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Discussion Starter · #1 ·
Hey, so, I originally put a Yonaka exhaust on my EG hatch and was really happy with how it sounded out of the gate with the stock d15 and 4-2-1 crap evay headers that were on the car when I bought it. I added an ASR brace and away bar about 24 hours later and the muffler that came with it was a no go for fitment wise. After beating down the corner down far enough to fit with a sledge hammer and making it fit, I had a muffler shop swap it with a Borla ProXS 14" long oval muffler. It was a bit louder but still tolerable.

Fast forward, flip the engine to a k20z3 + DC2.2 cams + 4-1 headers and you can see where this is going. Just too darn loud.

I see lots and lots of info very clearly supporting 3" exhaust on the k-series platform, and have had enough 3" exhausts on cars to be well aware that they're not quieter than 2.5" exhausts, but generally not louder by a ton. I want my cake and want to eat it too, though, so I'm kinda hoping I can do a kteller 3" pipe setup with a resonator and chambered muffler (turbo style or otherwise) and end up with as good or better flow than I've got now with less sound.

I've searched and searched and not found a ton on the topic, though, nothing semi recent or super possible at least. I know having restrictions like a muffler further down is definitely less of a performance drag than smaller pipe, so it seems like it should work reasonably well. Is anyone actually running such a thing though? I'm obviously not looking for anything near stock sound levels, but if I could get a sound level close to the d15 with headers, a resonator where the cat goes, and a Yonaka or WS2 exhaust fitted which is made of stainless steel and flows as well or better that'd be outstanding.

I know exhausts are highly subjective, and what's quiet to one person may be really loud to another, so hopefully the note on the Yonaka setup (which is well known to be among the quieter EG hatch options) helps.

What I've found so far is:
Dynomax VT - were pretty quiet at first but all fail in a year or so, also they're not made any more.
Magnaflow Chambered mufflers (unknown model and specs) - are pretty tame and sound nice.
ES oval - sound great, good and quiet, but are out of production
Anything with switchable valves... - sorry, not interested. I'd rather just lose a couple/few hp always.

Anyone got any specific models that work well, are in production, are made of stainless steel, and don't have major flaws? I'd love to hear what you've got and how you like it.

--Matt
 

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Discussion Starter · #5 ·
Thanks, but I'm definitely looking to go quieter than the Street Power. Noise levels in vtec are kinda the primary problem, TBQH. Definitely will seriously consider the turn down though, based on your recommendation. I've just got 2.5" polished straight pipe as a tip now, so nothing spicy in the looks department, and I don't care to go any more flashy than that anyways.

Forgot to mention... I did actually try a chambered muffler between the Yonaka and the Borla, but I made a bad choice due to lack of proper research and it blew up in my face. The ProXS, even being straight through vs chambered, ended up quite a lot quieter than the Magnaflow XL multi chamber I initially tried. So, definitely no to that particular one. There are just so darn many to try and throwing away $100+ per bad choice gets expensive quickly. 馃槶

--Matt
 

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Discussion Starter · #7 · (Edited)
Hrm. I just wish I could find known quieter mufflers! While surely cheap junk, the Yonaka muffler had a huge body. The Borla on there is only 4x9.5 oval. There's tons of real estate for a taller muffler under there...but seemingly no aftermarket mufflers to fill it!

The Yonaka muffler was easily 6" tall, and even more could probably fit down there....but I've just got this dinky frame. There's only so much sound reduction that can be accomplished by a perforated core through a glass packed canister of this size.

103140


The biggest I see is only marginally bigger: Vibrant Performance 1103 Vibrant Performance StreetPower Performance Universal Mufflers | Summit Racing

I see taller options from some companies, like the APEXi WS2 universal muffler, but they only seem to come with long tips already on them that make them a no go.

--Matt
 

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Discussion Starter · #8 · (Edited)
Maybe something like this could work...


Hard pressed to find any sort of reviews on this brand/style on a 4-cylinder of any sort, though, which worries me a touch. I'd just grab a Dynomax Super Turbo and call it a day, but the only one they make in stainless is too long to fit a hatchback with a sway bar.


Ideally, Dynomax would make this little guy in more inlet/outlet diameters and a 2" shorter 馃が Super Turbo鈩 - Offset / Offset - P/N: 17629

--Matt
 

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Discussion Starter · #11 · (Edited)
I see a few off-the-shelf options that have the right diameter, but I have some doubts about all of them.

