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Hello everyone! This is my first post. I'm planning on purchasing a high mileage 2001 civic hx 5-speed as a second car. I'm getting it solely for the mpg (~40mpg). I already have a "go fast" car, so i'm not looking for any performance gains. However, a deeper exhaust tone isn't bad either. I'm considering an exhaust for the hx for 2 reasons: 1) added fuel economy, and 2) the stock exhaust probably has clogged cats anyway because of the high mileage.

So my question is whether there is a cat in the exhaust manifold and if it is, do all 7th gen manifolds fit the hx? If they do, is everything else interchangeable. such as the O2 sensor locations? Basically i think i'm looking for a header back exhaust for this car, and i'm having a hard time trying to find out information. I live in Illinois so it will have to be smogged (no visual inspection), but i guess i can just have a high flow cat welded in. Any info is appreciated!!! (because there seems to be none out there on the hx)

 
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the hx is a tricky car. there are actually TWO cats and neither should be removed. if you get an exhaust, it will have to be just replacing the piping after the cat, and a muffler. you can replace the cats if you want, but youre looking at well over $1k for them. i wouldnt bother unless the car drives poorly or the manifold turns red hot. in other words, no need to replace expensive parts if they still work. now if you want you could change the oxygen sensors, but those are also very pricey around $250 each i think. converting to a header back and deleting the cats you will never pass emissions. hx does not use a standard cat converter. it has one CO and another NoX cat due to the lean burn engine.

 
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hmmm, well thank you for the input, i've read that one of the O2 sensors is actually a wideband, which is actually pretty cool....anyway, i just figured that if i put an intake & exhaust on it, i may be able to improve gas mileage as well as replace a part that suuuper old. but i guess it its not broke, i won't fix it. its just a bit surprising that other people haven't dont something like this, i mean it is a civic . then again, this is the econo version, so i'm sure that people aren't trying to make this one go fast, but cause that would be a bit of a waste of money IMO

 
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we are talking maybe a few hp here, nothing you would really notice. the car is already tuned very well from the factory. you could add an air intake without problem.

 
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I don't mean to waste space here, but I have NEVER heard of an HX.. until now.

 
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Interesting. The earliest HX I've seen was a 5th gen, I think, but most definitely a 6th and 7th gen iterations. They are/were the most fuel efficient Civic you could buy, outside of a Hybrid model.

My EM2 is listed as ULEV I, where the HX is ULEVII... I think.

 
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Almost forgot half of this thread is about fuel economy:
I'm sure an intake may help a bit. Less restriction and all.

Oh, keep your car as light as possible. Don't go driving around with a set of golf clubs or dead hookers in your trunk. Clean out your car and go on a diet. Every little pound helps. In all seriousness though, keep the interior cleaned out of heavy objects.

Proper tire inflation can help a bit too as well as regular maintenance. Specifically oil changes. Keep on top of that and you are golden.

If you are looking to drop some cash: Check out some lighter wheels maybe. Check the weight on a carbon hood/trunk. Could save a few pounds. Throw some paint on top and no one would know. Aftermarket suspension could be a bit lighter as well when compared to the stock setup.

Hopefully all of that made sense. I'm rambling a bit today.

 
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I like your advice! I'm considering losing weight so I can take off faster . I know it sounds funny but there is a VERY noticeable difference when I have a friend in the car who weighs as much as I do as opposed to when it's just me in the car.

 
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yeah, i'm looking for fuel economy gains and considering the factory exhaust is 1.7" in diameter, thats GOTTA be really restrictive. However, i'm sure the engineers at Honda knew what they were doing. Once i finally get the car (got it from a dealers auction) i'll assess all the mechanicals. I'll definitely look at some lighter weight rims and maybe a carbon fiber hood. Thanks for the advice! btw, anyon eknow the weight of the HX rims??

 
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If not in here, search in the internet like i did
http://www.wheelweights.net/

 
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i think the 2001+ hx got screwed in the weight reduction dept. the rims are nearly 14lbs which is okay, but there are much lighter. older hx had 12 lb rims and the older vx had even lighter rims but smaller. the newer hx is overall much heavier due to all the extra stuff they added.