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Discussion Starter · #1 ·
I want to know:
what size the factory pipes are
what size the hole is on the stock exhaust manifold's outlet

I plan on buying new ball/socket connectors and running high flow cats, into a dual in dual out magnaflow with straight pipes out to the back. I had my cats tested and my drivers side cat has died, rather than replacing the y pipe of 3 cats and keeping the incredibly restrictive exhaust I'm going an easier route I plan on keeping all of my o2s I'm just going to put the rear two behind the magnaflow... that will keep the cel off right?

It would also help to know what sizes I should be working with. 2.25in or 2.50in... and which length muffler I should purchase

Thanks all.
 

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from what i understood you said nothing about replacing cats right? If so yes they will set off a CEL. You can just place two high flow cats and the CEl would be fine. If you go offroad you will need MIL eliminators-60$ or a tune to turn the CEL off.
 

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So as I'm understanding you'll replace the cats on both sides but wire in a single 02 sensor behind the muffler and distribute that sensors output to both rear 02 sensor connections? If so, it could work but you'd have to try. One thing you might run into is that the PCM monitors the voltage input and output of each sensor as well as the grounds so I don't know how you'd get around it detecting a circuit malfunction in one or the other.

For a 4.6L the highest I would go is 2.5". IIRC, the stock piping is 2.25" before the Y and 2.5" after the Y. I don't know about the manifold outlet though.
 

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I think its 2" before the "Y", 2.5 when its single, and 2" when its back to double again. And I'd love to know about the manifold connection myself.
 

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Discussion Starter · #5 · (Edited)
basically I'm saying the o2's would be where they are now just with a mid mount muffler in place of the third cat, and high flow cats in place of the stock upper cats. This will throw no codes right?
 

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Discussion Starter · #6 ·
also I really would like to know the outlet of that exhaust manifold so I'm not chopping up the old system, I want to start off new.
 

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1995 Thunderbird LX 4.6 red
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the exhaust manifold is large enough for a 2 1/2 pipe. im pretty sure that the stock pipe from the manifold is 2". Youve seen my stockpile of parts. thats exactly the setup im gonna run. Im gonna use 2 1/4 pipe all the eay front to back.
 

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the manifold out lets are 2" but they have a colar a lil before the outlets. The collector is 1/8" so that diameter is 1.75". Also the driver sides outlet is pinched due to the turn it makes. It has a C shape and from side to side the pinced side is 1.5". I belive the downpipes are 2" and take a nasty turn into the cats.
 

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Discussion Starter · #10 ·
which is why a much higher flowing setup must occur
 
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