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Hello All,


I'm going to put a 4" exhaust system on my truck. It's a CA truck with all the smog crap
. Will removing the cat really make that much of a difference in EGT's or exhaust flow?


Thanks,


Chris
 

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I'm interested in this answer also. Same year - EC -SB

Bill
 

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I would have to say it will make a difference. Cats are very restrictive...more so than the muffler.
 

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Go for it!
My cat went astray and it made a considerable differance it responsiveness. Of coarse it didn't hurt that the replacement is the 4" Summit exhaust. I got rid of the cat restriction and the muffler restriction at the same time...You'll crap when you see how really small the holes inside the cat are...

Ox
 

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I dropped EGT's about 125 to 150 degrees removing the cat and replacing it with the 4in Banks pipe. Now I have a complete Banks System
 

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Can anyone say what the dealer will do when bringing the truck in for warranty service if it does not have a cat on it? Will they give me a hard time?
 

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Won't removing the cat set off the check engine light and screw with the computer? I know that on gassers there is a pre and a post cat O2 sensor. Wouldn't there also be that on the diesels. If so it would set off the check engine light because the post cat O2 sensor would be reading high emissions. And I would also be concerned that something else in the emission system would try and compensate for it, possibly hurting the motor. What do you think?
 

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Mr. Mister said:
Won't removing the cat set off the check engine light and screw with the computer?Ê I know that on gassers there is a pre and aÊpost catÊO2 sensor.Ê Wouldn't there also be that on the diesels.Ê If so it would set off the check engine light because the post cat O2 sensor would be reading high emissions.Ê And I would also be concerned that something else in the emission systemÊwould try and compensate for it, possibly hurting the motor.Ê What do you think?
No the cat is just basically there with no sensors, so the ECM doesn't know if it's there or not...the LLY may be different, but I doubt it. Basically the only thing that happens when you take the cat off is less restriction and lower EGTs...doesn't sound bad to me...
 

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Cool that's sweet for us. I ordered a LLY that should be here in February. Hopefully it won't have O2 sensors so I can be unrestricted!!
 

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Well I'd like to consider the removal of the CAT when my truck gets here, but I live in an area where emission tests are required to license your vehicle.


Part of that test is visually verifying that the equiptment is in place, so the removal is out of the question since the LLY can be determined to be installed by the VIN.


So while removing it might lower your EGT, it might also lower your bank account via a fine if you get caught. It is illegal to remove emissions equiptment.


Just something to think about.
 

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Diesels are exempt from Smog checks so far here in....., besides my '01 did not come with a CAT....should help re-sale don't ya think?
 

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I intend to just Gut the cat and leave it in place



Im not sure how I'll do it, but next week when I get my new exhaust system and take the old one off, I'll see how it looks and how I can 'Clear the channel'



I'll let you guys know my outcome in this thread next week...
 

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I bought my truck in Mass which requires the CA smog pack, but I live in RI where it is not. It's no big deal for me to remove it and add a complete 4" system. If I lived somewhere that required tests I would have got a system with the flange like the OEM. That way come test time, just switch out the down pipe and you're all set. I would NOT gut the cat unless I had another one for tests. While you can't see that a cat is gutted, the computer that tests you emissions would likely show higher nox

Ox
 

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years ago when cat first came out in cars we used to pop out a frost pulg in the cat drive around the block blow out all the junk and then put a new plug in all done
 

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My '04 did not come with a cat...if removing the cat screws with emissions then you might want to check with your dealer...on my Ford they said if you mess with emissions you void the factory warranty. I was also told that from the corp office of Hypertech. Who knows if that is correct or not I would still look into it. Just my thoughts...I am all for less restrictive intake and exhaust. Edited by: NoWake200
 

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What duramaxes came with cat? Mine is a 2003, and if there's a catalytic converter under there, I have sure missed it. Is this a CA thing or what?
 

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I of course would like to remove the CAT if possible since I'm familar with what they do to gas engines, but it's not as simple as it used to be. Especially with the new LLY since it's whole reason for being was to comply with the new EPA regulations for diesels taking effect on 01-01-2004.


First, it's a Federal requirement now for all 50 States, so where you live does not matter anymore.


Second, the warranty issue is something that you ought to explore as well. I'm reasonably certain GM will take the position Ford has, as NoWake200 has said.


It looks to me like the only real solution for the new LLY's is if the exhaust comes flanged so you could pull the CAT out except for tests. Of course you'd have to put it back in when you take the Edge out anytime it went to the dealer as well. I can see taking the Edge out, but changing a tailpipe before each trip could be a pain, especially if the truck happened to be disabled and you couldn't go home with it first.


It seems to me I saw something in another thread about a manufacturer who offers high performance low restriciton CAT's, anybody see that or know anything about it?
 

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Surprisingly in CA. we dont have testing on Diesels. I do like the idea of pulling it out intact and saving it just in case, but I dont think its flanged on both sides. I'll investigate.


So my only real concern would be if the dealer found out it was gutted. hmmm.
 

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dirty old man said:
What duramaxes came with cat? Mine is a 2003, and if there's a catalytic converter under there, I have sure missed it. Is this a CA thing or what?

I'm with you on the catalytic converters, someone must have stole mine? What applications have them, I sure didn't see one under my '04 LBY?
 

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Up until the first of this year, CAT's were on the LB7 engines sold in California, and I believe one previous poster said MA required CA emissions equipment.


Jan 1 of this year, Federal laws regarding diesel engine emissions were implemented that required GM to install the EGR and CAT on all Duramax's. That is the reason the LLY was introduced. I don't know what the other manufacturers had to do in order to meet this requirement, but suspect it's the primary reason behind the PSD 6.0 as well.
 
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