Dwinthrup

The rear o2 severs not purpuse in adjusting the air to fuel ratio, it's only there to detect that the cat is there and working correctly. If you have no cat you will get a check engine light. You can buy a mil eliminator for like $50 or so, or you can buy spark plug non fouler and a bung to keep the o2 out of the main stream of exhaust and that would be enough to prevent the check engine light. And as far as back pressure on an engine I've heard that to be a myth because it was needed for early carbs, however I doubt that it's a myth. I once pulled the exhaust off of my t-bird for some reason and I had no low end torque, I replaced the exhaust and it was back "mind you that it is straight piped so theres no real back pressure to start with. I found this link for more info: http://www.uucmotorwerks.com/html_pr...torquemyth.htm

ZachsXJ

Finally somebody has some hard facts to back up what they're saying. thank you.

Dwinthrup

I like facts they help prove your point and help settle disbelief...... well for the most part lol.

ZachsXJ

Something like that, and they make you seem like less of a tool who is just talking out his rear end even if you know your stuff. I honestly couldn't figure out why the heck an air pump(AKA an internal combustion engine) would benefit from having pressure to push against to expel air. basically the backpressure helps because the fueling system can't keep up with the amount of air the engine is flowing....how does one fix that? by upgrading injectors of course :P then you can run a straight pipe, make more tq than stock and not burn exhaust valves.

XJ's~For~Life

So the cat does help with backpressure and torque then huh. I just know that I have no where near the bottom end I used to have and it happened after I changed my exhaust. In a Jeep bottom end is more needed then topend power imho. Im kicking around the idea of running a whole new exhaust when I got some money laying around which is mostly NEVER!

ZachsXJ

It only helps if your fueling system can't keep up with the volume of air your engine is flowing. If you have injectors that can keep up you can run a free-flowing exhaust and actually make more tq than stock

XJ's~For~Life

Yea, Pretty much change one thing change em all huh! Well it ran best before I changed exhaust so I guess I will try to go back first and see what happens. I would like to change some things on the intake and air filter and possibly the TB. Then I may need a better flowing exhaust. I just know when it was stock exhaust I could turn over 31" mudders from a dead stop so easy it was crazy. Now with smaller 245/75's it wont spin from a dead stop with it on the floor!

ZachsXJ

No it doesn't. but changing one thing CAN change a bunch of different things. if you have a lack of fuel you make less power and tq. if you are flowing more air than your injectors can keep up with you will have a power loss. I'm not even going to bother trying to explain myself further. the logic is there.

Dwinthrup

So your upset because you can't burn out? I wonder how good your primary o2 sensor is working, are you getting good gas mileage?

You need to be sure that you don't do mods that cause you to run lean or you burn valves, overheat your engine, seize your engine, ect ect. A ecu, pcm, eec, what ever jeeps technical term is for it has to be smart enough to know that you have changed things around.

XJ's~For~Life

Im just saying low end torque from a dead stop that used to equal burn out's. Im saying I could with 31' mud tires before and now im on 245/75/16"s and cant do it.

huntingman2706217

i didnt have a cat before and my single chamber muffer was right where the cat was and exited right there also... i could burn the mess out of 1st an 2nd on 31's and bark 3rd pretty good... but now with my high flow cat... same muffler and 2.5 pipe all the way back i cant bark 3rd and gained more high end... and ive got ford 19lbs injectors and a 01 intake... i now got a hole in my hood with a cone filter right on top of the throttle body... so i know im pulling air and dumping fuel... so i dunno... kinda sucks but gotta be legal...

i dont think i lost any get up and go... just lost low end and gained high end...

XJ's~For~Life

Yeah, I have gained some topend go but bottom end up to 3k or so is just sluggish feeling now where it used to pin you back pretty good. I know one thing that is hurting me is the temp running so cool cuz the engine is not at the best operating temp so its dumping fuel to try and warm it up but dont make it. I just picked up a T-Stat and gasket to put on this week. I also need to put my AC fan on there also. Never needed it with it running at like 150. Only time it saw 195ish is when I offroad it poking around for like an hour.

XJ's~For~Life

Well I got a cat, Just gotta get it put on there. I got the cat with the o2 mounted in the pipe also. Ima put it back on and use my Thrush turbo and run me a side pipe again I guess. I had the best power that way. Still urkes me that I cant turn the tires over on dry pavement. I will update when I get the exhaust back on and test some. Also I replaced my T-stat and it runs about 190-195 like normal now. I checked my throttle body and it was pretty dirty. What would it do if I sanded it really smooth and polished it? Help any? I will get around to making a CAI with a heat shield soon.

I also modded my front bumper and installed some lights. I will get some pics up soon.

huntingman2706217

sea foam man... or take it off and spray it in throttle body cleaner wipe it down... i wouldnt sand it... believe it or not the swirl marks you may end up with can alter your airflow into the intake... i mean you can sand it but then youll have to polish it all out smooth and hope you didnt take more off in one area... cleaning it should be all you need... sandings probly waayyy overkill

XJ's~For~Life

Okay, I have thought about sea foaming the whole thing anyhow. Which hose do you pull off again?