Megaphone to improve stock exhaust sounds

[edido]

Hello!

I saw a post in Facebook forum (link) about megaphone offered by Fluid MotorUnion. Seems like they eliminate the resonator and replace it with megaphone.

It's the first time I see such a mod. CivicXI and this forum are full of posts about different exhaust options, but nobody mentioned megaphone. It's a cheaper option (sound quality aside as it subjective).

What do you think about it? Any experience? Pros/cons?

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[ender_ong]

There was also another post on Facebook that I saw where they went to an exhaust shop and removed the resonator and replaced with straight pipe, a simpler cheaper approach. Link here:

Facebook Post Integra Type S Resonator Delete

Based on this post, I also did this mod at a local exhaust shop, cost $100. I’m very happy with the results, I use sport mode as default now because the exhaust note is louder and more enjoyable than before. Sport + is also louder as are the pops and bangs. Comfort mode sounds the same as before the resonator delete, so perfect for freeway cruising, no drone at all. Here are pics of my install (no sound clips, unfortunately, but the fb post has some) [ @edido if our NorCal meet happens next month you can hear it in person]

 

[jedi03]

interesting idea...i wonder what power gains are had and what it might sound like on other cars...

 

[Victorofhavoc]

Resonators control drone. Mufflers control volume. This engine sounds terrible without a resonator and you would have excessive drone without it at around 3100rpm. Yes noise is subjective, but I'd wager if you ask 100 people, 70+ of them would blindly judge resonator-less as "worse" sounding.

The concept of a megaphone has been around for decades, and as far back as the gen1 vw bug days from what I recall. Typically they're replacing mufflers to do it and not resonators. It's most common on very small engines, especially motorcycle engines.

Here's the science of the concept... Exhaust is a gas. Gasses move faster when hotter and they lose energy to sound and cooling as they move through a pipe. The megaphone allows the gas to slow down as it opens up because the diameter of the pipe gradually increases, allowing for the gas to slow down and thus produces a lower tone with a gas that has less energy. This is also why a 3" pipe is going to sound deeper than a 2" pipe, all else being equal. The FMU concept (as many other inline concepts have shown over time) is to again shrink the pipe back down and increase velocity. On an NA engine that has two or more runners this makes a lot of sense because of cylinder fire order and different "pulses" of the gas down the pipe (ie, 2cyl, 1cyl, 2cyl,etc in a v6 or alternating fire order in even count banks). The same concept does not exist with a single pipe back from a turbo because the turbo is consuming a lot of that energy and blending the exhaust pulses together in the housing. It will change the sound some, but it will not make the car sound like a car with a flat plane crank and short stroke. Most of the sound change in this case would occur from the loss of resonator and the resulting louder cabin noise.

For easy visualization, compare a tuba to a trumpet. There's only so much air a human lung can push through an instrument, but the tone and volume they each produce is drastically different because of pipe sizing and expansion.

Check out lht performance and the testing they've done with different sizes of piping, resonator, and muffler combos. The best sounding systems on these cars tend to be ones that keep the exhaust velocity up and allow for pass through at the rear muffler section. Ideally you want to just chop that tiny center muffler out to get more noise, but also be able to think when just cruising at hwy speeds. In practice, I tried 5 different exhaust shops and no one around me was willing to touch the rear section on these cars unless it's to just chop it all out or remove the res.

 

[UWU-mancer]

If it’s not a boxer 4 or a v4 best you can hope for is “good”

great on a turbo inline 4 isn’t easy.
I’ve heard i4’s with megaphones and they sound great. But those motors are aided by nice flowing heads, decent headers and liter bike cams at high rpm have a nice thump trill

if you do swap in the megaphone love to hear it tho! Definitely wishing you luck!

im still trying to figure out what the stock exhaust inside diameter is and going back and forth about deleting the resonator ?

 

[Victorofhavoc]

If it’s not a boxer 4 or a v4 best you can hope for is “good”

great on a turbo inline 4 isn’t easy.
I’ve heard i4’s with megaphones and they sound great. But those motors are aided by nice flowing heads, decent headers and liter bike cams at high rpm have a nice thump trill

if you do swap in the megaphone love to hear it tho! Definitely wishing you luck!

im still trying to figure out what the stock exhaust inside diameter is and going back and forth about deleting the resonator ?

