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Discussion Starter #1
Hey Guys, (sorry if this is in the wrong forum, but I think it's okay here)

Let me start by saying the stock cat setup on the IS freakin sucks. It's bad enough you have to have 1, but 3, and in the worst possible spot.
Anyway I have an idea so Tell me if you think this would work. I've been tuning cars for a while now, but I've never had an idea like this or seen it done. I want to put headers and a race pipe on my car, but eventually I will have to get it inspected for emissions. So I can either do the mod and keep swapping my stock exhaust on and off every time I have to get it inspected or I was wondering if a single cat right after the race pipe would be good enough to pass. I know a single converter would be sufficient, because the 3 cat setup is just so it can be certified as a (LEV)
But I guess my question is this: will it totally kill all my power gain having a cat right there, and also would that be too far from the engine to work properly? I don't know if distance makes a diff. when cats are concerned. Sorry for the longwinded post, but if anyone has ideas, let me know. -Thanks-
 

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Get a hi-flow cat. Most shops won't even look for the other 2 as long as they see the one under the car.
 

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what i did in my honda was hollow out the cat. but i did not have to wory about emissions. any one asked it was the stock one. this does not help pass emissions unless you know "someone".
 

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it won't necessarily help you pass emissions because as you said, our cars are rated for LEV, which has a higher standard than before. in the case where you replace 3 cats with a single hi-flow, you probably will not get the emissions low enough to pass..
 

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in some places like here in Houston, the emissions check now plugs into the computer rather than doing a tailpipe test, so wouldn't disabling one or more of the cats send some signal to the computer letting it know something was wrong, or does it only check the first one? Nobody is crawling around the car here in TX, but it seems to me that it wouldn't be that hard to rig up some kind of a bypass around the cats.

You tap into the line upstream of the cats and install a valve that routes the flow through the cats or through a bypass that ties back in downstream of your cats. It is manually controlled and you lock it into position, so it doesn't accidentally change positions on you. When you take it in for an emissions check, you route the flow through the cats so everything is functioning normally, but for maximum performance, you run it through the bypass. With a little bit of fluid mechanics knowledge, it seems like you could create a system that was fairly efficient.
 

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Yeah an O2 sensor simulator would likely bypass this type of test the same way it keeps the CEL away...

XCstud said:
in some places like here in Houston, the emissions check now plugs into the computer rather than doing a tailpipe test, so wouldn't disabling one or more of the cats send some signal to the computer letting it know something was wrong, or does it only check the first one? Nobody is crawling around the car here in TX, but it seems to me that it wouldn't be that hard to rig up some kind of a bypass around the cats.

You tap into the line upstream of the cats and install a valve that routes the flow through the cats or through a bypass that ties back in downstream of your cats. It is manually controlled and you lock it into position, so it doesn't accidentally change positions on you. When you take it in for an emissions check, you route the flow through the cats so everything is functioning normally, but for maximum performance, you run it through the bypass. With a little bit of fluid mechanics knowledge, it seems like you could create a system that was fairly efficient.
 

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when you really think about it...it's not about the quantity (3 cats vs 1):

before we go on...for the guy who posted first...i don't mean to sound like an ass but you say you've been tuning for a while??? let me elaborate:

"It's bad enough you have to have 1, but 3, and in the worst possible spot. "

which "spot" are you talking about and why would you say it's in the worst possible spot??? just out of curiosity.

"I've been tuning cars for a while now, but I've never had an idea like this or seen it done. I want to put headers and a race pipe on my car, but eventually I will have to get it inspected for emissions. So I can either do the mod and keep swapping my stock exhaust on and off every time I have to get it inspected or I was wondering if a single cat right after the race pipe would be good enough to pass."

first of all, it's "header" not "headers"...our car only has one cylinder head. if you've been tuning for a while, i would think you would have seen high flow cats on cars. it's nothing new...guys have been doing this for quite some time now. also, it really depends on the type of cat you get. one really restrictive cat (like a damaged one) will not flow better than 3 high flow ones in series...that's just an example. so when all the guys say that taking out 3 and adding just one...make sure you add a good one that will flow better as well as work properly than just adding any old cat...

mustangs and camaros have been using high flow cats for racing and emissions control...try checking with your local speed shop that handles domestic cars too...they may have just what you're looking for...also, good muffler shops should be able to help you out as well...try checking with them as well...

good luck...
 

