A car engine is a living, breathing, organism.

Ok, one of those is true, it’s obviously not actually a living organism, but it may as well be. Your engine needs to breathe in order to do its job. It also needs to exhale. In this blog we focus on the 2022 Civic Si and its exhaust system. Let’s dive in.

Take a look at the OE Downpipe below. The inlet of this component is about 82mm inner diameter. The exit is about 52mm with a rolling lip that opens up to about 58 mm. That’s quite a reduction!!

Notice below, the 2022 EX downpipe and 2022 Si Downpipe are exactly the same.

Let’s continue on to the next pipe, known as the front pipe. The inlet inner diameter for the front pipe is 58 mm. This makes sense since the downpipe and front pipe connect here and smooth flow of air is a basic design concept. Moving on, the exit diameter of this pipe is about 54.5mm. Can you see a pattern here?

Continuing down the exhaust system we call the next section the mid-pipe. We say section because after the front pipe the rest of the OE exhaust is one piece all the way to the tips!

Aftermarket exhausts come in multiple pieces so we need to give these pieces names. We call this first section the mid-pipe.

There really is only one thing to notice in the mid-pipe, a resonator. Most OE exhaust resonators dissipate noise effectively, but at the cost of some restriction in air flow. In terms of performance that's a red flag for us.

In the next section we see a muffler on each side meant to further decrease the volume of your exhaust. This is good for those who want a quiet grocery getter but not so good for the rest of us. At the tip, we see a curved pipe to tip design that we speculate is to decrease the noise, vibration, and harness (or NVH for short) of your exhaust. More on that later. But with more curves and bends in your exhaust, it becomes more restrictive as well.

Friction factors or coefficients become higher in pipes with many bends and redirections.

We call this section the axle-back. It includes both mufflers and the exhaust tips.

Now that you can visualize the stock exhaust of the 2022 Civic Si, let's dig deeper.

Your engine is “exhaling” into a pipe that is decreasing in size. In a sense this is good for your in-cabin comfort but your engine doesn’t feel the same. Imagine running a marathon and not being able to breath out through your nose properly. Or when you are feeling ill, you have one nostril clogged and the other sort-of free, that’s a good comparison of how your engine is probably feeling. Besides, you can’t hear anything!! Remember folks, loud pipes save lives!

Now, what about this business with NVH? It’s basically feedback you get from your car that is literally noise, vibration, and harshness. Perhaps you can’t hear your passengers speak and the panels are buzzing, that’s NVH. Sometimes there is a boom in the cabin. Honda puts a lot of work into minimizing these things. They’ve taken it so far that it reduces performance and the driver loses some connection with the car. We have noticed NVH is definitely more pronounced in the 2022 EX when opening up the exhaust because of its CVT transmission. The Si has a manual transmission so NVH isn’t as much of an issue, but one to still keep in mind.

To conclude our discussion, it’s pretty obvious that there is room to improve the exhaust for the 2022 Civic exhaust. This is true not only in performance, which is our top priority, but also the sweet, sweet sound we get from that turbocharged 1.5-liter engine.

How well can we get these engines breathing? How well can we get them to sound? Find out in the next blog.

And with that we leave you ‘till next time.

Thanks for tuning in with 27WON Performance. I DARE You to REDEFINE the Aftermarket

-Josh

11th Generation Si Exhaust - OE Breakdown - Design Blog Pt 1.