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That Guy
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Discussion Starter #1
I was thinking about gutting out my catalytic converter and running a piece of pipe through it so that it still looked like I had one on there and would get better sound and maby a little more power. Someone told me that if I did that my check engine light would come on and the computer would run a different air/fuel mixture and would cause me to loose gas milage. Is this true? Also I know that doing this is not exactly legal but what cops dont know wont hurn them.
 

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I’m not sure if your truck has the pre and post O2 sensors or not. But in any case as long as you do not remove the sensors you should be fine. Fitting the converter with a tube is going to be hard work. It would be easier to install a high flow converter.
 

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That Guy
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Discussion Starter #3
It will be hard but worth it when its done. Thanks for hte help.
 

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I don't think that gutting the cat is going to make that much power, and your CEL will come on, because the Post cat O2 will read diffrent since the cat will not be doing it's job. If you want still do this, you will need a O2 simulator. What it does is plugs into the O2 sensor harness and tricks the computer by sending a signal that the computer wants to see. You can get them at www.summitracing.com I think they around $40 and they are made by Casper.
 

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minimoto is right, gutting a cat has very little gain vs. drawbacks. Especially on an n/a v6 it really won't make much difference aside from sheer sound and the smell of gas and along with that, the legality of it. I had a gutted cat on my supra before and after switching to a high flow 3" cat on that car the difference was very much noticeable and that was on a turbocharged inline 6 at 12.5 psi of boost. For one it was quieter and secondly it felt smoother in power delivery than the gutted cat. Now if you run a straight pipe through a gutted cat you won't have any of the associated air turbulence that affects flow, but you have to ask yourself, at what price. A good highflow cat will only show about 5 hp difference than a straight pipe...I dunno but I could live with -5 hp.
 

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Something interesting I learned today about removing the cats...

I asked my mechanic if he was going to put a CatBox (O2 sim) in to prevent any CEL's. He told me no, he's just going to coil the O2 sensor up and tie it to the frame where it can get fresh air!

I about fell over when he told me this. His reasoning is the sensor will show perfect catalyzation since its reading a high flow of clean air. He says he's done dozens of trucks this way, and exactly zero CEL's in all those years.

I couldn't believe it at the time, but since the exhaust went in this afternoon I've put about 100 miles on the truck. It keeps getting faster, and there's no CEL.

I have an R/T, so YMMV.
 

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That’s great that this is working but it may be short term. When the sensor gets wet or starts to build up with road dirt and oil it may short out.
 

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I saw that bridge on the map, and I'll cross it when I get to it. :D
 

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That Guy
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Discussion Starter #10
I did get my cat gutted and ran a straight pipe through it and it is awesome. I love the sound of no cat going into a flowmaster 40 series. My engine light did come on and now I am going to get that o2 simulator. I felt an acceptable amound of boost, not alot but there is a difference. As for the smell of gas I can smell some but its not alot. I am happy with the overall job and not its just a very nervous wait till inspection. I am going to a place that does not do emissions test and hopefully they wont catch it.
 

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Alta Boy said:
Hhhmmmmmm ...... Seems like a hack and slash method of doing something. Glad it's your truck and not mine. :cool:

You mean gutting the cat or my mechanic's little trick? There's nothing hack or slash about what he did. The sensor is coiled up and riding on top of a frame rail. If the CEL comes on I'll call KRC and get a Catbox from him. Its not going to affect the truck one way or another.

As far as gutting the cat... I wouldn't bother. Too much work when you can just weld in a piece of straight pipe. Or maybe buy an AR20 resonator and swap that in place of the cat. To the untrained eye it looks kind of like a cat.
 

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I don't understand this obsession with gutting cats. Most of them flow as well as performance mufflers unless they have deteriorated. If you put a tube inside of the cat, doesn't it reduce the inside diameter?

I would get a 3x3 high flow cat and get the performance you expect.
 

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Agreed, but I'm not obsessed with eliminating cats - in fact I prefer to have them. They perform a useful function, environmentally. The factory cat is worthless though - it reminds me of the pellet-type convertor I found under my 1981 Z/28 back in the day. Rather than keep that, I'd spend the $90 and get a Magnaflow or Powercat. They're 100cpi metallic substrate, and they flow almost as well as a straight pipe. They double as resonators and add a little tune to the sound.

I haven't had a cat-less car in the family since my Mom's 1970 Challenger 383, so I figured I'd try it out. So far so good. I may add Powercats in the future, especially if the CEL comes on.
 

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With today's technology in high-flow cats why would you run without one.Its not like your running 10-12 second 1/4 mile times,your driving a daily driver and polluting the atmosphere at the same time. HIGH FLOW CATALATIC CONVERTER $75 INSTALL $30 RUNNING AROUND TOWN WITHOUT ONE ON LIKE A JACKASS AND GETTING BUSTED PRICELESS!!!
 

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Besides having cats, a person can do more to help the environment by ensuring their vehicle is tuned properly. Catalytics are just icing on the cake, so to speak. And don't forget that a large proportion of the VOC's that are stripped by a cat are converted to sulfur traces that end up on the roadway. No such thing as a free lunch. Internal combustion is bad for the environment, period.

I still prefer to have them. I'll be installing cats after I get all the other parts on. Right now my AFR is so out of tune it would be a waste of money.

BTW: this truck will be in the high 11's by the time I'm done with it, but it will still have cats.
 

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That Guy
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Discussion Starter #17
Ok first off everybody has their own opinion and mine in to keep my cat off. Its only a little 3.9 and isnt hurting the air that much. Besides I live in a small ******* town where we all gut our cats and get our trucks as loud as possible. I did not gut it for the power but for the better sound. Now my little 3.9 sounds like a V8.
 

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So let me get this right .. The sensor is still plugged in ? and just sitting on the frame rail? :spam: I always new sensors needed to be in the air stream, measuring air or lack of oxygen in the exhaust. What happens when the vehicle is sitting still? with no air flow passing it. This goes totaly against everthing I come to know about driveabilty. This guy is a genius :bow: :bs2:
 

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00'4.7quad4x4 said:
So let me get this right .. The sensor is still plugged in ? and just sitting on the frame rail? :spam: I always new sensors needed to be in the air stream, measuring air or lack of oxygen in the exhaust. What happens when the vehicle is sitting still? with no air flow passing it. This goes totaly against everthing I come to know about driveabilty. This guy is a genius :bow: :bs2:
Its still plugged in, but its coiled up and wire-tied to the frame rail. I have no idea why it works, but it does. I have no problems at stops or any idle situation. The truck continues to run very cool, and the power is good. No CEL indications on the dash either. Until I can get a tune on the thing and have the post-cat sensor deleted in software, I think its a good short-term solution.
 
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