubber hanger first. Install was easy too - took longer to remove the masking tape from the chrome tips than to install them back.

The step drill worked great. It helped a lot to 1) make a tiny dent in the center of the circle dimple to keep the drill from walking and 2) drill a tiny starting hole and 3) use a real drill that plugs in and 4) use some light oil to keep the step drill bit cool. I also have a giant vice with a pipe clamp feature that I used to hold the inlet pipe gently (did not want to crush it).

It did not take long at all to drill them out. The step drill did snag a few times - so be careful the torque can rip the drill out of your hand or hurt your hand. I held the drill with both hands and was careful. It did leave a ridge on the outside of the hole. I used a 4" grinder to remove this ridge - I wore both safety glasses AND a face shield as I had to use the grinder without a guard to get in there. Maybe a dremel like tool would be better safety wise.

I did not do as good a job with my plates. They are almost round. I used red RTV and #6 self tapping sheet metal screws to put them on. Then I taped up the exhaust tips and painted just the backs of the stock mufflers with grill paint. I did one heavy coat - LOL - the opposite of normal spray paint. It looks a little grey when dry, but installed it looks really good to me.

I'm going to get my phone and post the pics below (just realized I started typing w/o the pics handy).

Unfortunately, my wife it out at Costco and my sons are rolling in dirt (I mean playing) in the back yard, so I can't take it on a proper test drive yet as I just vacuumed the last batch of kid dirt out of it yesterday. I'll report on any sound differences later.

My wife did point out that the sound of the engine is part of the fun of owning a sporty car. Loud cars seem faster and more fun. So I expect no HP gain but I am hoping for more fun.

Total cost: $10 for the aluminum plate, $1-2 for some screws. Some RTV left over from a project 4 years ago that was going to go bad if I did not use it soon anyway. Some paint leftover from another project 4 years ago. An hour or two in the garage by myself while my wife watched a chick flick on DVD with music and a good hoppy IPA. So even if it makes no difference, I'm happy b/c I like to tinker.
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Old 03-26-2016, 11:56 AM   #52
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Above - before - this is the side I painted when done with some high temp gas grill paint from Lowes



Above - here is how I clamped it into the vice. Yes my work bench is a mess.



Above - here is why I was happy with the black paint. It really makes the whole muffler about invisible under there. It also makes the chrome tips really pop / stand out. Now I need to polish them a little - but I can't find the chrome polish and I am too cheap to buy more when I know I have some around here somewhere I bought in 1997 (and three moves ago)
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Old 03-26-2016, 12:04 PM   #53
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Here is the step drill I used (the big on in this set of two). I guess my hole is 1 3/8 not 1 1/2. Close enough.

http://www.harborfreight.com/2-piece...lls-96275.html
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Old 03-26-2016, 01:20 PM   #54
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Originally Posted by Ferretts View Post
Ok, what's the difference between your "boxer sound" and "boxer rumble"? As in the other thread. You are quick to dismiss my opinion because it does not line up with yous, but you fail to provide any tangible evidence and resort to name calling and anecdotal references.

You realize the cats are the largest restriction in the exhaust by a large margin. Anything you do after that is negligible, meaning until you remove the cats, whatever you do to the exhaust will yield you little or no gain, and in some cases, hurt performance.

But if you want to waste your time modifying a stock muffler for performance gains, you might as well clean the contact patch of your tires because the performance gains are probably very similar.
I think you have missed the whole point of this thread. The main reason for the mod is to alter the change slightly and to get rid of the horrible drone the stock mufflers have with the factory 15 wrx midpipe. Change out the midpipe with an STi version and do the muffler mod if you choose and you have no drone at all and a little deeper exhaust tone than leaving the factory mufflers untouched.

Fort me the STi midpipe alone was a huge improvement and I was aware giving up my full 3" cat back dual N1 would also result in a loss of about 10hp once I add my catted dp paired to sti midpipe and factory wrx mufflers. For me it is all about reduction of noise. My 3" cat back was fine with Stage 1 and other quad tip option cat backs like Q300 and so forth would even be less quiet but once the dp is added along with other mods the noise increases quite a bit, for some it is too much for daily driving for their own personal reasons
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Old 03-26-2016, 01:24 PM   #55
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SUPER job!!

Just as I thought, the black paint finishes the look.

