Cats for 2007 Mustang GT

[Laurence Dunn]

Hi all, I have a smog test soon and my Long Tube Header and X pipe dual exhaust requires 2 new cats. What are my legal options please? All the cats I've seen so far say for off road use only.

 

[rocknrod]

You can get a 48 state approved H pipe, just like oem - https://www.amazon.com/05-10-Mustang-Engine-Catalytic-Converters/dp/B071D6R73H?gQT=2
or

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[StockishS197]

Hi all, I have a smog test soon and my Long Tube Header and X pipe dual exhaust requires 2 new cats. What are my legal options please? All the cats I've seen so far say for off road use only.

Depends on your state/county emissions testing requirements along with what LTs you have.

I have Pypes LTs and their metallic spun cats (300 cell) and mine passes OBD2 emissions testing. If you have sniffer testing, you can look for a higher cell cat to have welded in.

 

[Autokyrios]

Assuming you're county lets you have relocated cats (which you do with the LTs) then you want a "green" mid-pipe if you don't already have one. Knowing your LT maker would help, but most have offerings you can check out (Kooks, Pypes, Hooker, BBK, etc).

Most places will say "off road use only" because they don't want to get involved if you get a fail. Some dumb**** out there decided that cats don't work if they're not in the factory position and made that a fail criteria. So even though you may chemically pass, you've moved them so they magically don't count anymore.

If you don't have that restriction, do you know what you have will fail (assuming you have cats)? If there's no mid-pipe available from your LT manufacturer, you can get cats and have them welded in.

 

[Laurence Dunn]

Depends on your state/county emissions testing requirements along with what LTs you have.

I have Pypes LTs and their metallic spun cats (300 cell) and mine passes OBD2 emissions testing. If you have sniffer testing, you can look for a higher cell cat to have welded in.

I'm pretty sure my whole system is a Pypes LT and Bombs set up, our emissions are Euro 4 post 2006 car, so the same as your 48 state EPA probably. Not quite CARB. CO: 1.0g/km THC: 0.10g/km NOx: 0.08g/km. Maybe I need these https://www.pypesexhaust.com/produc...onverters-ceramic-substrate-cvm10k?sku=CVM10K

 

[Juice]

You dont want to hear this, but putting the stock stuff (headers & cats) is the only sure way to pass smog. Im sure the LTs are not road legal.
That said, if the smog tester overlooks the non-OEM parts, you still need the obd monitors to be on & complete. If you are tuned for cat delete, guess what...
On to aftermarket "off road" cats.
1 must comply with your car, CA or non CA cats. And 2, some am cats throw cat efficiency codes and CEL.

 

[Dino Dino Bambino]

Hi all, I have a smog test soon and my Long Tube Header and X pipe dual exhaust requires 2 new cats. What are my legal options please? All the cats I've seen so far say for off road use only.

You're in the UK and AFAIK, the only requirement is functioning cats regardless of location. That said, you'll want them as close to the engine as possible to ensure they warm up quickly and prevent ECU fault codes for cat efficiency.
Therefore I suggest you opt for a pair of Pypes 2.5" cats and position them immediately behind the header collectors. They're 300 cpi and will have no problem passing emissions, whereas cats that are 200 cpi or less will almost certainly fail. The cheaper ceramic cats are fine for a N/A application but for forced induction, you'll want cats with a metallic substrate.

 

[Laurence Dunn]

It passed the Pennsylvania smog test in 2021 after previous owner put some cats on instead his cat delete pipes. I may just need to go back to stock and do it all properly.

 

[Autokyrios]

Sorry, missed you were in UK.

 

[Laurence Dunn]

You're in the UK and AFAIK, the only requirement is functioning cats regardless of location. That said, you'll want them as close to the engine as possible to ensure they warm up quickly and prevent ECU fault codes for cat efficiency.
Therefore I suggest you opt for a pair of Pypes 2.5" cats and position them immediately behind the header collectors. They're 300 cpi and will have no problem passing emissions, whereas cats that are 200 cpi or less will almost certainly fail. The cheaper ceramic cats are fine for a N/A application but for forced induction, you'll want cats with a metallic substrate.

This is very helpful info, thank god for forums and the people who help each other!