I installed a header. I have an o2 bung welded on behind my 2nd cat. I'm currently running the 2nd o2 sensor to open air. I assume that it reads it as being a very steady value comming out of the catalytic converter. It has not yet thrown a CEL, but it is running rich with a bit of a rich smell. When I actually get around to hooking up the o2 sensor, i assume it will lean out a bit.

My question, is there a difference between the front and rear catalytic converters? Will i get a error about the catalytic converter's efficiency, run just fine, or lean itself out?

The reason I'm asking is because

1. the distance from the heatsource (engine) has increased which gives alot of cooling before it reaches the cat, which means less burning of fuel from the first o2 sensor to the 2nd.

2. the piping is made of a much flimsier material then origonal stock cast, which will release heat too.

3. I believe the engine uses the difference in value from o2-1 sensor and o2-2 sensor to calculate a "clean emissions. If I use a less efficient catalytic converter, it may decide my emissions are dirty and lean my fuel out.



<span style="font-size:12pt;line-height:100%"><span style="color:#ff0000"><u>Turbo'd guys take note</u></span></span>- Right now, i'm wasting gas by having the 1st o2 sensor hooked up and 2nd o2 sensor to free air. I can smell the richness.

 

front and rear CATS? don't you have headers and a cat-back? you should only need one cat...

1st o2 sensor goes in the flex pipe
then comes the cat
2nd o2 sensor goes IN the cat at the end (post-cat)
then the rest of the cat-back

..

sorry i dont think i understand your question or your confusion.

 

^^ damnit, i know where the o2 sensors go. This is a question about how the computer interperates the data received by sensors.

Also, i have my 1st sensor at cyl 4

I assume that the reason they have 2 o2 sensors is to monitor the input/output and adjust the fuel ratio for emissions purposes. If that is the case, then I could be getting maximum power from my engine right now.

 

I am also a bit confused, but you second sensor is going to be the one that determines a lean or rich mixture because its after the cat, so by having it in free flowing air its bascially just reading oxygen right? making it rich. I'm suprised theres no CEL

 

^^ yeah, I was supprised as well. I assume it is doing this because there's no "flowing air" over the sensor. From what I've read, you can get more power from a bit of richness at the cost of gas efficiency. Lean will save gas, and not give you much power. I'm worried if the 2nd cat is less efficient then the 1st, it will lean me out because it sees more oxygen going through, causing a loss of power.

 

That sounds right, but im still a little confused, your talking about the two cats on the stock tib right? because you making it sound like you still have 2 on there. Yeah rich will give you more power as long as your not too rich. Most diags i've done we've found most power at about 11-12:1. Is it an after market sensor?

 

Actually, NA betas run SOO pig rich from the factory, that LEANER conditions will give you more HP.

Why are you still talking about 2 cats????????

The 2nd o2 sensor's ONLY function is to determine if a catalytic converter is installed/working properly. THATS IT.
The 1st o2 sensor is what controls your A/F ratio.

 

i've learned just the opposite as some cars only have 1 o2 sensor on them

 

<div class='quotetop'>QUOTE (DrivingTibNaked @ Feb 24 2007, 11:17 AM) <{POST_SNAPBACK}></div><div class='quotemain'>From what I've read, you can get more power from a bit of richness at the cost of gas efficiency. Lean will save gas, and not give you much power.</div>
where did u get that info, every engine building book ive read has said the most power a motor will make is on the brink of lean. the more fuel you add thats not needed will just rob HP.

and being that our cars run totally stock very rich, and can gain power by leaning out the fuel with no other mods says alot.

 

^^That's why 1.8 cams increase power on the 2.0 engine.

<div class='quotetop'>QUOTE </div><div class='quotemain'>^^ damnit, i know where the o2 sensors go. This is a question about how the computer interperates the data received by sensors.</div>
Then do it, and don't worry about it anymore. LOL.

<div class='quotetop'>QUOTE </div><div class='quotemain'>i've learned just the opposite as some cars only have 1 o2 sensor on them</div>
..??
Point is, the first o2 sensor STILL controls the A/F ratio.

If your 2nd o2 sensor fails, you get a CEL saying that your cat isn't functioning properly. Your A/F ratio remains intact (because the 1st sensor is still working).