Hi, I have a 04 accord lx as listed above.

I'm taking it in to a custom exhaust shop in a few days to have a flowmaster catback exhaust installed. When I questioned the guy who ran the shop whether I should replace the cat, he said no, do not mess with the cat on an 04 accord. Is this correct? Also, what would a good tip size be for an accord? He recommended a 4 inch? Is there a certain brand that is best?

If anyone here has done exhaust work with the 7th gen of accords, feel free to offer your trials and tribulations or advice. Thanks

 

i personally like the 3 in tip. i have a tsudo n1 exhaust on my 03 coupe and thought that since it was a straight through 2.5 inch it was a bit loud. keep your cats unless you want to worry about the law, cuz i know in cali they hassle you a lot.

 

He was correct on the converter question on two points.
1) The OEM converter acts to control exhaust sound, an aftermarket Converter will allow sound levels that would get you noticed.
2) The OEM Converter has sufficient over-capacity to handle most all that you could possibly throw at it, short of a Turbo.

P

 

Thanks P.
My main question about replacing the cat was for performance, if I needed a higher flowing cat, and I was also aware that the sound would be an issue.

As far as the muffler goes. Will it make a huge difference if I use a flowmaster or order another aftermarket muffler? Because the one that the guy showed me at the shop and another I am looking at online look about the same, and both stainless steel production.

PS. I may have been mistaken, I think it was a 3 inch tip.

 

taken from shawns DIY on everyting 2003 accord(regarding aftermarket cats):

I Would Like Lend My Experience On Some Catalytic Converter Facts & Myths!....
Yes, I bought the $50 special off of eBay for my '03 Accord Sedan 4-cyl (2 poor for a V6), it was a perfect bolt-on fit, came with new gaskets, Very Nice Finish.........It added a decent gain in torque at all RPMs, and provided a nice mild exhaust note when you step on the throttle (this is the very first modification done for speed! no perf. muffler yet) Fifty miles or so and the "Engine Malfunction Light" comes on. (The Owners' manual says this means the emissions detectors have detected a problem) sometimes this means a clogged catalytic coverter or a bad o2 sensor or worse! So I talked to some people and found out about an "Oxygen Sensor Simulator". This item we will call an OSS tricks the computer into thinking everything is ok and the light goes off!!.....HOWEVER,,,,your exhaust will smell like ****, maybe even puff black smoke, and will violate any state's emissions tests. Before I got the OSS There was also other wierd things that happened, at cruising speed my RPMs were higher, idle RPM changed, there was a rattling buzz coming from inside like a cheap muffler makes, Also, it felt like my automatic transmission was shifting at different points, and when floored the shift points were much closer to the redline then before,,,.....6speed users dont care, but with an auto if the computers shift points have changed in comparison to the power band it could make or break a races' finish (Why would I race this 4-door 4-cyl automatic grocery-getter with a car seat in the back, I don't). The downside is the engine is making some of the power by trying to compensate for things it doesn't comprehend, and could lead to serious malfunctions, especially since the o2 sensor was disabled by the OSS, detecting real malfunction are hindered. My car ran especially rich at idle, probably to dilute the oxygen level with gas because of the unmodified o2 sensor. It is your call, but in the end, I put my old cat back on and replaced the pre-muffler with a straight pipe....I got the same mellow low tone and torque all the way across the power band, but with none of the bad side effects the old replacement cat had, and by the way, it isn't really a high-flow catalytic converter, it is a straight-pipe resonator or pre-muffler with a hole in the side for your o2 sensor. If your cat doesn't have an o2 sensor in the center of it then good for you, if it does have an o2 sensor, listen to what I just said and make an educated decision.

 

so basically what ur saying is, the OEM cat is good enough for what im looking for since I'm not going turbo or s/c?

 

Had the system installed today. The tech talked me into putting a dual system in for a little extra cash. Did 2.25' piping and single canister 4' tips. Right when I left the shop the exhaust was INSANELY loud. I felt scared to bring the car over 3k RPM's because the car started to shake. When I got home I put the silencers in and it reduced the noise tremendously.

I'll put pics up shortly.

 

dual exhaust on 4cyl?

 

this might be a myth, but putting an aftermarket dual exhaust on a weak engine could cause it to lose torque. the exception would be if the car were a v6 or the dual exhaust came factory-built. correct me if i'm wrong on this.

 

I didn't think that it would cause me to lose performance.

The fact that it's dual exhaust doesn't make any significant performance gain, although I was not aware it would cause me to lose torque. If anything, I have been feeling power gains throughout the power bands and cut .6 seconds off my 60 time (from 8.2 to 7.6 ). When I talked to the guy at the exhaust shop, he asked me about the v6 in terms of power GAIN.

The dual exhaust was for cosmetic purposes, not necessarily performance.

If the torque loss is true, please let me know.