Will straight piping my jeep lead to better mileage or will it just make it loud as crap? When I say straight piping it I mean leaving the cat converter but cutting off the muffler.
straight pipe=better mpg?
87manche17
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Earlier 4.0s only have an o2 sensor on the exhaust pipe off the manifold and do better without a cat than they do with it.
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Well mine being an 88..only 1 02 sensor in the manifold. I must disagree.
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You just said the same thing I did...
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No I meant mine does better with a cat vs without one lol..Emission wise I have more carbon monoxide than with my cat:2thumbsup:
02 sensor and everything is new. But yes only 1 02 sensor. Idk personally I think running straight pipe was too raspy..some like that sound so its all preference. But emission wise it will always be better running a cat! Now performance wise I think a good high flow cat & straight through muffler like a magnaflow or borla would be no better than a straight pipe..a chambered muffler like a flowcrapper or alike then the straight pipe will probably preform better.
Me I liked a deep sounding exhaust...mine sounds similar to this, except louder because its dumped before the axle...I run a magnaflow muffler p#12646. 2.5in/out, round body high clearence so it tucks up nicely..no worries of killing it offroading..cost was around 40 bucks on ebay! Also its full welded vs rolled edges like the dynomax mufflers..no worries of it leaking.
Similar sound here..mines a wee bit louder
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How did you run it without a cat? An open header or straight pipe without anything to help with backflow will run worse, but that's a bad exhaust setup and not indicative of a problem from not having a cat.
The 4.0 is an old motor by modern standards and cat converters hadn't been around long. They weren't mass produced on new cars til the late 70s and didn't become required from the factory til the early 90s. The technology back then was more detrimental to motor performance than it was helpful.
If you understand how a cat converter works and have an older 4.0 you will gain mpg and performance from running without a cat. You will with a high flow as well, but not as much.
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Will on my 89 XJ we have had it like this for a long time and works fine I have yet to have a problem with it and on o2 sensors easy fix just buy a dummy for it it will tell computer every thing is finejhumphrey said:
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On the 87-90 rigs..they are Renix. No check engine light..less restrictive maitenance ect.
In cali..the smog Nazi's I smogged without a cat. Only failed because I had to much CO2. So I got my cat on and passed..they didn't even care about it having a cat, although it came with one.
The newer rigs are more finiky to changes..our older renix ear rigs aren't. Actually our 02 sensor only monitors the fuel trims..if it senses it lean, it'll add fuel. If it senses it running rich it'll pull fuel. On the newer rigs, the 02 sensors monitor fuel trims as well but also monitor for emission, carbon, nox ect. If it senses to much it'll throw codes, may run in limp mode ect!
I could go into depth & make it sound all technical but no need:laugh:
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How did you have less c02 emmisions with a cat? They don't filter carbon.
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Ummm ok..I'm not trying to be a *** or anything but yes they do..stock cats are 3 way conerters...filtering out carbon monoxide (CO), hydrocarbons, and nitrogen oxides (NOx). 3 way cats are on anything 81 & newer. Older cars assuming anything earlier than 1981 run a 2 way cat & only filter CO & hydrocarbons.
Most aftermarket cats are 3 way cats..some are 2 way which is why not all replacements are Cali legal. I'm saying Cali because thats where I'm at but either way, yes cats do filter CO out lol. And without one I failed miserably for high CO & just barely passed for hydrocarbons, NOx levels were ok. 2 days later no change except I finally got my cat welded on I passed with almost 0 emissions across the board, absolutely everything was lower..and I mean litterally 0 across the board.
I don't have a scanner but I can type up how both my test sheets read before & after. 2 day difference..same everything, even gas. Idk where you got the cats don't filter CO out but thats one of their main functions....
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I think it's great that people say "dont hollow out the cat and wreck the environment!" It is possible for a well tuned car to pass emissions without one. And if people are so concerned about the environment then dont yous ever again waste gas by offroading and terin up trees and crap. Oh and dont buy a lift kit, winch, pushbar, bigger tires ect ect either then because those factories that make that stuff put out way more pollution in one day then a hollowed cat would in a lifetime. So stay on the road from now on everyone:laugh:
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ITs not the point of that..its more of less do what YOU can. You can't **** down factories or anything, but why help contribute?
Idk about you but when our local groups go out we do trail maitenance, pick up trash & garbage. Not only on our own specific trail either..We do it because if not then everything will be shut down & we will loose what we enjoy doing. Hell we are close to loosing the almighty Rubicon out here...
Facts are cats should remain on your vehicle, without one your polute that much more! I'm not a greeny or tree hugger but in 10-12 years when my duaghters grown up I'd like her to enjoy the same things I have!
I'm an avid supporter of treadlightly because I'd like to preserve the little bit of OHV lands we have left!
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