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Discussion Starter · #1 ·
Guys,
I'm thinking of deleting the cat on my 04.5 to improve power, egt's and fuel mileage, but I can't find hardly any info on the net about it. I'd like to know if I can just go out and buy a 4' peice of pipe and clamp it in myself without issues and what kind of results I can hope for. Any info available out there? :confused013:
 

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hydraulic lifter crew
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yeah you wanna ride in my truck and see if
you like it. ill be in brownwood next weekend.

you can take it to a muff shot and they can
weld a pipe in or you can buy the mbrp cat
delete pipe which fits like a freakin glove..
 

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Discussion Starter · #3 ·
My truck's all stock right now with the only modification being holes drilled in the bottom of the stock airbox. I've got around 80k miles on it so far. Ya think getting rid of the cat will help power and mileage?
 

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hydraulic lifter crew
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it may make egt's run a bit cooler. i felt no
improvement on the butt dyno though.

your mpg's will surely go down due to your
right foot being heavier than before trying
to make that cummins purrrrrrrrrr :thumbsup:
 

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cat removal

I would suggest just cutting a small part after the cat and unclamping it. Then gutting the cat and putting it back in place. Since without it you void any kind of after market warranty
 

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:ditto: :ditto:
 

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Tech Specialist
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no power increase/decrease, no mileage increase/decrease, EGT's down by 50F MAX.

the only plus side to CAT removal is the exhaust smells like what a diesel should and not a propane grill.
 

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I noticed 1 MPG gain, and a seat of the pants difference, I have no EGT gauge so I dunno about that.

Install was a !#$% sucker, it fit like a glove, but I hate slip fit exhaust pipes. PERIOD!
 

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I might put mine back on. I liked the sound better and I lost low end when I took it off. I did gain some top end but that's not what I bought it for. I know everyone is going to call bs but I have documented proof that my egts went up while towing after the cat came off. A boost fooler took care of it but it was a dramatic rise. I'm open to theories on that.
 

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aww take it off... i just unclamped it and you'll have to work a lil to get it off, then measured it, went to the muffler shop and bought a piece of pipe a 1/2 to 1 inch shorter so i had a lil room, then went to the semi shop and bought two of the band clamps they use to hold the flex pipe on with and put the pipe on with band clamp and waa laa... if you need to take it back in for warranty use the band clamps and put the cat back on... had mine in a couple times doin it and they never said anything... you could spray paint the clamps brown so they dont stand out but the dealership won't say anything if the cats on there. but if you take the cat off tap one end on the ground and you'll see how much crap they catch... i had a neat little pile of soot when i tapped mine on the concrete. :) lol
 

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Didn't notice any difference in power/mpgs.. but EGT's certainly run cooler, especially when towing.

I also think that they will soot up when you don't tow, which can degrade performance until they get HOT.. And I also smoke less now that its gone, guessing because before I was blowing all the soot out of it.
 

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Discussion Starter · #13 ·
Thanks for the advice fellas.

I think I'm going to take the truck to the local muffler shop and get them to gut the cat and install a freer flowing muffler. I crawled under the truck to do the gutting myself today, but the clamp had crimped the pipe pretty deep making me afraid that if I was able to get it apart I probably wouldn't be able to put it back together.
 

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no power increase/decrease, no mileage increase/decrease, EGT's down by 50F MAX.

the only plus side to CAT removal is the exhaust smells like what a diesel should and not a propane grill.
LOL. That's exactly what it smells like. :hehe:
 

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see in my situation, i took the cat off (unbolted the clamps and took it out (and it was a $%*@! sucker to get out)) that way if i have to go to the stealership, i can put it back on... I took the cat off ran the truck for a week and then took the muffler off. I personally didnt feel much difference in the seat-o-pants meter, i didnt have guages yet so IDK about egts but i seen mileages go up about 2-3 mpg.. running 65 down the highway... taking the muffler off i felt a lose in midrange power.. and it was obnoxiously loud.. i put the stock muffler back on til i find a more free flowing muffler
 
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