demo3k

iTrader: (2)

Hey guys I am going to be getting a new exhaust setup here in a week or so and am getting rid of my cats and going to a true dual setup. Anyway for now it's just going to have the stock manifolds and all still. Will I need to get O2 sims/tuning? I know I will throw a code if I don't but I could care less about seeing a code on the dash, my only concern is performance. Will there be any kind of performance hit by having the rear 02's not being able to read right?

I am going to buy LT headers for it next spring so I was kinda wanting to put off having to get any tuning done until I get those on and then get it all done.

Let me know

chefman's_TA

Possibly.. depends on if the computer detects a "rich condition".. or it'll add more timing to over ride this. You might feel less tq/power downlow. Tuning is a major factor, a good tune, might help also. I have o2's in my setup, LTs ( non emissions) style, duals out the back. http://www.youtube.com/watch?v=LLl-Nt-3KaM

Hope this is of some help

Randy

99DWPTA

iTrader: (10)

i just had em tuned out

jag42420

Yes, you need to get the rear o2s tuned out or you will lose a very considerable amount of power. Your car will run like crap if the PCm thinks your cats have failed. Since you're adding headers later and trying to delay the tune until then (wise choice), you could weld in an o2 bung and 'trick' the sensors until you can tune them out. It's cheap, and easy to do http://www.srtforums.com/forums/showthread.php?t=93604 and has worked for everyone I know that has done it.

o1ls1ssmaro

Ive just got lt's and ory.....no tune no o2 sims......... i get **** gas mileage....... i dont really notice a power loss......car idles and goes through power band just perfect........will a tune and o2 sims make the car run better?.......yes........thats why i have o2 sims in the mail on the way here and a tune appointment set up for next week.

demo3k

iTrader: (2)

thanks for the help guys

jag42420

Trust me, the power loss is there. That's why your mileage is suffering. Sims can/will fail eventually. Sometimes they won't work to start with. Sell them. Get your tuner to tune out your rear o2s. Tuning works forever...

ryanfx

iTrader: (2)

so I'm going to be the first one that actually knows what they're talking about.... sorry

rear o2's have NOTHING to do with engine management. The ONLY thing they are there for is OBDII emission testing. Getting your codes tuned out will do nothing, getting a TUNE for your car (maping new a/fs) WILL help you.

Loochy88

iTrader: (2)

to you guys claiming o2's kill your mileage and power, what do you have to back this up? is this a SOTP claim?

i was under the impression that rear o2's (as ryanfx just said), do nothing except for obdII emissions testing.

i am deleting my cats soon, and i was planning on running around with no sims until i could scrounge up a cheap one on ebay.

o1ls1ssmaro

Maybe i shouldnt have been so brief on my post.....sooo............

A gasoline engine burns gasoline in the presence of oxygen (duh).there is a particular ratio of air and gasoline that is "perfect," and that ratio is 14.7:1 (different fuels have different perfect ratios -- the ratio depends on the amount of hydrogen and carbon found in a given amount of fuel). if there is less air than this perfect ratio, then there will be fuel left over after combustion. your **** will run rich. Rich mixtures are bad because the unburned fuel creates pollution whoop de doo right?. If there is more air than this perfect ratio, then there is excess oxygen. that means you **** will run lean. A lean mixture makes more nitrogen-oxide pollutants, and, in some cases, it can cause poor performance and even engine damage.

The oxygen sensor is positioned in the exhaust pipe and can detect rich and lean mixtures. the engine's computer looks at the voltage to determine if the mixture is rich or lean, and adjusts the amount of fuel entering the engine accordingly.

The reason why the engine needs the oxygen sensor is because the amount of oxygen that the engine can pull in depends on all sorts of things, altitude, the temperature of the air, the temperature of the engine, the barometric pressure, the load on the engine,all kinds of ****.

When the oxygen sensor fails/ or is removed , the computer can no longer sense the air/fuel ratio, so it ends up guessing. Your car performs poorly and uses more fuel than it needs to.
If the oxygen sensor (both front and rear) does not operate normally, precise air/fuel ratio control cannot be performed and emmisions increase.......the key words there...............PRECISE AIR/FUEL RATIO CANNOT BE PERFORMED


HENSE BAD GAS MILEAGE AND LACK OF PERFORMANCE.
i know what im talking about

ryanfx

iTrader: (2)

If you were only talking about the front o2's you would be 10000% correct and I would apologize, but again, the rear o2's have NOTHING to do with how the engine runs. The ONLY thing they do is throw the SES light

jag42420

If the rear o2 on an LS1 does not affect fuel mix when a converter failure is sensed, that's a new one to me. I'm fairly new to LS1s, but have worked on vehicles for 15+ years. Not arguing they definitely do on a LS1, but I know that on other vehicles, when the rear o2 senses cat failure the PCM commands the mix to richen and your mileage goes to ****. Front o2s always contol mix, rears are either a tattler or in some cases a modifier.

I have personally been involved in cat replacement (with high flow), removal and/or gutted many cats on domestic and foreign cars and trucks, and in every case we've tricked the sensor by using a spark plug fouler to space out the rear o2s. When they first started using the rear o2s, we didn't trick the sensor and the mileage suffered very noticeably. I know people with new Chargers and Nissans that have gutted their cats and experienced poor mileage afterward in the last couple months until either tuning them out or tricking them.

o1ls1ssmaro

......a rear o2 sensor....when detects a cat failure....IT WILL **** WITH THE PCM.....both 02 sensors front and rear have a chemical reaction happen in them when the exaust gas comes in contact with the end.......that reaction produces voltage.......the ammount of voltage sent back to the pcm will determine what ammount of fuel is to be delivered. the pcm is programmed to deliver the fuel based on the voltage reading of the o2 sensors.....sims will send a constant "perfect" voltage back to the pcm and then a precise tune can be done...........

when someone says that all it does is throw a light.... to me..thats like saying that the sensor that throws your low oil light is ok to get rid of...it just throws a light.......sure it just throws a light....but it throws a light because your oil is low........ your o2 sensor throws a light...sure its just a light....but it throws an ses light because the voltage that was read before the entrance of the cat, and what is should be when it left the cat is off... it senses that something is wrong with the emissions...your pcm will try to adjust the fuel delivery accordingly...... it will wind up guessing how much to deliver because it is not getting a definate reading upon exit of the the cat........
if i am wrong i will be amazed, but any respectable man can admit when he is wrong........if you have some way of better backing your arguement up... i would like to see it.....just so i can stand corrected...but untill i see some very very convincing data or tech article... i still think i am correct.......but you never know this may be something that i can come to learn that i was wrong about for a long time and can learn from this.....

killerwhale

bringing this back form the dead guys... i just wanna make sure im not buying rear 02 sims for nothing, i have no cats just full exhaust Lt headers and of course i have my original front 02 hooked up and i dont plan on getting it tuned anytime soon so i was thinking of getting the rear 02 simulators from ftp. so should i get them ?