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Old 09-18-2007, 04:30 PM   #1
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Default High Flow Cats.........or hollow out the stock ones??

i am trying to decide what do do. are all magnaflow cats high flow?? i need part number 94056. or should i just hollow out the stack ones?? i also talked to a guy that would bend me a test pipe and inatall it for $40. i can turn off the rear o2 sensors with my predator. what do you all suggest? after this is a going to install headers.
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Old 09-18-2007, 09:22 PM   #2
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well I have a 1993 and I hollowed out my cat and have no exhaust right now. I like it, its pretty loud and raspy, but I'm going to be installing a dual exhaust soon and I'm just going to keep my hollowed out cat on there, its already there and I it doesn't cost extra. I also don't have to worry about emissions so thats another reason I did it.
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Old 09-18-2007, 09:31 PM   #3
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Don't know anything about the magnitude of the benefits provided by high flow cats. I suggest that this path would be preferable to either of your other options listed, both of which are illegal.

However, not sure what the vehicle inspection or enforcement activity is like in your area.

Of the remaining two options, the test pipe gives you higher exposure than hollowing out since it would be picked up by a simple visual inspection. It may also present problems when you sell - may have to put things back right as a condition of sale. Muffler shops can get in serious trouble for installing test pipes for reasons other than testing.

Also, laws change. Should your area adopt mandatory emission testing, you'd have to put things back right anyway.
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Old 09-19-2007, 12:33 PM   #4
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wde3477 is correct in what he is saying

Unfortunately from a performance stand point hollowed out cats or hi-flow cats really DO NOT do anything for you unless you are running a boosted application or higher hp application (typically over 400 whp)

A hi-flow cat specifically is a shorter length larger diameter inlet and outlet cat which will give you more of a raspy sound but thats really about it. The best way to gain hp and torque through a modified exhaust is through a quality set of headers and a properly designed cat back system.
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Old 09-19-2007, 05:56 PM   #5
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For best results remove the cats. Run a 2.5 or 3 inch pipe with quality mufflers. Not Flowmasters. Use Magnaflows or Borla.
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Old 09-20-2007, 12:40 AM   #6
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well here is my thoughts right now. i know a guy that has an SRT10 truck and has no cats, full 3 inch exhaust. nothing has ever been said to him. there is not emissions check or testing in my area right now. they are bringing in some kind of new fuel that burns cleaner. my thoughts were to clamp in a piece of pipe in their place and not hollow out my factory cats. that way if something does come up i can have them welded back on or simply install high flow cats. any thoughts??
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Old 09-20-2007, 05:05 PM   #7
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I would suggest new high flow cats instead of hollowed out cats. I have read on several forums that hollowed out cats can cause turbulence in your exhaust creating a loss in peak horsepower.
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Old 09-20-2007, 10:44 PM   #8
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i think i am just going to cut out my cats and weld in a piece of pipe and save the stack cats incase i need to put them back in.
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