Hey guys I知 looking for some help here I知 trying to put in a custom exhaust set up on my 2012 fit I have to keep both Cadillac converter壮 but would like to do a straight exhaust right out to the back of the car but state of Maine Cumberland County laws states that I have to have a Cadillac converter and a muffler. But I知 trying to go with a sleek low profile muffler that gives me the full sound of the engine

 

The "catalytic" converters in your car house the oxygen sensors that are part of your smog and computer systems. The primary oxygen sensor monitors your air/fuel ratio that keeps your engine running smoothly and the engine pollutants at a minimum. The secondary oxygen sensor monitors the efficiency of the catalytic converter and makes sure it's running properly and is burning off pollutants before they pass through the converter and out into the atmosphere. If you eliminate the catalytic converter and oxygen sensors, the computer would not have the signals it needs to adjust the air/fuel mixture of the engine. Without those signals I don't know if the computer system would even be able to keep the engine running.
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If you're just looking for a deeper sound in your exhaust try doing a search on this forum about doing a replacement catback system, and see what fits your goal. There should also be some sound bytes on Google as well, from those that have modified their exhausts with catback systems.

 

I'm not for ditching all the noise management gear, but I've read about o2 sensor spacers that push the sensor back out of the line a little more and make it read like everything's cool. Seems kinda sloppy, but readily available on amazon with a slew of positive reviews.

 

It's true some owners that are having issues with check engine lights that are oxygen sensor related use those adaptors to pull the oxygen sensor back out of the direct air/fuel exhaust stream to trick the computer into shutting the cel code off. But if you remove the catalytic converter and oxygen sensors all together, like I suggested in my first post here, it's a whole new ball game. I don't believe the car's computer could keep the engine running if there was no oxygen sensor feedback to the computer to establish an air/fuel ratio.

Since the op doesn't have the oxygen sensor issue now anyway, I suggested he not remove the catalytic converter or oxygen sensors in an attempt to change the tone of his exhaust. It makes a lot more sense to make changes after the catalytic converter by installing a cat back system.

 

Did this on a old Civic beater car: replaced the catalytic converter with an aftermarket one because the OEM was shot, but I had a CEL for catalytic converter below threshold. To get rid of it, used an O2 spacer. Did the trick. Don't know if this works without any catalytic converter. Would not recommend to not run any catalytic converter thought.

Your best bet to a better sound and not destroying the environment is a catback exhaust along with an intake.

 

I agree with you guys whole-heartedly. Certainly wouldn't recommend a cat delete, but was attempting to suggest that it could be done and how one might accomplish it.
Motorcycles and other small motors run without o2 sensors. I actually added a wideband o2 from Innovative Motorsports to my bike's exhaust so that I could install a lambda/AFR guage and more accurately tune its carburetor.
I understand that they (o2 sensors) are used read, as the name implies, the amount of oxygen left in the exhaust by measuring temp difference between parts of the sensor. The ecu uses the info to adjust fuel and maintain to the best of its ability the ideal air fuel ratio determined by the manufacturer.

​​​​​​It's a good system. If one were to remove it or operate a vehicle that never had it, well, said vehicle would just put in whatever fuel it puts in for the current throttle position and not be able to adjust itself for efficiency. Eh, here's a youtube video where someone explains it better.

Folks can work around the system though, as some do. I think they buy "test pipes" to do so. I believe their name comes from ability to compare to a functional catalytic converter. O2 sensors are retained to avoid throwing codes. I don't know if in practice there would be some complications, because o2 sensor readings are based on temps, and (don't quote me) the downstream o2 should see higher temps than the upstream as a result of resistance to exhaust flow generated by the cat/s. Maybe they account for that on test pipes and have some means to address the issue, like using a spacer/taller bung on the upstream o2, but I really don't know. There should certainly be a way to make such things work though.

I can say from experience that if one simply unbolts the exhaust line post-header, or runs straight pipe, there will be hearing damage and a notable loss of low end power.

As the other guys have mentioned, a different muffler would be the way to go, but dont throw out your stock one! Keep all your stock parts, damn it! Or mail them to me.

 

That's what I did with mine....Tanabe Medallion cat-back exhaust and an HPS short air intake. (which made switching to a 51R battery a no-brainer)
I really like the sound. I didn't want a loud raspy, tin can sound.....and it isn't.

 

Had that same exhaust on my racing Civic with an ITR motor. That is a really great and quality exhaust. Not too loud too. Never had any problem with the cops with it.

And of course, with the intake, not reason not to go with the 51R battery. It is a win-win!