I have had a high flow cat on my 98 2.3 EX since last spring and am very sick of the horrible gas mileage it has caused without a bung for the secondary 02 sensor. I'd like to pick up a oem replacement soon but have a few questions. I'd prefer a high flow cat but it must have a bung in place.

What are some things to keep in mind when choosing a cat?
What affects will a 1.75 inch outlet have compared to a 2 inch outlet?
What is an "AIR tube"?
Any recommendations for under $150?

TIA for any help!

 

dude just go to any old muffler shop and ask them to weld in a bung for your o2 sensor.

no more than $20 later you'll be all done.

 

So the sensor only needs a hole in the pipe to function properly?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HandoEX &raquo;</TD></TR><TR><TD CLASS="quote">So the sensor only needs a hole in the pipe to function properly? </TD></TR></TABLE>

yes and no, the car will still not going to close loop operation if your cat isn't working right.

a good high flow car like random tech will pass smog and effectively cut down the smog but there's like 90% of the so called cat is just a mufflered pipe that have no effect on emission control.

if you put a bung and sensor to a test pipe, it will still throw code and give you sh_tty mileage.

BUT, there's couple of trick you can do to avoid the cel(not sure it will give you all the gas mileage back but i bet it will help).

you can use a..

mechanical defouler or electronic o2 simulator to fool the ecm.

more info upon request

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HandoEX &raquo;</TD></TR><TR><TD CLASS="quote">So the sensor only needs a hole in the pipe to function properly? </TD></TR></TABLE>
yes, as long as your high-flow cat is working properly that's all it needs - a bung after the cat.

if it still throws a code drill out the bottom of an 18mm spark plug defouler about 1/2", mount the o2 sensor in it, then screw that in after the cat. no CEL and the car will run like normal.

 

Thanks for the help guys
I bought an o2 sensor simulator but decided not to hook it up after hearing poor reviews.....I figured it wasn't worth relacing a sensor if the simulator failed quickly.

About the spark plug defouler....are there different styles or are they all the same? I bought a set of them tonight for a couple bucks and noticed that one end is threaded on the inside (larger hole) and the other end is threaded on the outside (smaller hole). So do I enlarge the hole on the end with the smaller hole and screw that end directly into the bung on the cat?

edit* I bought Help brand defoulers...part # 42009.

 

there are different sizes. you need the 18mm defouler. not sure what you have by part number but it says the size right on the package.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HandoEX &raquo;</TD></TR><TR><TD CLASS="quote">noticed that one end is threaded on the inside (larger hole) and the other end is threaded on the outside (smaller hole). So do I enlarge the hole on the end with the smaller hole and screw that end directly into the bung on the cat?</TD></TR></TABLE>
yes that is correct.

 

Great I'll hopefully get this set up soon

I'm still trying to figure out how in the world this works though?

 

it's simple. the 2nd O2 is merely checking to see if there are less emissions after the cat than before it. by moving the sensor out of the direct exhaust gas stream the sensor "sees" less emissions and thinks everything is A-OK.

 

OK, gotcha...thanks again

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by iam7head &raquo;</TD></TR><TR><TD CLASS="quote">yes and no, the car will still not going to close loop operation if your cat isn't working right.
</TD></TR></TABLE>
A 2ndary o2 sensor has no effect on closed loop operation or gas mileage.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by notoriousB &raquo;</TD></TR><TR><TD CLASS="quote">it's simple. the 2nd O2 is merely checking to see if there are less emissions after the cat than before it. by moving the sensor out of the direct exhaust gas stream the sensor "sees" less emissions and thinks everything is A-OK.</TD></TR></TABLE>
An o2 sensor doesn't see "emmisions". Like it's name says, it senses oxygen and nothing else.

 

^^ OK so explain how it knows the gasses are cleaner after the cat (meaning the cat iw working) than before it if it only senses oxygen.

I understand it's name, thanks smart ***, how about providing some details to educate us further.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by notoriousB &raquo;</TD></TR><TR><TD CLASS="quote">^^ OK so explain how it knows the gasses are cleaner after the cat (meaning the cat iw working) than before it if it only senses oxygen.
</TD></TR></TABLE>
The cat uses oxygen to in the process to reduce emmisions of HC an CO. So the ecu expects to see a lower oxygen level after the cat. (meaning it's doing it's job)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by notoriousB &raquo;</TD></TR><TR><TD CLASS="quote">

thanks smart ***, </TD></TR></TABLE>
No, thankyou.

 

just stop any ideas of jimmy rigging ur car ur lossing a lot of money and power from the missing o2 just fork the money out for a universal high flow cat with a o2 sensor bung already in it. problem solved emissions will be decent and gas mileage will be much better. i did the same thing got a high flow with no 02 sensor hole. and i suffered with shitty gas mileage. remember u get what u pay for so just do it right and no more worries.

 

the defouler trick is proven and works fine. I've done it on many cars already.

let's see, $4 pack of defoulers vs. $200 cat... hmm... yeah buy the cat.

 

The way I see it, I have nothing to lose by trying the defouler trick. If it works, I saved plenty of cash. If it doesn't work, I wasted a whopping $3.00