how many cats?

[Maverick]

back pressure does absolutely nothing for a 4 stroke engine. don't spread poor info, please do some research before you post.

Yes they do need back pressure. Take your manifolds off and run your engine for a while and see what happens. Most 4 cycle engines benefit from some back pressure, it's been dyno proven. You need to do more research before you jump all over somebody for "spreading poor info".

To the OP. Since your truck came with two cats, "legally" that's what it suppose to have on it, no matter what. If you have lax smog laws (or none like in some places) yes your truck will be fine with only one cat on it.

 

[JohnnyO]

I didnt know we could run one cat.

Whatever passes the emissions test is usually fine. Some states have more stringent visual inspections than others, so removing one and leaving one would still not pass. Where I live (as far as I know, I am not an inspection mechanic) they don't care what you modify as long it passes the test. If I showed up with a 460 and 6-71 blower sticking through the hood and it passed the test, it's all good. Later model trucks, like my last two Sport Tracs, have two smaller pre-cats below the manifolds and a larger cat in front of the muffler. The precats light off quicker because they are small, so that the engine passes emissions when cold. After the large cat warms up then the pre-cats aren't really needed. I know people on the Sport Trac board who have replaced the pre-cats with a Y-pipe, left the single large cat, and it still passes emissions.

 

[Lifted2x]

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

The reason you only have one is because it is OBD1 (pre 96) OBD2 (96 and later) use two O2 sensors a upstream and down stream. One will be before the cat to monitor air/fuel ratio then one after the cat to monitor cat efficiency. (that it is doing its job).

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.

No you are wrong as the post above me says a gasoline engine will perform better with a broader power curve with some exhaust restriction. So you need to check where your misinformation is coming from. The only engines that would benefit from near zero restriction is extreme performance and diesel.

 

[kunar]

i stand by my statement and will continue to do so unless someone can prove me wrong with real info. "restriction" in an engine is a bad thing. with that said, i have no reason to add anything else to this thread unless someone can bring some valid info rather than hearsay to the conversation.

 

[Lifted2x]

i stand by my statement and will continue to do so unless someone can prove me wrong with real info. "restriction" in an engine is a bad thing. with that said, i have no reason to add anything else to this thread unless someone can bring some valid info rather than hearsay to the conversation.

All this coming from the guy asking if 2" exhaust is enough for a 4.0? Plus other members saying the same thing...

Your above statement that "restriction in an engine is a bad thing" is all you have to prove what you say?

 

[MountainMike]

I converted my truck over to one cat last weekend.

 

[Sasquatch_Ryda]

Dude....there's a foot in a shoe under your truck...

 

[shane96ranger]

I converted my truck over to one cat last weekend.

No station would say a word about this in Utah if you passed. Nice looking set up.

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.

This is true, you need a 3 way converter for all 3 processes to occur. This is perfectly legal here.

 

[Bondo]

Whatever passes the emissions test is usually fine. Some states have more stringent visual inspections than others, so removing one and leaving one would still not pass. Where I live (as far as I know, I am not an inspection mechanic) they don't care what you modify as long it passes the test. If I showed up with a 460 and 6-71 blower sticking through the hood and it passed the test, it's all good. Later model trucks, like my last two Sport Tracs, have two smaller pre-cats below the manifolds and a larger cat in front of the muffler. The precats light off quicker because they are small, so that the engine passes emissions when cold. After the large cat warms up then the pre-cats aren't really needed. I know people on the Sport Trac board who have replaced the pre-cats with a Y-pipe, left the single large cat, and it still passes emissions.

Thanks for the reply JO.

I wasnt meaning just run one of the original 2 cats, but get an after market one to replace my old stock ones in the near future. I didnt know the original 2 cats had 2 different "jobs", and that 1 after market cat would do both at the same time. Maine isnt doing emissions testing for inspections, so as long as theres something under there that is a cat Id say Im all set legal-wise.

 

[Surrey]

Yeah. Even up here in British Columbia, where we have quite strict emissions standards, as long as there is physically a cat present, and it passes the test, your good to go.

 

[koda6966]

My question goes along the same lines so I'll post here.

My exhaust rusted apart, it's been rewelded but the weld broke again since it's in an awkward place. The break is right after the 2nd cat.

Would I be able to just cut out both cats, and put in one of those fansysmansy magnaflow 49 state cats?

What I would be doing is this. (Sorry for the poor paint skills. Scanners down so I can't sketch it up)

 

[Sasquatch_Ryda]

Yes you could do that without issues.

What will happen? You will have a well functioning catalytic converter and no more exhaust leaks. Win win.

 

[MountainMike]

Dude....there's a foot in a shoe under your truck...

Yeah, sometimes I find weird things in the box.

No station would say a word about this in Utah if you passed. Nice looking set up.

Thanks man. I know this truck must have had new cats put on it not to long ago because there was barely any soot on the elements. You could see light through both of them and the flange bolts were grade 8 hardware. Still feels like it's breathing a little easier though.

 

[koda6966]

Alright, cool.

 

[HRTKD]

bogusdill, what did you end up doing about your catalytic converters? I have the same engine/year so I'm curious how it turned out for you. I'm hoping that in the past 1.5 years you got it done. Almost all of my exhaust needs to be replaced so I've been scouring the forum for 4.0L exhaust posts.