Deleting the catalytic converters.... - DodgeIntrepid.Net Forums - Dodge Intrepid, Concorde, 300m and Eagle Vision chat
 
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post #1 of 14 (permalink) Old 08-11-2012, 06:43 PM Thread Starter
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Deleting the catalytic converters....

There are no emission tests and inspections in my local area, and annual safety inspections are a breeze; since they are not required to fail the vehicle if the catalytic converter is not present. So any legal concerns are not concerns.

Reason why I'm considering this is I've helped friends delete the catalytic converters on a few Dodges recently, from base line models to SRT models. The results are pretty overwhelming considering what cost and effort is put into the project ( results were spinning tires continuously from stop to gear three after the converter is deleted.). In the words of a few boy's at a local performance shop, it's free horse power!

I'm considering removing the pipes from the exit of the manifold to the first resonator, and just hallowing out the converters "innards" as they are and cleaning everything up nice and neatly. Then there is the option of having custom ones done up to exact spec in stainless steel (straight pipe so to speak). Either way I go here, I'll be required to purchase some valve bodies for the O2 sensors to simulate the air constriction that the converter is designed to do.

My concern is the PCM will not be able to compensate the A/F ratio's; that said, we have more then a few members running 4L stroker's off these PCM's no issue? This was an issue on a baseline Neon, tripped a lean bank one every few minutes, but ran incredibly for what it was. But those PCM's were designed for nothing much more then the 2.0L anyways.

Can anyone elaborate on the thought? I'd rather have the opinion of a few LH veterans before I start paddling down river!

All I'm looking for is a fun project and maybe gain a few horses and some torque for kicks, not compete with the nitro dragsters. :P

Last edited by TrepLovin; 08-11-2012 at 06:47 PM.
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post #2 of 14 (permalink) Old 08-11-2012, 07:28 PM
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the 02's in front of the converters are the a/f ratio sensors. the second ones are for catalytic effeciency. knocking out the cats won't change your a/f control, as long as the 02 sensoes are left.
it will trigger an engine light most times though, but as not living in an emissions controlled area, like me, it won't hurt. gains will be minimal, but possibly noticeable.
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post #3 of 14 (permalink) Old 08-11-2012, 11:36 PM Thread Starter
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Right on, thanks for bringing that to my attention. I forgot about the A/F sensors being in the manifold on LH's versus one in the converter and one after like the cars I've worked on recently.

Curious part is if it'll trip the code or not and if there is a way to "cheat" it. Perhaps a circuit that sends a constant voltage that the PCM indicates as "good". Oddly, once we constricted the air flow with that valve (you're given three different diameters, for the Turbo the smallest is desirable), it never tripped a code on either car for emissions; as said just lean bank one on at 2L beater Neon.

I gotta say the gains are very noticeable, I would have originally never thought it would do anything more then what a good exhaust system would; but it's a very night and day change. Curious to see it on the slant blocks as I'm talking from just inline block results. With two converters stripped it should be a nice added pep!
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post #4 of 14 (permalink) Old 08-11-2012, 11:40 PM
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Right on, thanks for bringing that to my attention. I forgot about the A/F sensors being in the manifold on LH's versus one in the converter and one after like the cars I've worked on recently.

Curious part is if it'll trip the code or not and if there is a way to "cheat" it. Perhaps a circuit that sends a constant voltage that the PCM indicates as "good". Oddly, once we constricted the air flow with that valve (you're given three different diameters, for the Turbo the smallest is desirable), it never tripped a code on either car for emissions; as said just lean bank one on at 2L beater Neon.

I gotta say the gains are very noticeable, I would have originally never thought it would do anything more then what a good exhaust system would; but it's a very night and day change. Curious to see it on the slant blocks as I'm talking from just inline block results. With two converters stripped it should be a nice added pep!
man it really inst worth all that work just to delete the cat
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post #5 of 14 (permalink) Old 08-12-2012, 12:03 AM Thread Starter
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Not a lot of work at all buddy! =D

I need to remove the pipes anyways to repair a patch during the 3.5 swap (remove 2" piping). Knocking out the webbing inside is a good frustration release. The pep is worth it of it is anything like it was for my buddy's cars! The CEL is just a few wiring tricks worst case.

Messing with a car beats the wild crap people do now and days!
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post #6 of 14 (permalink) Old 08-12-2012, 12:17 AM
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there are cheaters you can find for the second 02's. results are variable. i've heard of using anti-foulers to get the 02 out of the direct exhaust stream works as well. none of these are from personal experience. just stories i've read.
i did know 1 person who did use the cheaters, they did work for a while apparently.

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man it really inst worth all that work just to delete the cat
i've removed many. cutting out when plugged, and cutting at the opening and smashing the insides out. depends on where in the exhaust it is and how hard replacing/welding in a replacement pipe is.

