new here with ? about the catylitic converter

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KYHIGHRIDER
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new here with ? about the catylitic converter

Post by KYHIGHRIDER »

i made a stupid judgement call on my part and gutted out the cat cause i thought it would help out some performance. well since ive done it the truck seems to have lost some of its bottm end, its kinda sluggish on take off. is this due to the cat. i plan on putting a new one on and run some duals on it. thanx in advance.
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Post by F9K9 »

First off I want to welcome you here :wink: I am sure that we will both learn from HenryJ and Killian/Steve about our late rmodel converters and that they are pretty much free flowing. The precats have caused problems but I have not had any issues with my '02
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Post by HenryJ »

Did you run a muffler and tailpipe after gutting the cat?
I would not blame the lack of bottom end exclusively on the cat removal.

It is true that there needs to be some back pressure to provide the best performance. I do not know what the need is on this engine.
This back pressure can be attained from even a given length of open pipe. If you were running a muffler and had a tailpipe run behind the axle, I can not see back pressure being a problem.

Any chance debris from the gutted cat is plugging the muffler?
Did you clear the PCM after removal? It needs to relearn.
Are you throwing codes? If you are the engine may be compensating in ways that are detrimental to the performance.

I think you are on the right track replacing the main cat. There is really no gain running without. Lets us know if you get that low end back.

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Post by KYHIGHRIDER »

yeah im runnin aa aftermarket muffer which is free flowing muffler and a tailpipe that runs in factory location. the codes have been reset several times. its showing that the o2 sensor is bad. i figure that is part of the trouble. i had replace the intake gasket not to long ago and noticed the truck has been runnin rich.
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Post by drperry »

Which O2 sensor code are you getting?

If it's for the one after the cat, then that's not your problem...

If I remember right, that's P0137...
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Post by killian96ss »

The codes you are getting for the 02 sensor are probably for the post cat 02 which monitors exhaust gasses coming out of the cat (OBDII).

When you gutted the cat the emissions went up triggering the code.

There is little if any gain from removing the cat, not to mention your emissions will go way up, and it's a federal offense to remove any part of the emission system. :wink:

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Post by roadrunner »

killian96ss wrote:The codes you are getting for the 02 sensor are probably for the post cat 02 which monitors exhaust gasses coming out of the cat (OBDII).

When you gutted the cat the emissions went up triggering the code.

Steve
Just a little off topic but I've noticed quite a few parts sites say that all three O2 sensors are the same part number. Can't speak for OEM but if this is true why would the third one trigger a code without the cat functional? Or is the computer interpreting the data from that one differently? My understanding of linear O2 sensors is they simply "tip" back and forth at a preset air fuel ratio. Engine too lean=too many impulses on lean side telling pcm to richen mixture and vice versa for too rich condition. This differs from a digital sensor in that it will simply "read" the air fuel mixture and then it's up to the pcm or intermediary adapter to tell the fuel system what to do. So with digital an air fuel ratio can be varied over a wider range and won't go over rich on coast-down compared to a linear one. Comments? Additional knowledge or understanding?
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Post by killian96ss »

All 3 factory 02 sensors are the same part #, and read the same way in millivolts.

The post cat 02 is uses a different table or different parameters to determine whether or not the cat is efficiently burning the remaining exhaust gasses.

In other words the post cat 02 is looking for "leaner" #'s to verify proper cat operation, and if it detects an exhaust content as high as the pre cat 02's it will set the SES light.

The post cat 02 has nothing to do with how the engine runs, and is only there for OBDII monitoring purposes.

I'm sure someone else ( :idea: Brule) could explain this better, but that is a rough idea anyway of how it works. :wink:

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Post by HenryJ »

The "after cat sensor" looks for the difference in readings from the forward sensors. This difference is used to measure efficiency of the cat.

Is that simple? ;)

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Post by roadrunner »

Thanks guys. Makes perfect sense!
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Post by killian96ss »

HenryJ wrote:The "after cat sensor" looks for the difference in readings from the forward sensors. This difference is used to measure efficiency of the cat.

Is that simple? ;)
I knew you could explain it better than me just rambling on. :lol: :thumb:

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Post by roadrunner »

Hmmmm, gives me an idea. The rear sensor could be "fooled" with a resistor with a little investigative ingenuity if you really wanted to get rid of the cats.
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Post by killian96ss »

roadrunner wrote:Hmmmm, gives me an idea. The rear sensor could be "fooled" with a resistor with a little investigative ingenuity if you really wanted to get rid of the cats.
Casper Electronics used to make 02 simulators for years until the government stepped in and said " Not anymore :nono: " and called it illegal because it alters the emission system. :roll:

If you looked hard enough I bet you could still find some for sale.

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Post by roadrunner »

[/quote]Casper Electronics used to make 02 simulators for years until the government stepped in and said " Not anymore :nono: " and called it illegal because it alters the emission system. :roll:

If you looked hard enough I bet you could still find some for sale.

Steve[/quote]

Do you remember or know were they adjustable or fixed by model?
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Post by killian96ss »

They were not adjustable and I believe they were only specific to the type of 02 sensor used (same plug style).

All they did was prevent the SES light from turning on for people who ditched their cats.

They plugged into the harness where the 02's used to be.

I'm not sure how the electronics inside each one worked, but they were good at fooling the PCM, and some people were even passing emission tests with them on even though they didn't have cats. :?:

The EPA wasn't very happy once they caught on. :lol:

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Post by roadrunner »

The EPA wasn't very happy once they caught on.

I bet not!! Probably didn't bother the suits as much after they figured out how to get some big fine money rolling in because of it though.
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Post by killian96ss »

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Post by roadrunner »

Interesting. Thanks Steve. Always good to stimulate the gray matter juices.
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Post by HCO4x4 »

anyone found a way to cheat the code yet? i found a thing to wire into your system and it keeps the sensor from throwing the code. does anyone have a simulator they dont want?
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