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Discussion Starter #1 (Edited)
I've been running my R18 with no muffler recently and think it sounds amazing so I thought I'd get a sound clip for you guys. Very deep tone. Absolutely none of that high pitched raspy sound. A bit of drone but It doesn't bother me. Subtle bliss of backfire rumble when letting off between 2.5k and 3k rpm. If you're going about 3mph, clutch in and give it a quick blip it'll give you a loud gunshot backfire, it's amazing. :woowoo:

It's sort of loud but it's so low end it's not really a head turner unless you're in a parking garage or downshifting. The video is a really good representation of what it sounds like in the cabin.

Two 12mm spring bolts and she's out. Let me know what you guys think! Fast forward to 2:50 for a pull.

 

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You have the video set on 'private.' Make it public so we can see it.
 

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Discussion Starter #3 (Edited)
Thanks for letting me know, I set it from private to unlisted so you should be able to access it with the link now.
 

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Awesome!
 

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Dang, that sounds about perfect.

I'm not sure I like that much volume with an AT, though. It's an easy enough experiment, though. If it sounds good, I'm sure I can have a piece of pipe, maybe in the 2.5 to 3" range, bent to fit over and onto the cat pipe, and exit where the stock muffler does.
 

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Discussion Starter #7
Dang, that sounds about perfect.

I'm not sure I like that much volume with an AT, though. It's an easy enough experiment, though. If it sounds good, I'm sure I can have a piece of pipe, maybe in the 2.5 to 3" range, bent to fit over and onto the cat pipe, and exit where the stock muffler does.
It's a five speed manual tranny :eusa_dance: I pretty much rev match every time I slow down, It's amazing.
 

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Any issues with loss of backpressure or anything? usually with these kinds of mods you lose a lot of your low down torque and suffer worse fuel economy as a result
 

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Discussion Starter #12 (Edited)
Any issues with loss of backpressure or anything? usually with these kinds of mods you lose a lot of your low down torque and suffer worse fuel economy as a result
There is no noticeable difference in drivability other than the aural pleasure. Regarding loss of back-pressure there is a slew of misinformation floating around car forums. The video I'll link will clear up some of those misconceptions you and others may have. If you have seven minutes I'd recommended everyone watch it, especially at 2:25 when he talks about the pressure differential created by the pulses of exhaust gasses and how the low pressure "dead time" between exhaust pulses helps suck out the gas from the cylinder (called exhaust scavenging). Also his entire channel describes the mechanics of cars from a physics perspective in amazing clarity so I can't recommend him enough.


In short, no restriction in the exhaust system is a good thing. When people de-cat their exhaust they almost always op for a larger diameter pipe as well. When they do that there are then two variables to consider instead of isolating one and concluding its effect. They attribute the loss in low end torque to the de-catting, when in reality the loss in low end torque is because they increased the pipe diameter and reduced their low-rmp Exhaust Scavenging (see video). Smaller diameter pipes yield higher velocity gases and therefore a greater pressure differential to draw out gases from the cylinder. Larger diameter pipes yield lower velocity gases and therefore less low-rpm exhaust scavenging but when in the higher rpm, as you all know, allow massive amounts of gas to be exhausted in which case exhaust scavenging is not necessary.
 

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I just did this.. It's pretty obnoxious with an auto trans LOL
 
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Discussion Starter #14
I just did this.. It's pretty obnoxious with an auto trans LOL
You're right, my friend did it in his auto and it just didn't sound right.
 

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are you running with a muffler delete or just straight up unbolted axleback? i completely unbolted it a few months back and it ended up melting the plastic shroud
 

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Discussion Starter #16 (Edited)
are you running with a muffler delete or just straight up unbolted axleback? i completely unbolted it a few months back and it ended up melting the plastic shroud
That plastic piece was my only doubt in unbolting it. I just went out and checked right now and nothing's been melted. My only guess is if you are lowered the gases no longer pass over the control arm and instead run right into it. I live in the bay as well so I wouldn't attribute it to the weather.

An option for anyone wanting to avoid this would be to find an old 8th gen oem muffler at a junk yard for ~$10. I would cut off the actual muffler from the rest of that piping and just bolt on that piping so that it bypasses the control arm.
 

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Blues Clues
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i actually had a Si axleback from a '09 Si lying around. ended up selling it to another 9thgen r18 and it was a direct fit. i thought about just getting a straight pipe welded in place of my muffler but debated on whether or not i should invest in a aftermarket cat-back system instead. Which part of the Bay are you from anyways? are you in the bay area civic group on facebook?
 

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Discussion Starter #18
i actually had a Si axleback from a '09 Si lying around. ended up selling it to another 9thgen r18 and it was a direct fit. i thought about just getting a straight pipe welded in place of my muffler but debated on whether or not i should invest in a aftermarket cat-back system instead. Which part of the Bay are you from anyways? are you in the bay area civic group on facebook?
I'm in Fremont and also on the facebook page. Haven't seen a single modded 9th on the road yet, but I'm looking forward to one of these meets.
 

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are you running with a muffler delete or just straight up unbolted axleback? i completely unbolted it a few months back and it ended up melting the plastic shroud
Evidently Leopards knows what you are talking about, but I don't. :shrug:

If you completely unbolt the axleback, what does that mean? Does that mean unbolt the axleback from cat pipe and let it hang? Unbolt it ans space it away? Remove it entirely? How does it melt any plastic?
 

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Blues Clues
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the portion of the exhaust system that is the muffler and muffler tip can be taken off with two bolts. it's called the axle-back because its technically the part of the exhaust system that is from the axle and back(to the end where exhaust fumes exit). The axle-back is connected to a midpipe where you would find the resonator of the exhaust system. the cat-back (at least for the r18) is close to the header/downpipe area and is basically the catalytic converter and back. the picture i posted above is the effect of me unbolting the axle-back for a couple months. without a way to redirect the hot exhaust fumes from under the car they were blowing against this lower control arm and melted a plastic shroud covering it.
 
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