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Nygmatic
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youve never seen more than one cat on a car? try looking under a mustang LOL =) you'll find a variety there.

i believe there are setups where there are special "quick release" clamps for the cat that can be replace by regular pipe. this way normally you can run with the regular pipe, then when you need to pass emmisions, you can easliy swap the pipe for the cat. also run your car lean that day ;)
 

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florida has no emmisions, lol, but the other day my buddy shot out a 4-6inch flame out of his turbo volvo with 3' piping..and a cop saw it and stoped him, and ask if he had a cat, he said he just got a new muffler and the cop gave him a warning.... :lol:
 

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Okay, I said worst possible place because two of the damn things are integrated into the exaust manifolds, which makes it hard to pass a damn emissions test if you install aftermarket headers which have no cats don't ya think. And yes genius I have seen hi flow cats on cars before, just not in the spot I was talking about because it's closer to the rear of the car than the front. The single converter on most cars is usually installed after the exhaust manifold which doesn't make it very hard to swap out the exhaust manifold for a header and still pass an emissions test. And what's this sh_t about header vs. header(s)? who give a fu_k whether you add an (s) on the end or not? when I open the hood of my IS I see two exhaust manifolds that are not connected at the top where they bolt to the head. Maybe they meet at a tiny junction at the bottom to connect to the mid pipe, but who cares. And um, just out of curiosity, how many cylinder banks are we dealing with here? Oh that's right 2, they just both happen to be in line with each other as opposed to a V shaped engine with 1 bank on the left and 1 bank on the right. So if you have a "header" on each bank, wouldn't that be "headers" Damn I hate it when people nitpick at the f-in details and miss the point entirely
 

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About that header. If you look at the stock engine there are two of them. Each feeds into a cat and then they join into one and feed another cat. That's headers.

Also, I haven't looked under a Mustang since 1967 and I don't plan to.
 

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bartkat said:
About that header. If you look at the stock engine there are two of them. Each feeds into a cat and then they join into one and feed another cat. That's headers.

Also, I haven't looked under a Mustang since 1967 and I don't plan to.
good decision :lol:
 

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AbsolutLex said:
Okay, I said worst possible place because two of the damn things are integrated into the exaust manifolds, which makes it hard to pass a damn emissions test if you install aftermarket headers which have no cats don't ya think. And yes genius I have seen hi flow cats on cars before, just not in the spot I was talking about because it's closer to the rear of the car than the front. The single converter on most cars is usually installed after the exhaust manifold which doesn't make it very hard to swap out the exhaust manifold for a header and still pass an emissions test. And what's this sh_t about header vs. header(s)? who give a fu_k whether you add an (s) on the end or not? when I open the hood of my IS I see two exhaust manifolds that are not connected at the top where they bolt to the head. Maybe they meet at a tiny junction at the bottom to connect to the mid pipe, but who cares. And um, just out of curiosity, how many cylinder banks are we dealing with here? Oh that's right 2, they just both happen to be in line with each other as opposed to a V shaped engine with 1 bank on the left and 1 bank on the right. So if you have a "header" on each bank, wouldn't that be "headers" Damn I hate it when people nitpick at the f-in details and miss the point entirely
first of all, i got your point...that's why i answered your question...or didn't i???

as for your statement about the cat and not passing emmisions. thing is, you can install an aftermarket header and have a cat after it and pass emissions...it's basically that simple. just make sure your O2 sensors are going in to right locations and reading correctly as well. in your original statement you said you haven't or heard of something like this before...so i guess maybe i'm the one that's getting confused...

also, sometimes we nitpick cause guys come on here saying stuff like "i've been tuning for a while" or "i know my way around engines" so we just correct them...ever heard of constructive critism??? anyway, let's just say you go to a store...do you ask for an aftermarket exhaust manifold for your IS300 or do you ask for exhaust manifolds for your IS300??? or lemme ask this then...do you tell people you have AN IS300 or you have IS300s??? i think an "s" DOES make a difference...

listen, i was trying to be polite about it...but if you wanna start complaining, go right ahead...

one more thing, this discussion is in the FAQ and stickies up above...and we've discussed this many times over the past couple years...so let's not beat a dead horse...please...thanks

bartkat said:
About that header. If you look at the stock engine there are two of them. Each feeds into a cat and then they join into one and feed another cat. That's headers.

Also, I haven't looked under a Mustang since 1967 and I don't plan to.
once more...you're talking about the stock exhaust manifold...if you go out and buy an aftermarket manifold for the IS300, it's basically one piece...and it goes onto ONE cylinder head...so it's a HEADER...
 

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once more...you're talking about the stock exhaust manifold...if you go out and buy an aftermarket manifold for the IS300, it's basically one piece...and it goes onto ONE cylinder head...so it's a HEADER...

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It's still two pieces just hooked together.

Besides, what's up with this "tuning" thing? I was tuning up my cars back in the early 60's. Mostly that consisted of changing the plugs, points, and setting the timing.
 

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bartkat said:
once more...you're talking about the stock exhaust manifold...if you go out and buy an aftermarket manifold for the IS300, it's basically one piece...and it goes onto ONE cylinder head...so it's a HEADER...

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It's still two pieces just hooked together.

Besides, what's up with this "tuning" thing? I was tuning up my cars back in the early 60's. Mostly that consisted of changing the plugs, points, and setting the timing.
sending you a pm...
 
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