how many cats?

[bogusdill]

Hey there guys, one of my cats just crapped out and i got an idea i want to replace them with aftermarket cats but my question is do i need to get 2 cats because thats how many i have now or can i use just one?

also, the truck is a 91 4.0 4x4 with a custom cold air intake.

below is a pic of the cold air intake, its just a piece together thing from autozone

 

[88_Eddie]

just use one, go to an auto parts store and get one that will git onto your existing exhaust pipe.

a factory replacement is over $250 from a parts store, you can find a cat ment for a different vehicle and it'll work.

 

[bogusdill]

I was thinking about using this cat, what do you think? has anyone used this before? its the magnaflow 49 state cat. i already have hedman headers and have decided that im going to redo the whole exhaust system while im working on it.

 

[backroad101]

What about the o2 sensor after the cat?

 

[88_Eddie]

What about the o2 sensor after the cat?

that's true, i was thinking of my 88 when you said 2 cats. i only have 1 o2 sensor before the cats

 

[bogusdill]

i just looked under my truck i just have 1 O2 sensor before my cats, that thats interesting...

 

[88_Eddie]

i just looked under my truck i just have 1 O2 sensor before my cats, that thats interesting...

oh you have a 4 cylinder, i was thinking you had a 4.0

so you only have 1 bank on your engine, that's why you only have 1 before the cat.....there may be one after as well

 

[bogusdill]

no you were correct, i have a 4.0 however it does only have one 02 sensor which is located before the cats. im just curious if i can get away with using just 1 aftermarket cat instead of installing 2 like it is stock

 

[RollinWOT]

If your truck has 2, replace them both. If one goes out, it generally means that the other is soon to follow. Unless you want to build a whole new exhaust, in which case, 1 should do ya' just fine.

 

[bogusdill]

yes im doing a whole new exhaust, my muffler rotted out a few months ago so i just cut it off, i figure its time to replace that and the cats, i think im gona go with one cat and see how it works, my concern was maintaining enough back pressure. well see... thanks for all your input, very much appreciated

 

[kunar]

yes im doing a whole new exhaust, my muffler rotted out a few months ago so i just cut it off, i figure its time to replace that and the cats, i think im gona go with one cat and see how it works, my concern was maintaining enough back pressure. well see... thanks for all your input, very much appreciated

four stroke engines don't need back pressure. additionally, ford used 2 cats because they both contained different metals to perform different jobs. any universal cat will take the place of both of your current cats just fine.

 

[Diesel Ranger]

They don't cats either...............

 

[Strieg]

My stock setup is two, when I bought the truck the po replaced both and it cost hi
800$. But yeah I'd go for one new universal one, you should still have your back pressure, which IS IMPORTANT to power and mileage.

 

[kunar]

My stock setup is two, when I bought the truck the po replaced both and it cost hi
800$. But yeah I'd go for one new universal one, you should still have your back pressure, which IS IMPORTANT to power and mileage.

back pressure does absolutely nothing for a 4 stroke engine. don't spread poor info, please do some research before you post. the reason this myth stays alive is because exhaust that is too large will reduce the exhaust scavenging you'll find in a properly sized system.

They don't cats either...............

true

but.... thats not legal, which means we don't talk about that on trs.

 

[Bondo]

four stroke engines don't need back pressure. additionally, ford used 2 cats because they both contained different metals to perform different jobs. any universal cat will take the place of both of your current cats just fine.

I didnt know we could run one cat.

Nice to know for when I replace the exhaust system on my 87.