High flow Cats vs LTH?

[Jklapko10]

I’m having trouble balancing cost vs gains vs noise. I don’t want my car to be obnoxiously loud because one of the tracks I go to has noise restrictions and I already need turnouts to pass sound with an MBRP Race catback. I know the majority of gains from the exhaust come from the cats, so I’m wondering if anyone’s ever cut out the factory cats and put high flowing ones on the stock headers? Even if it means less gain than LTH with high flowing cats I’m not too concerned.

The engine (2017 GT PP) currently just has a CAI and catback, I have a Gen 3 manifold waiting to be installed with either headers or high flow cats, injectors and tune.

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[GregO]

headers or high flow cats,

Does your area have emission inspection/testing ?

 

[Jklapko10]

Does your area have emission inspection/testing ?

Unfortunately yes

 

[GregO]

Unfortunately yes

That could become a problem for you.
I recently learned Utah enacted full visual under hood and cat placement inspections backed up with pictures.

 

[Jklapko10]

That could become a problem for you.
I recently learned Utah enacted full visual under hood and cat placement inspections backed up with pictures.

I’m in Arizona, I know several people who have passed with LTH high flow cats

 

[Howitzer]

If you're talking 200 cell cats, you'll throw a CEL and if you use cheaters, you won't pass a visual inspection if they check for it where you are (if not, then you can use an O2 extension to most likely not throw the CEL).

High flow 400 cell cats would work but I don't think I'd bother spending the money on that without the headers unless you needed higher power/temp rated cats. I don't feel like any gains on that alone would be worth it.

You could always swap with catless test pipes constantly I suppose.

I have mbrp street, lth and high flow(400 cell, epa rated) cats for reference. I have full visual emissions inspections where I'm at. Your local laws may differ.

 

[HKusp]

On an N/A car the stock headers and cats flow enough to support well over 700+ horsepower at the wheels. There are forced induction cars running deep into the 9's with the stock headers and cats. You are going to go to a shit ton of trouble going with high flow cats or LTH's to get little to no gains. Especially if you are worried about noise too. I would spend that money elsewhere.

 

[engineermike]

Stock cats are 750 cpi I believe. The backpressure imposed by them is very low when na, likely less than 2 psi. I think I would worry more about the 2” sections of exhaust than the cats.

 

[AZlb5.0]

I think going catless is going to get old quickly. Now for performance you have to look at everything you’re doing and if adding headers is going to help in what you’re trying to achieve then by all means get them.

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