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What do you guys think of the notion that an aftermarket catback w/enlarged pipes isn't a good way to approach our exhaust? With only the 1.7L, unless you're boosted I think the pipe diameter is probably just fine. I would think you'd want to attack the biggest sources of restriction, the cat and the muffler. The EX header seems to be pretty good especially compared to DC.

I'm thinking of just running the stock EX header (or an inexpensive ceramic Megan or OBX) random tech cat, all stock pipes and then a hi-flow muffler.

I'm thinking this will be less expensive and "out-perform"--granted we're talking small gains--the h/e set ups I see so many people with.

The freeing up of back pressure from the improved flow with the cat and muffler alone then adding larger dia. piping I suspect may just end up losing torque.

 
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Im geting my turbo soon so my catback doesnt count!

 
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i personally think your better off with the dc header since its very similar to the EX OEM but with smoother curves and bends which may result in better flow.
as for the cat converter, u can gut the OEM one and save bucks. not a good idea though if you have to go thru smog and emission.
if you dont know yet, the stock pipes are 1.75" or very close to that diameter. goodluck and let us know how your exhaust set-up goes

 
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i wouldnt spend much time on the exhaust but to save the money and wait till u get a turbo and do it all at once.

 
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This has been discussed and debated. I have a Kamikaze header, no cat, stock resonator and mid-pipe, and HKS Hi-Flow. I experienced a noticeable (but not huge) HP gain and no loss of low end torque. HKS also concluded stock mid-pipe is proper diameter for NA setup. I don't plan to boost anytime soon.

 
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I know similar topics have been discussed such as stock vs catback etc, but not specifically this set up...if it has sorry. I want to stay smog legal so I'd be keeping my cat...I have over 50k now so I can swap the stock one out. I've seen the posted pics of aftermarket headers vs stock and though I don't see a big difference, I'd definitely consider DC. I thought I'd read that the stock piping was 1.75". I haven't seen any chart or program online to calculate the proper diameter for motor to maximize flow w/o giving up torque but I gotta think it's close especially once you free up the header/cat/muffler. I don't have much experience working with piston motors with this small of displacement.

No offense to those boosting their D17s but for the money and for the performance you get, I just don't think the D17 is a very good starting point....just my opinion. I'll admit I was looking hard at Dezod's kit once the price came out but I bought my Civic as a second car whose job it is to do my highway commuting miles, get great gas mileage and not be a fuqing pig to drive. It's a suprisingly fun little car and while being able to add so much boost with no internal changes is impressive, I'm just not going there....

 
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Whenever you increase the size of the piping you typically lose some low end torque due to the decrease in back pressure. This is especially felt in engines that make low amounts of torque like our D17's. In a V8 engine that makes a crap load of torque its not that big of deal.

 
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that's what I was thinking....you often see our cars with 2.5" piping...that is the same size as what you'll find with performance V8 exhausts....I worked with I5 turbo'd Audis in the 90s and I think the piping was about 2". Early rotaries had big pipes stock but they have little torque at the low end anyway, no cat, and a comparatively huge capacity for fuel and exhaust.

 
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Typically when racing though at the track, low end torque for our cars means absolutely nothing since we typically launch at high RPM's. We are never in the low RPM's when racing so anything that gives us high end power is more useful then torque. I think thats why people tend to go with larger diameter piping to get that high end power.

 
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Rs*r

 
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what do you plan to do with the car?

if you just want a little more kick and make driving become more enjoyful, you can always go with 2" custom piping if your staying n/a? most aftermarket catback exhaust are 2.3"-2.5" sized piping which may not be neccesary. what scansel912 stated above is true, most exhaust were meant for mid-high end power and not low. you may notice your low end is loss but the high end is somewhat increased.

instead of watsing money on a dc header (250$), take apart your OEM ex header and clean it inside out. im not sure if it has oils to protect the coating inside, but u can always lube it which may help performance?