I was just wandering if i removed the two back cats would it mess anything up ??

Thanks
ole_smokey_88

 

oh by the way its a 2002 f-150 5.4 ltr motor

 

Not again.....!!! Do a search youll see.

 

It is a sensitive subject around here along with anything to do with gas mileage. That shouldn't be reason why you can't ask though.....just remember; opinions are like a**holes...we all have one.

"If" you want my opinion, there are no real gains to be made if that is what you are implying, and you will have a bright "check engine light" staring at you while you drive.

 

well there is four of them and all im really wantin to do is make my flowmaster bark a lil louder i was just gonna maybe take the back two off but there is no o2 sensors around them or nothing i mean i'll still have my front two those are the ones that really matter aint it ? im new to the whole emissions stuff i got a 88 and a 89 with no cats

 

Actually it is the opposite. The front are pre-cats or heaters and the rears are the ones that matter. Some around here and other sites gut the fronts and keep the rears claiming better sound, performance and such...I personally don't like to muck with them because they are pretty free-flowing enough.

If you are looking for more sound the cheaper alternative would be to cut the flowmaster out and weld in a piece of straight pipe in its place. I did and it sounds pretty good and loud.

 

Cool thanks for the help man i really appreciate it

Ole_smokey_88

 

I disagree. At least in my case. All 4 of mine are gutted. After 1500+ miles, no CEL. It did come on about 200 miles after I originally gutted them, but AdvanceAuto is on my way to/from work so I had them reset it once.


Wrong. All 4 are 'real' cats. No such thing as "pre-cats" on these trucks.



"ole_smokey": If you have the extra time to kill, and nothing to lose...then go ahead. You will lose a small ammount of low-end torque, it will smell like an old hot-rod, and there is a chance the CEL will continue to come on. But you will get A LOT more sound out of it.
If I had to do it all over again, I would have left mine alone purely for the fact that I'm trying to sell it. If I were to keep it for the rest of my life, then I would be fine with it. I had the entire exhaust out of my truck when I was replacing the manifold gaskets...so I said "F-it" and went for it...



If you do plan to gut them, this is where you will need to cut and re-weld the pipe on both sides:









....and here comes Club Wagon....

 

Do yourself a favor and don't "get them"....
you're doing nothing for performance. just making it sound like a badly tuned chainsaw. Do the right thing and replace them with 2 or 4 high flow cats or at very least weld in some straight pipes rather then gutting the cats and leaving big expansion chambers to mess up your exhaust velocity.

I went with the idea of welding in 2 high flow cats in place of the 4 when my front 2 cats had become destroyed. I just cut them all out and put 2 new ones in in place of the back 2. Sound is great, no CEL, power and fuel economy are still there.

 

Really?? I was under the impression the fronts were just there as heaters to burn off fuel from a cold engine start, and the rears were purely for emissions.

Regardless, I don't see any benifets from removing or gutting them if you plan on keeping the truck for some time.

Any luck selling your truck yet ATC?

 

You guys were on this like flies on stink, looks like there's little need for me to argue against removing cats yet again. You beat me to it!

xtrford: "there are no real gains to be made if that is what you are implying, and you will have a bright "check engine light" staring at you while you drive"

"Regardless, I don't see any benifets from removing or gutting them if you plan on keeping the truck for some time."


I still recall when I used to get attacked for posting the valid reasons not to remove cats. Nice to see converts placing the dubious pursuit of sound into perspective & enthusiastically carrying water for performance, emissions, value & perhaps even the Federal Clean Air law that set penalties for removing cats.

 

I agree with club wagon, also there are noise issues. I don't know why every harley guy takes the mufflers off their bike and every kid cuts a perfectly good exhaust system off a vehicle for no reason other than to make noise. There should be enforcment of noise regulation. I strongly suggest you leave the cats and mufflers of your truck. Give your community some piece and quiet. OK, I am off my soapbox.

 

Mines on and off. It will stay on for a week or two, and then go off, and its been off for a good month now. Dont bother me none though....

Really...??? A badly tuned chainsaw. ( I couldnt keep my mouth shut on this one). I guess my truck must really sound like **** huh? And I am pulling 15-16 mpg city.

 

When i had my 97 I pulled the cats off of it. There is a huge increase in sound if thats what you are looking for. (it does make a guy wonder when it does get louder, is that really restricting some exhaust flow?)

I noticed slight improvements with performance and mileage but it wasnt anything huge.

I never have the check engine light come on either.

 

if you want more sound just cut off the 10 foot long tailpipe after your muffler and do a simple turndown, that pipe has a million restrictive bends in it anways. get a lot more sound out of your truck, less weight, and you're still emissions legal (well maybe not noise emissions)

and if you're real into hillbilly style....do the straight pipe instead of the muffler. but that would be loud as sh#t!