Recently we've been working on developing a custom alternative to the OE Honda exhaust found on the 2016+ Civic Hatchback Sport. 

It has some interesting design aspects and style, but in the end it leaves a lot on the table in the style and performance categories. In this post we are going to dive into the design of the 27Won Performance Mid-Pipe Back exhaust system and show you the method behind the madness.

When we design an exhaust system, we approach it with four critical goals in mind: Installation, Fitment, Style, and Performance.  If any of these aspects are missing or lacking then we have not hit mark on the design and will continue to develop and refine. 

First let’s dive into installation and fitment as they go hand-in-hand. 

Fitment is intuitive in the auto enthusiast community; the performance part needs to fit and fit great.  It’s just that simple. There’s nothing more frustrating than finally getting the performance part you’ve been working so hard to purchase just to find that it doesn’t fit. Now, perhaps the less intuitive goal here is installation. When we say installation, what we mean is making it easy for you to install your new parts. Along with proper fitment, the parts need to have clear and concise installation instructions and all the necessary hardware to get the job done. Let’s see how these come together.

Unlike some aftermarket exhaust systems out there, the 27WON exhaust exclusively uses thick 3-bolt flanges at all connections with a multi-layer steel gasket. The flanges are laser cut and TIG welded for an exact fit with the provided stainless hardware. However, these don’t take care of the biggest pain point with the Honda OE exhaust: those damn studs that connect the mid-pipe to the rearward exhaust. 

With the thick laser cut flanges, we quickly realized that the OE studs are not long enough for proper thread engagement, and to make things even more challenging: they are welded in place so removing them was not an acceptable option. 

With that in mind, we designed a simple solution that requires no extra effort for you:  If you can’t extend the stud then extend the nut. We increased the diameter of the holes in that specific flange and designed step nuts that allow the thread to engage across the entire stud through the flange. Simple, effective, and you don’t have to modify an OE part that you may need in the future. 

Next up is style! 

It's a given that the exhaust system needs to look great under the car and from the back. 

The entire exhaust; piping, flanges, and hardware are manufactured from T304 stainless steel for its durability, reliability and great looks once polished. The exhaust tips are large dual wall design with a 10 degree slant cut exit to follow the natural lines of the car with an ID of 80mm expanding out to an OD of 100mm for the outer wall. Lastly each tip has stamped logo plate welded to the outside faces. 

Now you are probably biting at the bit wondering about the unique design of the rearward axle-back section. 

Not only is this a very interesting design that screams intention and purpose, but it’s functional. Let’s dive into that next...

Lastly, we have performance.

This can be broken into a few different categories: audible, weight and power. 

For the sake of not overwhelming you with too much information, we will cover just audible in this post and pick up weight and power in the next blog.  (Patience is a virtue right?)   

Why are there long curled pipes on the exhaust that appear to go nowhere? 

These dead-end pipes are called “side-branch resonators” or also commonly known as "¼ wavelength resonators".  Their purpose is to filter out specific frequencies that cause an excessively loud humming sound called "drone" that can ruin an amazing driving experience. I think most of us can at least once recall being in a car with such awful drone that it made us want to jump out of the door on the freeway. 

The most critical aspect of these pipes is the length. Controlling the length of the pipe allows the exact target frequency to be tuned and cancelled out, but they only work in a very small window of frequencies which is why our exhaust has two pipes of different lengths. The sound (waveform of the sound) travels up the pipe then hits the dead end and bounces back. This is always happening despite the frequency, but once the correct frequency is met, the waveform bouncing back is exactly equal and opposite of the waveform entering the pipe. When this happens the waveforms cancel each out, eliminating the drone. It’s actually almost spooky how well it works. 

For this particular piece, we designed our exhaust to cancel out an excessive drone discovered around 4100rpm that was prevalent on engine deceleration and to cancel out drone around 3000rpm where a majority of highway cruising will occur. 

The best part about the ¼ wavelength resonators is that they don’t sacrifice any of the exciting noise on acceleration (which is where we really want to hear the exhaust) nor do they have an effect on power.

Yes,  in this case, you can have your cake and eat too. 

Thanks for tuning in, you can catch more info on the 27Won Performance exhaust in the next blog!

-Barett @ 27Won Performance