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Cat position on a Y

This is a discussion on Cat position on a Y within the External Engine forums, part of the LSx Technical Help Section category; I hope this is not a daft question but in looking around at different brands of headers i have noticed ...

  1. #1
    Member speedyWS6's Avatar
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    Cat position on a Y

    I hope this is not a daft question but in looking around at different brands of headers
    i have noticed that some brands of catted y pipe have both cats mating to the headers
    directly whilst the TSP Y for example has the cats differently placed.
    One cat is mating to the header directly and one is further down nearer the merge of the Y?

    Any reason for this or is it really no big deal where they are placed? I cannot imagine there
    is a real issue. The forward O2's are not going to be influenced, and the rears will be deleted so.....

    I know header questions have been asked to the nth degree but cannot find any mention
    of this point anywhere? Just curious really.

    Thanks....

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    Spaz is My Mentor SMWS6TA's Avatar
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    Placement of the CATS effects the performance of the CAT. Further away from the engine = less effectiveness, because the CAT's use heat to perform in their task. The design of the headers effects the location of the CAT's. This is why some states do not allow CAT back systems.

    Now the reason why SLP vs other manufactures place theirs is most likely for clearance. SLP CAT Y pipes have know issues with clearance. Most ppl just get a non-CAT Y pipe (known as a ORY =Off Road Y-pipe) and delete the CATs entirely. Some states you can get away with it while others no. I see you're in the UK so I'm not sure how your countries laws will effect you.

    I've honestly never seen a CAT LT headers before, only on the Y pipe. Not saying it's not possible, just saying I've never seen one that's all.

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    I know the obx system is right off the headers kooks are as well.
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    Member speedyWS6's Avatar
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    Scott,

    Apologies...

    You mis-understand! I know full well headers do not have cats on them!!!!

    If you look at this TSP catted Y Texas Speed 3" Catted Y-pipe
    then you will see the cats are differently placed
    than this Kooks link. 1998-2002 Chevrolet Camaro And Pontiac Firebird LS1 3" x 2 3/4" Catted Y Pipe 5.7L

    Please, have a look.

    Jeff has pretty much go it, in that the cats ( when welded to the Y) are closest to the header collector with Kooks
    whereas the TSP is simply different and i wondered if it will make a difference in
    any way?

    I may be in the UK, Scott,but i don't listen to many people here as they have no clue at all!! This is why i am on here!

    OH.... one more thing. My last WS6 had full SLP front to back ( on it when i bought it!!) with spun hi flow cats which
    i installed to replace the rattly SLP cats and it passed our emissions fine, but NO cats would be a problem i expect!

    Trev
    Last edited by speedyWS6; 04-22-2014 at 01:06 PM.

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    Probably no real difference as long as you go with a high flow style cat.

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    Senior Member Too Fast's Avatar
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    Quote Originally Posted by speedyWS6 View Post
    Scott,

    Apologies...

    You mis-understand! I know full well headers do not have cats on them!!!!

    If you look at this TSP catted Y Texas Speed 3" Catted Y-pipe
    then you will see the cats are differently placed
    than this Kooks link. 1998-2002 Chevrolet Camaro And Pontiac Firebird LS1 3" x 2 3/4" Catted Y Pipe 5.7L

    Please, have a look.

    Jeff has pretty much go it, in that the cats ( when welded to the Y) are closest to the header collector with Kooks
    whereas the TSP is simply different and i wondered if it will make a difference in
    any way?

    I may be in the UK, Scott,but i don't listen to many people here as they have no clue at all!! This is why i am on here!

    OH.... one more thing. My last WS6 had full SLP front to back ( on it when i bought it!!) with spun hi flow cats which
    i installed to replace the rattly SLP cats and it passed our emissions fine, but NO cats would be a problem i expect!

    Trev
    The closer to the engine a converter is, the more efficient it is since there is less heat loss. Now with that said, the Texas Speed Y set-up would be marginally less effective cleaning the exhaust then the Kooks.

    Some new engine designs offer no way to install headers, since the exhaust port on the head is a single outlet, with the converter almost directly on the cylinder head. I believe the new GM 3.6 is like that, and the Chrysler 3.6 may be like that.

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    Moderator Firebirdjones's Avatar
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    I believe Scott hinted at the reason you see the cats moved in different places depending on manufacture. For clearance reasons. Depending on how a particular manufacture bends and routes their Y-pipes may dictate where they have to put the cats to clear certain things under the car while still providing ground clearance.

    Even a 3" Y-pipe without cats is a snug fit under there, and the driver side is always prone to banging the floor when the engine moves if you get it too close. So a larger bulge in that area (cats) would have to be carefully placed, and likely moved further down stream if it provides more room.

    Either way it's not much of a concern in my eyes, since you are deleting the rear 02's. At least the cats are still installed and doing something, and would likely please the tech officials during inspection so long as you don't have laws about moving them further down stream. Some places here like California for instance, won't allow the cats to be moved from their original OE configuration (so no long tube headers)

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    Quote Originally Posted by Firebirdjones View Post
    I believe Scott hinted at the reason you see the cats moved in different places depending on manufacture. For clearance reasons. Depending on how a particular manufacture bends and routes their Y-pipes may dictate where they have to put the cats to clear certain things under the car while still providing ground clearance.

    Even a 3" Y-pipe without cats is a snug fit under there, and the driver side is always prone to banging the floor when the engine moves if you get it too close. So a larger bulge in that area (cats) would have to be carefully placed, and likely moved further down stream if it provides more room.

    Either way it's not much of a concern in my eyes, since you are deleting the rear 02's. At least the cats are still installed and doing something, and would likely please the tech officials during inspection so long as you don't have laws about moving them further down stream. Some places here like California for instance, won't allow the cats to be moved from their original OE configuration (so no long tube headers)
    Yes...that's the point I was trying to make.....

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    Member speedyWS6's Avatar
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    Guys,

    Thanks for all the input and i understand what you are saying.

    I figure if the Kooks Y has both cats at the collector end then this is
    an indication that this is a good bet.

    What i may do, ( but no hurry here) is to buy an ORY, buy a couple of the spun
    Magnaflow cats (P/N 59959) and once the car is in the air to do the work, offer
    up and align everything between headers, cats and Y and then remove and weld/fab
    as needed with the cats in the most suitable spot (for clearance) in the Y pipe.

    I know..... you may think "why not buy a catted Y"? Well the TSP ORY with 2 quality
    Magnaflow spun cats is less expensive than the TSP catted Y and i like fiddling and with
    this method i have the "luxury" of picking the best spot to suit the fitment.

    Cannot see this will be a bad plan..... unless somebody is happy to pour cold water
    on it for any reason?!!

    Trev
    Last edited by speedyWS6; 04-23-2014 at 10:56 AM.

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