Finally, Deleted rear cats!
Member
Joined: Apr 2007
Posts: 89
Likes: 0
From: Rocky Mount, N.C.
I agree with what you say. Why do these trucks have 4 cats anyway? Is 4 smaller ones supposed to be better than 2 large, or is it for redundancy should one start to fail? Like you said, it seems high flow cats would do about the same as two normal ones if not less. Any other trucks out there have a similar setup?
Thank you!
Well to what I know, and correct me if I am wrong anybody, the front cats ( pre-cats as they are identified as ) filter the exhaust and calm it down while doing so, and the rear converters do alot of sound resonating, and help cool the exhaust down much more so its not too hard. 2005.5+ trucks have two cats which are the pre-cats & rears combined into 1 big piece, so generally it operates just as any other one does, Ford just did it this way for some reason. I have never seen another cat system like ours, but since my rear cats wern't O2 monitored, I'm happy I had the 4 system 
.
I agree with what you say. Why do these trucks have 4 cats anyway? Is 4 smaller ones supposed to be better than 2 large, or is it for redundancy should one start to fail? Like you said, it seems high flow cats would do about the same as two normal ones if not less. Any other trucks out there have a similar setup?
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Last edited by DarrenWS6; Aug 30, 2008 at 06:55 PM.
Senior Member
Joined: Sep 2007
Posts: 490
Likes: 0
From: IL
yeah thats the O2s, but you can still do it. check out the last couple pages of the other thread about pre-cats vs. high flows or somethin like that. I was wondering the same thing and joshmac helped me out a lot with some pictures and a link. Pretty much, you can cut them out, replace it with exhaust pipe, and wire in an MIL eliminator which will keep you from throwing a CEL since it makes the computer think that cats are still there.
I didnt need to do this cause i didnt throw a code but.....The second O2s sensors job is to look for a difference from the first O2. I bought two sets of those large spark plug anti foul spacers. Drilled out the center of one and screwed it into another that i left alone. This is the same thread size and pitch as your sensor. You screw the spacer into the bung of the rear O2 and screw your sensor into the spacer. This will move the O2 sensor out of the exhaust stream and should make the O2 think the cats are there. Didnt need to do it but bought the stuff just in case....It costs about 7 dollars so i figured I would have the stuff JIK....If anyone wants to try it I will send you the set....
Member
Joined: Nov 2004
Posts: 16
Likes: 0
From: Camden, SC
Thank you!
Well to what I know, and correct me if I am wrong anybody, the front cats ( pre-cats as they are identified as ) filter the exhaust and calm it down while doing so, and the rear converters do alot of sound resonating, and help cool the exhaust down much more so its not too hard. 2005.5+ trucks have two cats which are the pre-cats & rears combined into 1 big piece, so generally it operates just as any other one does, Ford just did it this way for some reason. I have never seen another cat system like ours, but since my rear cats wern't O2 monitored, I'm happy I had the 4 system.
Well to what I know, and correct me if I am wrong anybody, the front cats ( pre-cats as they are identified as ) filter the exhaust and calm it down while doing so, and the rear converters do alot of sound resonating, and help cool the exhaust down much more so its not too hard. 2005.5+ trucks have two cats which are the pre-cats & rears combined into 1 big piece, so generally it operates just as any other one does, Ford just did it this way for some reason. I have never seen another cat system like ours, but since my rear cats wern't O2 monitored, I'm happy I had the 4 system
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Senior Member
Joined: Jul 2007
Posts: 630
Likes: 0
From: Gainesville/Orlando, FL
If you only cut out the rears you wont throw a CEL. I cut mine out last month and love it. I took them in to salvage and got $190 bucks for the pair. Spent 80 of that on Crown Royal, told my wife they gave me 50, and bought my girlfriend some flowers with the rest.
I didnt need to do this cause i didnt throw a code but.....The second O2s sensors job is to look for a difference from the first O2. I bought two sets of those large spark plug anti foul spacers. Drilled out the center of one and screwed it into another that i left alone. This is the same thread size and pitch as your sensor. You screw the spacer into the bung of the rear O2 and screw your sensor into the spacer. This will move the O2 sensor out of the exhaust stream and should make the O2 think the cats are there. Didnt need to do it but bought the stuff just in case....It costs about 7 dollars so i figured I would have the stuff JIK....If anyone wants to try it I will send you the set....
I didnt need to do this cause i didnt throw a code but.....The second O2s sensors job is to look for a difference from the first O2. I bought two sets of those large spark plug anti foul spacers. Drilled out the center of one and screwed it into another that i left alone. This is the same thread size and pitch as your sensor. You screw the spacer into the bung of the rear O2 and screw your sensor into the spacer. This will move the O2 sensor out of the exhaust stream and should make the O2 think the cats are there. Didnt need to do it but bought the stuff just in case....It costs about 7 dollars so i figured I would have the stuff JIK....If anyone wants to try it I will send you the set....
i'll probably just do it first without the MIL eliminators and if a code comes up, then do it. JoshMac didn't throw a code at first either, but i think he said after about 500 miles a CEL popped up.
I mean, theres no CEL & it isn't hurting anyone exept the sensitive ears lol, but if someone notices my rear cats not being there with pre-cats, hmm.. dont know what would be said.. hoping I would be able to leave with no b/s.
Senior Member
Joined: Apr 2008
Posts: 1,654
Likes: 0
From: Northern Alberta
Thank you!
Well to what I know, and correct me if I am wrong anybody, the front cats ( pre-cats as they are identified as ) filter the exhaust and calm it down while doing so, and the rear converters do alot of sound resonating, and help cool the exhaust down much more so its not too hard. 2005.5+ trucks have two cats which are the pre-cats & rears combined into 1 big piece, so generally it operates just as any other one does, Ford just did it this way for some reason. I have never seen another cat system like ours, but since my rear cats wern't O2 monitored, I'm happy I had the 4 system.
Well to what I know, and correct me if I am wrong anybody, the front cats ( pre-cats as they are identified as ) filter the exhaust and calm it down while doing so, and the rear converters do alot of sound resonating, and help cool the exhaust down much more so its not too hard. 2005.5+ trucks have two cats which are the pre-cats & rears combined into 1 big piece, so generally it operates just as any other one does, Ford just did it this way for some reason. I have never seen another cat system like ours, but since my rear cats wern't O2 monitored, I'm happy I had the 4 system
.
Senior Member
Joined: Oct 2006
Posts: 971
Likes: 0
From: Fayetteville, NC
Man, your truck sounds just like my 04 in the first video. That slight knocking noise. Like a mini diesel or something. Drove me crazy until I heard other F150 like that.
Exhaust sounds great. Let me see if I am understanding your setup correctly. You have stock manifolds > stock front cat > dual pipe > x-pipe > 2 maggies, then to tips?
Exhaust sounds great. Let me see if I am understanding your setup correctly. You have stock manifolds > stock front cat > dual pipe > x-pipe > 2 maggies, then to tips?
Man, your truck sounds just like my 04 in the first video. That slight knocking noise. Like a mini diesel or something. Drove me crazy until I heard other F150 like that.
Exhaust sounds great. Let me see if I am understanding your setup correctly. You have stock manifolds > stock front cat > dual pipe > x-pipe > 2 maggies, then to tips?
Exhaust sounds great. Let me see if I am understanding your setup correctly. You have stock manifolds > stock front cat > dual pipe > x-pipe > 2 maggies, then to tips?
Heres my exhaust specs.
https://www.f150online.com/forums/3394201-post2.html