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Old 09-27-2013, 04:30 PM   #1 (permalink)
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Question Exhaust Choices and Mileage

Hello, world!

So it's been some time since I've been around these parts. I have been cycling the past 5 years, and am just now starting to use a car again. I currently have a 2000 Honda Civic, that will become my daily driver (former best in this same car was 50mpg).

So I noticed my exhaust has a pretty bad leak, just in front of the muffler where it attaches to the exhaust pipe. I was going to look into getting this fixed, but wanted to weigh my options first to see if there may be any difference to be gained here in terms of mileage. I basically have three paths to go here, and was hoping to gain some insight or discussion from the community.

My first thought was to purchase a cheap, aftermarket cat-back exhaust system. This may be lighter and sound ok, but I was concerned the free-flow design may (if it does anything at all) actually lead to less mileage and higher power.

My next thought was simply replacing the muffler with an OEM original cat-back exhaust. This would provide stock power and mileage, and would be nice and quiet.

Going further down this path, I thought about purchasing an OEM style muffler, with a smaller exhaust port than the car came with from the factory. I figure this in addition to a reduced intake port may lead to a leaner burning car, and higher mileage.


I am still really open to ideas at this point, and am hoping someone here may be able to provide some insightful discussion or some personal experiences with exhaust modifications.


Thanks!
Woody

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Old 09-27-2013, 04:45 PM   #2 (permalink)
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This has been discussed many times... here is a guide to some of those discussions: http://ecomodder.com/forum/showthrea...ead-20689.html
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Old 09-27-2013, 04:51 PM   #3 (permalink)
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A free flow exhaust can lead to poorer mpg numbers. I am unsure on other vehicles but on ford 302 motors having a single stock exhaust outlet improves upon low end torque which is what hypermilers love. When improved to a high flow true dual exhaust the low end power disappears but the high end improves 4000+ RPM.
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Old 09-27-2013, 05:17 PM   #4 (permalink)
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The cat back portion of the exhaust is made of multiple sections, so if your leak is coming from around the muffler, you may only need to replace the axle back section. I bought a cheap ebay axle back section and it has served well over the past couple years. The OEM Honda part is double the price.
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Old 09-27-2013, 05:36 PM   #5 (permalink)
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My 96 had that. The pipe coming in to the muffler rusted. I replaced it with a used OEM item. My mileage was good, so I wouldn't mess with it.
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Old 09-27-2013, 05:40 PM   #6 (permalink)
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Oh, and no exhaust will make it run leaner. The O2 sensors read the actual exhaust and the computer adjusts fuel input to match.
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Old 09-28-2013, 08:59 AM   #7 (permalink)
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Thanks for the quick replies everyone!

That's kind of what I figured - the exhaust wouldn't play a noticable part in the overall mileage nor performance of the car.

I had been looking around just for the axle-back section and think I may splurge for something along these lines:
Walker Exhaust 18561 Exhaust Muffler Muffler | eBay
Bosal 163 727 Exhaust Muffler Rear Silencer | eBay


I can tell that the car is due for a general maintenance though - replacing all fluids, filters, spark plugs, injector cleaning, etc. The car labours just momentarily when starting it cold, or when it has low fuel in the tank. I think some new parts may help out in it running efficiently and maintaining it's longevity.


Thanks again for all the level-headed advice guys

Woody
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Old 09-28-2013, 10:00 AM   #8 (permalink)
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While a larger exhaust will not directly cause your car to burn more gas, it will shift the power band higher, leading to less power at lower revs unless you drive with a heavier foot.
advantage is that larger, open exhaust will let you hear the engines tone and you'll know sooner when you are pressing to hard on the accelerator pedal.

There are online calculators that will tell you the correct size exhaust you need for a given RPM and engine displacement.

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