2 Cats for smog, good/bad? S14 pre-cat/downpipe with s13 Cat

[S13-KA24DET]

I got an S14 and my smog is coming up
since the pre-cat/downpipe is the s14's cat followed up by a 'dummy cat' i was thinking what if i replaced it with an actual catylic converter, therefore having 2 catylic converters, but i'm not too sure cause the hotter a cat gets the better it works? maybe having 2 cats won't heat the 2nd one up enough? i don't know so i'm asking.

good/bad idea? just wanna know if it's good or not, i don't mind flaming as long as you at least provide me with some helpful information/understanding towards my topic, thanks

[dan240]

I wouldn't worry about adding another cat as long as the one cat you have is still in good shape.

If you do decide to replace the cat make sure you get a three way cat and not a two way since your in socal.

I spent $150 on a two way on my Jeep before I realized what I had done. 1 year later I had to pass smog and had to replace it with a $200 three way.

Best,

[gotta240]

haha. great question. I've always wondered the same thing.

[Bay_Area_sr20det]

just as a reminder cats burn unburnt fuel. and they need to be at a sertan temp. so the closer you get them to the down pipe the better. i saw a pic of someone that made a custom down pipe with a cat almost at the bend. then another one fallowing whare the stock one was. it worked for him. and he said he ran his car real hard before smoging it.

[slideways2004]

make sure the cat is real hot b4 going in. it works great when its hot. we used one of those stethescope things to find this out. I'm not sure if this was the prefered method but we caused a vacuum leak and that casued teh enigne to run hot while running it to like 2-4k rpm. we watched the nox and everything go down on the graphs

[phreze]

While s14 and s13 are different. I just pased the Illinois emisions test with my sr20. I went in the first time expecting to fail, seeing how I had zero cats and sometimes smell unburnt fuel.

Ended up passing real easy like. Dont have the sheet in front of me but the numbers where half of the max acceptable.

[Indolent]

hmm, i'm wondering the same thing
now we all know that yes a cat works best when it's as hot as it can get

but it doesn't seem like the question has been answered yet..
so far it seems like 2 cat's would be great IMO, while one gets hot at least the 2nd cat.. even though not as hot would still work in some way correct?

but would having two cats be safe, thinking about the 'back pressure' thing, someone enlighten us haha

[Cashizslick]

I have been wondering the same thing . . multiple cats on a turbo 240 . .


Let us know how it turns out.

[dan240]

I can only add that my WRX has a cat inside the downpipe and also in the mid pipe. (it did stock anyway)

Dan

[redsuns3838]

just run 1 cat, why waste the $?

like stated earlier, usually places just start it up cold and u dont pass and try to sell u a bunch of shit thats not broken.
insist on keeping it warm before they test it, and just keep it hot until it gets tested.

[Indolent]

just run 1 cat, why waste the $?

like stated earlier, usually places just start it up cold and u dont pass and try to sell u a bunch of shit thats not broken.
insist on keeping it warm before they test it, and just keep it hot until it gets tested.

i barely got my s14 and need to get smogged in a month, it hasn't been all that well taken care off, so i don't think it would pass with flying colors
I got an s13 cat laying around, if it's going to help i don't see why i shouldn't try, rather than risk not passing and wasting more money, hell i might just want to save the hassle and get illegal smog

[EchoOfSilence]

you know you can just fail it once and retest for no extra charge right?

just get a good cat, check ecu for codes, fix accordingly

[ManoNegra]

Cat is there for emissions purposes, to clean your exhaust gases and bring the levels of HC, CO2 and NOx to acceptable levels as deemed by your state.
OBDII S14s have 2 cats as do all 96 and above car models, never heard of a cat in the downpipe.

Having a warm cat doesn't do a thing for your results. Having a warm engine does.

If you're running pig rich and your cat is burning the excess gas (HC) you'll eventually melt the honeycomb and plug it.

One properly functioning cat is all you need.

Didn't know there where places where one could do emissions with a 2-way cat.

[EchoOfSilence]

I'll disagree there. the catalyst material has an operating temperature that needs to be met before it does what it's supposed to. That's why new cars are coming out with cats that are electronically warmed up at startup to cut that downtime out

[ryan hagen]

Having a warm cat doesn't do a thing for your results. Having a warm engine does.




your right and wrong, warm engine is good because your in closed loop. but the cat needs to be at its operateing temp. thats why toyota puts theirs right on the cast iron exhaust manifold. nissan did it with the sentras. the cat must be hot to be at its maxx efficienecy, thats why on cars/trucks with longer downpipes to the cat are useing double wall pipe, is insulates and keeps the exahust temp up to light the cat off faster.

[Indolent]

OBDII S14s have 2 cats as do all 96 and above car models, never heard of a cat in the downpipe.

on s14's the honeycomb is on the downpipe, also called a 'pre-cat' or whatever, then if you look at the 'cat' on an s14 you'll see it's empty, this is called the 'dummy-cat'
http://pic13.picturetrail.com/VOL465/2194199/9239712/192445826.jpg
http://pic13.picturetrail.com/VOL465/2194199/9239712/192445832.jpg
now i'm wondering about the effects of replacing the dummy cat on my s14 in exchange with my s13 cat laying around how it'll effect my smog readings or if it'll blow up my engine or anything like that, i already know that it needs to be warm to get the best results yada yada yada lol

[projectRDM]

Won't harm anything, we did it on a local car that got an S14 KA swapped in since that's all we had at the time, it was a SOHC and I always throw out OE exhaust manifolds. With both cats it's dead ass quiet but there's a noticeable drop in power. It passed smog fine.