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post #7 of 14 (permalink) Old 08-12-2012, 02:27 AM
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Not a lot of work at all buddy! =D

I need to remove the pipes anyways to repair a patch during the 3.5 swap (remove 2" piping). Knocking out the webbing inside is a good frustration release. The pep is worth it of it is anything like it was for my buddy's cars! The CEL is just a few wiring tricks worst case.

Messing with a car beats the wild crap people do now and days!
ahh i wouldnt do it but if you have some work to do around that area might as well
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post #8 of 14 (permalink) Old 08-12-2012, 04:06 PM
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Not a lot of work at all buddy! =D

.....The CEL is just a few wiring tricks worst case.....
I've given this a bit of thought before too considering many people want to delete the exhaust treatment on the newer diesels. But my main thought is that I highly doubt that the O2 sensors give a constant voltage. My bet is that the voltage varies depending on operating conditions and that the ECM probably looks for the changes in each sensor to correlate with each other.

Not saying that I am right, but if it is in fact a constant voltage throughout all operating conditions, then it would be as simple as figuring out what voltage and current it runs at and finding the appropriate resistor to wire in place of the sensor.
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post #9 of 14 (permalink) Old 08-12-2012, 04:34 PM
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just stick in a couple of O2 sensor "cheeters"
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post #10 of 14 (permalink) Old 08-12-2012, 05:19 PM Thread Starter
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I've given this a bit of thought before too considering many people want to delete the exhaust treatment on the newer diesels. But my main thought is that I highly doubt that the O2 sensors give a constant voltage. My bet is that the voltage varies depending on operating conditions and that the ECM probably looks for the changes in each sensor to correlate with each other.

Not saying that I am right, but if it is in fact a constant voltage throughout all operating conditions, then it would be as simple as figuring out what voltage and current it runs at and finding the appropriate resistor to wire in place of the sensor.
Turns out it's not a constant voltage, it's a pattern.

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just stick in a couple of O2 sensor "cheeters"
That's the usual way to go actually. But it's a hit or miss it seems. People say they work, half the time. Could just be user error though in most or all cases.

The spark plug fouler way is a popular alternative, which is more or less the vibrant airflow restriction adapters I've used on turbo vehicles.
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post #11 of 14 (permalink) Old 08-12-2012, 09:31 PM
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My understanding is that the O2 sensors put out a sawtooth and that the fr4equency of the sawtooth is a measure of the capacity of the cats. IOW, if the cats are shot, the frequency is high as the fuel system is continually overcorrecting first in one direction, then the other. If the cats have good capacity, then the effects of the changes in the fuel system at the output of the cats are buffered, so the changes in O2 sensor readings is slower (lower frequency).

The non-foulers move the downstream sensors out of the direct flow, so the changes that it senses are less rapid.


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post #12 of 14 (permalink) Old 08-12-2012, 09:44 PM
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My understanding is that the O2 sensors put out a sawtooth in response to the fuel system constantly correcting between lean and rich, and that the amount of change of the O2 sensor is a measure of the capacity of the cats in absorbing the changes. IOW - if the cats are dead, the changes in the exhaust will be seen almost unchanged by the cats, so downstream O2 output will go thru much wider excursions. When cats are working, the cats "filter" the large pre-cat excursions so the downstream O2 sensor output is less extreme.

The non-foulers move the downstream sensors out of the direct flow, so the changes that they sense are less than they would be if measured directly in the flow.


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post #13 of 14 (permalink) Old 08-13-2012, 02:33 PM
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See, problem with this is that you would have a larger diameter chamber right out of the manifolds. Thats a restriction. Unless your cats are plugging(meaning you have other engine issues), you won't see any difference except in sound. If your cats are still fine, I wouldn't do it.

But if you are, why smash them out? You could easily take and scrap the cats, buy the exhaust tube, and weld it in place. All you would need is to cut the flange off the front of the cat and re-use. Best part is you may come out with extra money.

BTW, the anti-foulers work great for me. Never had a check engine light from that. And they are cheap.
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post #14 of 14 (permalink) Old 08-13-2012, 02:59 PM Thread Starter
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See, problem with this is that you would have a larger diameter chamber right out of the manifolds. Thats a restriction. Unless your cats are plugging(meaning you have other engine issues), you won't see any difference except in sound. If your cats are still fine, I wouldn't do it.

But if you are, why smash them out? You could easily take and scrap the cats, buy the exhaust tube, and weld it in place. All you would need is to cut the flange off the front of the cat and re-use. Best part is you may come out with extra money.

BTW, the anti-foulers work great for me. Never had a check engine light from that. And they are cheap.
Yeah I've given that a lot of thought. My best bet is to just delete them and not "hallow" them out. I know the going rate is $50 a pop for each converter around here (local yard guy told me).

Those spark plug anti-foulers are the exact thing we've been using by vibrant on a lot of vehicles, just the vibrant kit has different diameter holes to switch between. Didn't know "anti-foulers" were the name of them!

Last edited by TrepLovin; 08-13-2012 at 03:03 PM.
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