I have a mandrel with a polishing pad on it that I put in a drill. I put some polish on and jab into my tips ever so often. They come out mirror-like. Gotta get my black paint on, I'm ashamed now.
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Old 03-26-2016, 03:00 PM   #56
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those blackies look awesome
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Old 03-26-2016, 04:09 PM   #57
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Default OEM '15+ WRX Exhaust: Thoughts and Revisions

Wow. Just drove my car after this mod. The annoying part of the sound that I had learned to live with after installing the Cobb catted resonated j pipe is mostly gone. I can now hear my ETS intake better and my 3 port EBCS (both sound cool to me).

I can hear conversation better too. So overall my car is quieter in normal driving and a lot better sounding in sprited driving.

It is also noticeably more responsive. You know when your car is breathing better. I can tell. I made a right in the country onto a 45mph road with great visibility and zero traffic. I went WOT and hit the red line faster. I shifted to second, WOT, then third and looked down. Ooopps! 76mph. Hit brakes hard back to 45. (Special governor safety please don't speed aggressive ticket thing in NC right now. Trying not to speed).

I think on my car these mufflers were the bottleneck. Opening them up just a little made my car quicker and quieter (inside with the windows up anyway).

Keep in mind I made 267.4 WHP and 290ft-lbs on a stingy dyno last month. So my car was not slow. To do a sub $15 mod and get even more out thrills and worries me.

I did a quick run up and down a 70mph speed limit section of 485 to confirm it feels quicker at 60-87 mph too. Takes even less to jump from 62 mph to 87 mph.

I can't say if I am making more power at WOT, but for sure the car moves forward more with less right foot in the same gear, same road, same driver, same traffic situation.

Idle from outside sounds deeper and more mellow, but I am less certain of that change. I doubt anyone but an enthusiast would notice or care about the change at idle.

I spent a lot more money and time putting in sound insulation under the carpet (dyna mat). This mod did more to get rid of the part if the sound I did not want:/like.

Here is the paint I used: Rust-oleum Specialty High Heat. UPC 020066777883

Last edited by Senior Tortuga; 03-26-2016 at 04:15 PM.
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Old 03-26-2016, 04:16 PM   #58
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if i still had my spare set of mufflers i'd do this for sure. but i can't afford the downtime on my own cars mufflers.
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Old 03-26-2016, 04:20 PM   #59
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Thanks for the tip on the polish. Note this mod took less time than a hand wash wax (with ice) and vacuum. Maybe 90 min if you have a powerful drill. This grill paint dries fast. If you only do the back you can start putting it together right away.

I did it late in the day and let the RTV set overnight just in case.
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Old 03-26-2016, 04:24 PM   #60
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PS if my car was stock and I was not handy and I had to buy a drill to do this, I would not recommend this mod. Probably not worth it. But if you have stock mufflers with after market j pipe this is a great mod if you have any experience drilling metal.
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Old 03-26-2016, 05:06 PM   #61
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Quote:
Originally Posted by Ferretts View Post
Ok, what's the difference between your "boxer sound" and "boxer rumble"? As in the other thread. You are quick to dismiss my opinion because it does not line up with yous, but you fail to provide any tangible evidence and resort to name calling and anecdotal references.

You realize the cats are the largest restriction in the exhaust by a large margin. Anything you do after that is negligible, meaning until you remove the cats, whatever you do to the exhaust will yield you little or no gain, and in some cases, hurt performance.

