Greatness Takes Time, 2017+ Civic Si Performance Exhaust Pt.4

In our last update on the 27WON Civic SI Exhaust, we asked our readers to tell us if V3 was the preferred design over V2 or V1. Your feedback was tremendous and consistent; V3 was the overwhelming winner. We immediately got to work on the next step in product development; can we even make this?

It was one thing to design these unique tips specifically for the SI using Solidworks CAD modeling but it’s a whole other level of difficulty to actually physically produce them. We have to admit, manufacturing this design is proving to be a challenge. But hey, nothing worth doing is ever easy!

Here is the fruit of your awesome community feedback and our elbow grease to make it happen:


Each tip is a combination of laser cutting, forming, welding, and polishing;

thus they are very labor intensive to fabricate. The results are like nothing else on the market. We haven’t been this excited since the day we picked up our 2018 SI Sedan!

You can see why the 27WON Performance SI Exhaust will be worth the wait.  


While we continue working hard on bringing the 2017+ SI Exhaust Tip design to market, we wanted to take a moment to stop and be sure to educate the community about the unique design of our 27WON Performance exhaust. We’ve always believed in educating ourselves and the community alike and we strive to be an exceptional resource for both experienced and new Honda owners.


There is more to the upcoming SI exhaust than ‘just the tip’. Our SI exhaust shares features with our Civic HBS exhaust.

The most unique and thought-provoking feature of the 27WON Civic exhaust is the side-branch resonators located on the “axle-back” section of the exhaust.

We often hear questions like “Why are there long curled pipes on the exhaust that appear to go nowhere?”

These pipes are not just for looks, they have a very specific and important job to perform. 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 noise called "drone" that can ruin an amazing driving experience. I think most of us can at least 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 canceled out, but they only work in a very small window of frequencies. This is why our exhaust has two pipes of different lengths. The sound travels up the pipe then hits the dead end and bounces back. This is always happening despite the frequency. For certain frequencies, the waveform bouncing back is exactly equal and opposite to the waveform entering the pipe. When this happens the waveforms cancel out, eliminating the drone. It’s actually almost spooky how well it works. 

The 27WON Civic exhaust design was tuned specifically for the L15 EarthDreams engine; we tuned our exhaust to cancel out an excessive drone around 4100rpm that is prevalent on engine deceleration and also to cancel out drone around 3000rpm where a majority of highway cruising will occur. 


The best part about the 1/4 wavelength resonators is that they don’t sacrifice any of the exciting noise on acceleration (which is where we really want to hear and exhaust) nor do they have an effect on power.

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

Thanks for tuning in, you can catch more info on the 27WON Performance Exhaust in a few weeks.