Greddy:
Marketed as 92dB with a turbo, so probably pretty loud. Doesn't look like the muffler would clear a bar based on their pics.

Thermal R&D:
Has no resonator and is marketed for turbo cars, so I'm guessing it's pretty loud. It does seem likely to clear a rear bar, though. A touch pricy, but I'd happily pay it if it ticked all my checkboxes.

Skunk2:
At the end of my list in the looks department. Seems likely to be quite loud.

1230 Performance:
Not sure on the quality, not much word on the sound level, haven't yet been able to get into from them on whether or not it'll clear a bar.

Haven't encountered any other so far, but I'm thinking none of those are it...no matter how much my mind wants to find something I can bolt right up and have work.

--Matt
 

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Discussion Starter · #14 ·
Greddy wouldn't confirm or deny that theirs would fit with a bar or how loud it is.

Thermal confirmed that it'd be very loud.

1320 apparently clears a bar. I asked for pics and haven't gotten em yet. Seems like it may even be on the quieter side.

I guess possibly 1 for 4 on off the shelf options.

--Matt
 

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Discussion Starter · #15 ·
K, I think this confirms fitment with a bar...
103198

103199

103200


So that seems like the most "direct fit" possibly. Nice big muffler on the back, hit not so big that it encroaches on suspension. I don't know much about this company, but they do seem to be domestically made by a company in NJ.
 

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Discussion Starter · #17 · (Edited)
Looking for reasonably quiet in and out. I could easily have a conversation inside with the Yonaka setup, and it was low key enough not to draw too much attention.

I'm not averse to getting something off the shelf and adding a resonator. I'd need to measure, but it seems like I may be able to fit a Vibrant Ultra Quiet resonator, or some smaller diameter round resonator, beneath the shift box.

I did hear back on the sound level. They claim it to be pretty tame until you get on it (unqualified claim with no reference point, FWIW).

--Matt
 

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Discussion Starter · #21 ·
Ah well that makes all the difference. I am going to a 2.5" exhaust from a 3" and will have it back on the dyno next month. Hopefully with negligible power loss between the two.
I'd think you'd lose nothing at all. Every dyno I've seen, even on untuned bone stock cars, shows gains across the power band with no loss of power anywhere when going from a 2.5" straight through exhaust to a 3" straight through exhaust.
 

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Discussion Starter · #24 ·
We'll that's a shining review for the WS2 muffler. I wonder if I could fit it in a hatch. The long tip is what worries me there.
 

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Discussion Starter · #26 ·
Whelp, my shop prefers to work with the KTeller kit so I ordered their 3" stainless setup. I guess I'll have to buy stainless flanges and hangers since the ones they provide aren't for some reason.

Anyone know how you generally deal with the 2.5>3 inch step up? I'm hoping I can find an off-the-shelf 3-bolt 2.5" flange that steps up to 3". We shall see. Tentatively settled on that stainless works muffler for now, and either an 18" or 24" resonator. The Vibrant ultra quiet resonator apparently won't fit comfortably between the rear heat shields since they're only about 6" wide. I see evidence that one might possibly fit in front of the hangers though if needed.

--Matt
 

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Discussion Starter · #28 ·
I found pieces of pipe that are 2.5鈥-3鈥 and was going to weld a 2.5鈥 2 bolt onto the header, and the other end to the 3鈥 flex pipe with a v band to the midpipe.
Kinda heading the same way. I see plenty of step down flange to pipe setups for header outlets, but not any going up :)
 

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Discussion Starter · #29 ·

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Discussion Starter · #31 · (Edited)
I managed to find a video of that Stainless Works muffler on a 4-cylinder vehicle. Not a Honda, but at least a 2.0L and 3" without a turbo on the exhaust:

Seems promising.

Here's a better cutaway of the inside. It's the same basic design as the Dynomax setup, or any other traditional turbo muffler, just without the flow directors.

103283


--Matt
 

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Discussion Starter · #32 · (Edited)
Ok, I ended up ordering this stuff...

https://www.summitracing.com/parts/WLK-24248
https://www.summitracing.com/parts/WLK-24241
https://www.summitracing.com/parts/stw-tm5c3c3o

I figured the bullet can go ahead of the hangers in the center of the chassis, and the glasspack can go behind it. Both of those pieces are perforated glass packed tubes, so neither should have much (if any) meaningful impact on flow.