But if you want to waste your time modifying a stock muffler for performance gains, you might as well clean the contact patch of your tires because the performance gains are probably very similar.
Any data to support your Theory that the Catalyst is the largest restriction ?
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Old 03-26-2016, 05:22 PM   #62
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Any data to support your Theory that the Catalyst is the largest restriction ?
There are several other threads on here with before / after dyno results. Also the folks who sell modifications and the tuners say the front part, from the turbo to the middle, is the bottleneck on the exhaust on a stock 2015-16 WRX. The dyno evidence says you get the most substantial measurable hp and torque gains just replacing the part closest to the turbo. You get the least gains replacing the exhaust parts from the rear axle back (mufflers) on a car with a stock exhaust. The mufflers typically make so little difference in how the car runs that you 1) generally don't need a tune/ECM changes and 2) don't cause any issues at all with warranty claims or inspections (in non CARB states)
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Old 03-26-2016, 06:45 PM   #63
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Any data to support your Theory that the Catalyst is the largest restriction ?
Yes, I do.
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Old 03-26-2016, 07:09 PM   #64
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Originally Posted by Senior Tortuga View Post
There are several other threads on here with before / after dyno results. Also the folks who sell modifications and the tuners say the front part, from the turbo to the middle, is the bottleneck on the exhaust on a stock 2015-16 WRX. The dyno evidence says you get the most substantial measurable hp and torque gains just replacing the part closest to the turbo. You get the least gains replacing the exhaust parts from the rear axle back (mufflers) on a car with a stock exhaust. The mufflers typically make so little difference in how the car runs that you 1) generally don't need a tune/ECM changes and 2) don't cause any issues at all with warranty claims or inspections (in non CARB states)
LOL, Impressive
Have dyno'd more exhaust configurations than I care to discuss. A lot of variables apply to your above statement. Below 300 whp a 3" exhaust is overkill on an FA. Didn't say it hurts it. Overkill.
I'm pretty sure the reason for his mod was for sound. You get a bonus flow increase and a deeper tone.
I would bet money my car would lose maybe 5 whp running his set up vs my full 3" turbo back.
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Old 03-26-2016, 07:10 PM   #65
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Yes, I do.
Cool, flow data ?
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Old 03-26-2016, 07:38 PM   #66
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Cool, flow data ?

GTFO with this ****
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Old 03-26-2016, 07:39 PM   #67
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Jobber - I can send you my stock mufflers and just send me back your stockers when your done. Shoot me a PM if your interested.
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Old 03-26-2016, 08:04 PM   #68
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GTFO with this ****
What's the matter ? No flow bench, or dyno's.
Only theory's. Yah, I work with some of them. Everything looks good on paper.

Last edited by turbomania16; 03-26-2016 at 09:46 PM.
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Old 03-26-2016, 10:22 PM   #69
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Jobber - I can send you my stock mufflers and just send me back your stockers when your done. Shoot me a PM if your interested.
naw, i would want 2 sets of mufflers on hand forever. one withthis mod and painted black gloss. the others bone stock.
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Old 03-26-2016, 11:06 PM   #70
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if i still had my spare set of mufflers i'd do this for sure. but i can't afford the downtime on my own cars mufflers.
Knowing you, I think you have it in those arms to get it done in a day! Now this has me thinking to give the dude a ring who I scored my sti mid pipe from and buys his useless new stock mufflers and do this mod
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Old 03-26-2016, 11:21 PM   #71
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Knowing you, I think you have it in those arms to get it done in a day! Now this has me thinking to give the dude a ring who I scored my sti mid pipe from and buys his useless new stock mufflers and do this mod
ya my arms.. im going in for an MRI on my shoulder tomorrow. too much car work.
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Old 03-27-2016, 02:52 PM   #72
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What's the matter ? No flow bench, or dyno's.
Only theory's. Yah, I work with some of them. Everything looks good on paper.

You don't need to be a rocket surgeon to realize that a 3" catalytic converter WILL FLOW LESS than OPEN 3" pipe.

You'd have to be a complete idiot not to understand that. flow bench, dyno, FEA all aside.
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Old 03-27-2016, 04:47 PM   #73
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Originally Posted by anjuna View Post
You don't need to be a rocket surgeon to realize that a 3" catalytic converter WILL FLOW LESS than OPEN 3" pipe.

You'd have to be a complete idiot not to understand that. flow bench, dyno, FEA all aside.
LOl, chill BRO
Was talking about a stock exhaust. All the bricks in that system flow pretty decent, alot of the problem is in the architecture. You act like I'm an idiot for asking about flow data. CFM and back pressure are common numbers in the Catalyst business.

Your 3" open theory is right all of the time on your white board. In the real world that would be correct most of the time. Lots of variables to that one too.

Sorry to get off track OP
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Old 03-28-2016, 04:32 PM   #74
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I mainly just like the fact I can hear my 7 year old in the back seat better when driving it normally (like you would if you had your children with you). In that situation, my set up now has less annoying-to-me sound.
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Old 03-28-2016, 06:11 PM   #75
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I am looking for clarity. Once you drill out the dimple what else needs to be removed inside the muffler and how do you remove it? Does this give the car any more sound such as an axle back would? Thank you.
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