I've got mine off and sitting in my basement. I can measure the ID for you on Sunday.

 

[UWU-mancer]

I've got mine off and sitting in my basement. I can measure the ID for you on Sunday.

Bro I would super appreciate that. Thanks!!!

 

[Victorofhavoc]

Bro I would super appreciate that. Thanks!!!

Finally was able to do this and the forum is back up... 2.25" inside diameter measured at the very front of the exhaust by the 3 bolt flange.

 

[UWU-mancer]

Finally was able to do this and the forum is back up... 2.25" inside diameter measured at the very front of the exhaust by the 3 bolt flange.

Thnx!!!! That’s surprisingly small. I thought it would’ve been at least 2.5”

I appreciate u

 

[Victorofhavoc]

Thnx!!!! That’s surprisingly small. I thought it would’ve been at least 2.5”

I appreciate u

The factory downpipe I believe is 3" od. Then it restricts down at the front pipe before the "catback" section. Heat coming out of a turbo is huge, and will cool at a faster rate compared to NA. Combined with the turbo consuming some of the energy there's less of a need to size up the exhaust further down. As it cools it needs less space to maintain the same flow rate/velocity. You won't benefit from a larger exhaust anywhere in that section, and probably not at the front pipe either. If the turbo was made larger or was pushing significantly more exhaust volume (like on e85), you'd want a much larger pipe right after the turbo... Once you get past the downpipe, you again wouldn't need as large of a pipe, even with e.

Exhaust pipe size will also drastically change tone of the exhaust. Especially if you're sizing up, then down, then up again. This is often what causes the "fart cannon" sound on 4cyl engines that people hate.

 

[TonsterPS]

The factory downpipe I believe is 3" od. Then it restricts down at the front pipe before the "catback" section. Heat coming out of a turbo is huge, and will cool at a faster rate compared to NA. Combined with the turbo consuming some of the energy there's less of a need to size up the exhaust further down. As it cools it needs less space to maintain the same flow rate/velocity. You won't benefit from a larger exhaust anywhere in that section, and probably not at the front pipe either. If the turbo was made larger or was pushing significantly more exhaust volume (like on e85), you'd want a much larger pipe right after the turbo... Once you get past the downpipe, you again wouldn't need as large of a pipe, even with e.

Exhaust pipe size will also drastically change tone of the exhaust. Especially if you're sizing up, then down, then up again. This is often what causes the "fart cannon" sound on 4cyl engines that people hate.

First post on here, and just wanted to say thanks, this was super informative.

 

[Justpassedu]

so has anyone bought this yet for the Type S that can show a few images and results ?

 

[Victorofhavoc]

so has anyone bought this yet for the Type S that can show a few images and results ?

I realized yesterday the factory exhaust has a megaphone past the middle muffler

 

[Justpassedu]

I realized yesterday the factory exhaust has a megaphone past the middle muffler

Interesting , I have not seen it in any pics. I been debating on removing a resonator or going with a exhaust. I don't want a ton more sound , just a little something more.

 

[Victorofhavoc]

Interesting , I have not seen it in any pics. I been debating on removing a resonator or going with a exhaust. I don't want a ton more sound , just a little something more.

If you just poke your head under, after the center muffler the pipe expands gradually and then flattens to the end of the tip. That's a megaphone. I guess you could buy someone else's outer tip and weld it on in place of the factory center and that would take the pitch up slightly like aftermarket megaphones intend.

I went back to stock exhaust last night. I absolutely love the way the borla sounded. In comfort it was fantastic for putting around town or driving with the windows down through the city. In sport is was absolutely perfect for hearing it and having some fun. Sport+ was a little embarrassing in traffic because of how artificial the its pops are, but it was a hoot on your own or on track. Going back to stock I feel like I'm now driving a prius .

One major annoyance in this car for me is that the exhaust valve is tied to the throttle response mapping. That's fine for stock, but with a loud exhaust sometimes you want it to be quieter and still have the throttle response...that can't be though.

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