OFFICIAL 2017 Civic Si Exhaust Thread

danny185

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Try just the muffler first. It really gives a smooth mellow sound. I plan on doing a DP/FP at some point but I’m loving the sound now. The DP/FP will just be for performance and a custom tune at some point.
I did the muffler delete and it sounded awesome!!!!

Now I installed the PRL downpipe and the rasp that was on reverse you will hear on 1st and second it sounds awesome. Now it was lou as Heck! So I ended putting another resonator!

I will have it like this until I buy the Thermal exhaust!!
 

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MAP is working on a catback with multiple exhaust tip choices all the way up to four tips.
It will have different color tips as well.
 

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For those who now have an aftermarket catback and have your stock system off to the side collecting dust, can you tell me the dimensions of the stock resonator? I have a Magnaflow catback and it is too loud and won't pass my state emissions. I want to replace my Magnflow resonator with a Flowmaster DBX. The DBX is 6" but the Magnaflow on there now is 5". I want to see if a 6" muffler will fit. Length is not a problem at 14". Thanks all!
 

LoneStarFlatLanders

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I had the resonator delete done by a local muffler shop. Cost me $64.67 and I kept it in case I ever wanted to put it back on. Sounds great. Slightly louder with a deeper tone. Couldn't be happier.
 

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I had the resonator delete done by a local muffler shop. Cost me $64.67 and I kept it in case I ever wanted to put it back on. Sounds great. Slightly louder with a deeper tone. Couldn't be happier.
Just the resonator? Still have the OEM mufflers on?
 

LoneStarFlatLanders

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Just the resonator? Still have the OEM mufflers on?
Yes. I was afraid of drone and it being too loud with the mufflers deleted also. I made my decision after listening to the videos earlier in this thread. For me, the resonator delete was loud enough. However the guy that did the work said that they deleted a lot of mufflers on these cars but never the resonator.
 

bahndrvr

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I had the resonator delete done by a local muffler shop. Cost me $64.67 and I kept it in case I ever wanted to put it back on. Sounds great. Slightly louder with a deeper tone. Couldn't be happier.
I have DP/FP stock Resonator and a exhaust and put a 12" glasspack in front of the stock resonator, sounds perfect! The cold start was waking my wife and youngest daughter everyday so I compromised and added it but now I love it! I will eventually go magnaflow as I prefer that sound but this is perfect for what it is!
 

brandonduley

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97F5733B-7ECE-4150-A45E-C52FA2A1155B.jpeg
Got the Magnaflow catback exhaust delivered today, pulled the stock one off my 2018 Civic Si Sedan, started installing the Magnaflow kit and ran into a fitment issue with the inlet pipe to the stock catalytic converter. Seems the bolts/studs that are attached to the stock cat are not long enough to pass through the Magnaflow flange and allow the nuts to fully engage. One of the nuts does fully engage but is flush the end of the bolt and as seen in the picture, the left one fully tightened doesn’t even accept the full nut.

Any suggestions? Are these threaded studs? I didn’t feel anything on the backside of the stock cat that would make me think they are bolts that could be removed and replaced with something longer.
 

hawk02

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97F5733B-7ECE-4150-A45E-C52FA2A1155B.jpeg
Got the Magnaflow catback exhaust delivered today, pulled the stock one off my 2018 Civic Si Sedan, started installing the Magnaflow kit and ran into a fitment issue with the inlet pipe to the stock catalytic converter. Seems the bolts/studs that are attached to the stock cat are not long enough to pass through the Magnaflow flange and allow the nuts to fully engage. One of the nuts does fully engage but is flush the end of the bolt and as seen in the picture, the left one fully tightened doesn’t even accept the full nut.

Any suggestions? Are these threaded studs? I didn’t feel anything on the backside of the stock cat that would make me think they are bolts that could be removed and replaced with something longer.
Did it come with replacement bolts? I remember someone saying the studs can be banged out and replaced with bolts, they are pressed in studs from what I've read....or you can get nuts like the ones that come with the 27won where they recess into the flange to grab more threads if the holes on the magnaflow flange are slightly larger than the studs are.
 

brandonduley

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Did it come with replacement bolts? I remember someone saying the studs can be banged out and replaced with bolts, they are pressed in studs from what I've read....or you can get nuts like the ones that come with the 27won where they recess into the flange to grab more threads if the holes on the magnaflow flange are slightly larger than the studs are.
It did not come with new bolts. Instructions stated to re-use stock hardware.

Waiting to hear back from where I purchased to see their suggestion on the situation before pounding out the threaded studs.

Will also check into the 27won route. Can you buy just the bits from them?

Thanks for the reply.
 

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97F5733B-7ECE-4150-A45E-C52FA2A1155B.jpeg
Got the Magnaflow catback exhaust delivered today, pulled the stock one off my 2018 Civic Si Sedan, started installing the Magnaflow kit and ran into a fitment issue with the inlet pipe to the stock catalytic converter. Seems the bolts/studs that are attached to the stock cat are not long enough to pass through the Magnaflow flange and allow the nuts to fully engage. One of the nuts does fully engage but is flush the end of the bolt and as seen in the picture, the left one fully tightened doesn’t even accept the full nut.

Any suggestions? Are these threaded studs? I didn’t feel anything on the backside of the stock cat that would make me think they are bolts that could be removed and replaced with something longer.
I have a coupe and did not run into the same issue. I wonder if there is anything different about the sedan? I am sorry you are having trouble. To be honest, the Magnaflow is a disappointment. It drones a lot which was unexpected based on past Magnflow systems I had. Based on my experience, Magnflow customer service is basically non-existent. I have left 2 voicemails and emailed them and they never replied. I just needed more detailed info on their specs so I can best pick a strategy to quite the system down. I ended up getting a small muffler that will mount between the resonator and muffler section. I hope you can get a hold of Magnaflow and see what they have to say. Sorry I can't offer any good info for you. I hope you get it resolved.
 

hawk02

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I have a coupe and did not run into the same issue. I wonder if there is anything different about the sedan? I am sorry you are having trouble. To be honest, the Magnaflow is a disappointment. It drones a lot which was unexpected based on past Magnflow systems I had. Based on my experience, Magnflow customer service is basically non-existent. I have left 2 voicemails and emailed them and they never replied. I just needed more detailed info on their specs so I can best pick a strategy to quite the system down. I ended up getting a small muffler that will mount between the resonator and muffler section. I hope you can get a hold of Magnaflow and see what they have to say. Sorry I can't offer any good info for you. I hope you get it resolved.
This system is listed as their "competition" system and notes an "aggressive" sound level.....with this type of system and this type of car, drone would be a given.......and should be expected. I have had 3 different cars with Mag on them and all were above expectations.
 

hawk02

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It did not come with new bolts. Instructions stated to re-use stock hardware.

Waiting to hear back from where I purchased to see their suggestion on the situation before pounding out the threaded studs.

Will also check into the 27won route. Can you buy just the bits from them?

Thanks for the reply.
Not sure, maybe give them a shout and ask Vincent, they seem like a top notch company and may be willing to help even though it's not their system or at least tell you where you may be able to source the 3 nuts yourself.
 

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