Got these things to mate to the header and step up to 3", and to connect the back section to the front section:
https://www.summitracing.com/parts/VPE-1482S
https://www.summitracing.com/parts/VPE-2630
https://www.summitracing.com/parts/MIO-MMCLAMP-VS-3

馃

--Matt
 

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Discussion Starter · #33 · (Edited)
I found some numbers comparing this SW muffler to the straight through variety and open pipes here: Stainless Works Exhaust

Their number show virtually no power loss going from straight pipes to their straight through muffler, and about 2.5% power loss moving to the turbo chambered muffler. Dumbed down to cammed NA k20 numbers, that seems like 4-6hp...which I can live with. A younger me would care about that, but me today would rather be able to comfortably carry on a conversation. 馃槈

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Discussion Starter · #35 · (Edited)
I am going to try going back to 2.5" for clearance as well as sound. What I'm not seeing is the proof that a very restrictive 3" muffler paired with a resonator(s) will give you better performance or the same sound levels as a more straight through design 2.5" exhaust. Even the ws2, which does sound nice and quiet, is only 70mm. I will definitely update with my results next month. I figured to lose in the 5whp range, however I am no expert and will have a definitive answer next month. The numbers will be a little skewed based on the car was tuned with a 3" exhaust and I am not having it retuned with the 2.5", only ran on the dyno to get numbers for race classing. If I lose in the 10whp range I may have it retuned to see if any of that could be gained back.
I don't think anyone has such proof (at the moment at least).

The general experience I've had is that restrictions closer to the engine have a more profound impact than those further from it, but they're all on turbo engines that benefit from as little back pressure as possible so they may not be relevant at all here. In that space, switching to a bigger downpipe and leaving the smaller rear of the exhaust often gets you almost all of the power benefits you'd get from a full turbo back exhaust. The theory I've seen on the topic suggests that having an optimally large space for expansion of hot exhaust gasses nearest to their origin is much more important that full end to end flow.

How, or if, any of that relates to Honda k20 engines is unknown to me. In general, NA engines typically see better lower rev power figures with smaller exhausts. Dyno evidence seems to suggest that not to be true for these ones, though, and shows that they thrive with as little exhaust resistance as possible.

My car will go on the dyno for a proper tune after the exhaust is changed, so I won't have a before figure. I'll share the after figure once I have it, though. Until then, it's sitting in storage. My hope is that a 3" exhaust with a turbo style muffler performs at least as well as a 2.5" exhaust with a straight through muffler, but does so more quietly since the straight through 2.5" setup is too loud for my taste.

FWIW, I wouldn't call a turbo style muffler "very restrictive". It's technically still "straight through" in that exhaust gasses are never forced through louvers/perforations/packing to reach the output. It's just 3 passes through straight sections internally, with the obvious flow disruptions you have at each turn-around. These mufflers, and even their chambered and laminar flow cohorts in the "chambered" space are still far less restrictive than your average stock muffler.

--Matt
 

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Discussion Starter · #36 · (Edited)
I'm starting to consider swapping the bullet for a GESI UHO cat when I get this done now. Cat plus glasspack plus chambered muffler aught not be too loud I'd think. Those cats evidently cause less than 1% power loss, even on 500-850hp applications, so it shouldn't cost a lil old k20 much right?

I was thinking of maybe even swapping the chambered muffler for a straight through, but then I came across this post where a person with 2.5" pipes and a twinloop with a GESI cat was reported as a bit too loud so I figured maybe not...

That person's sentiments were:
Exhaust is louder than I would like, but it isn't obnoxious. It has a nice tone when I floor it, but its louder at part throttle than I would like.

Bottom line is that if you want quiet, then you need a resonator and a chambered muffler.
 

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Discussion Starter · #42 · (Edited)
I don't have any expectations for stock like sound levels. If I can get 3-6dB less than a straight through 2.5" setup I'll be happy with that. I'd have certainly liked to have tried for a twin loop, but they only seem to go up to 2.5" in any reputable brand, so we'll see how the SW turbo muffler and a big glasspack as a resonator goes. 馃
 
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