Daft question re Cat bypass pipe

[Rob Evans]

Do I need any gaskets when swapping out the bypass pipe to put the CAT on (for an MOT) or is it just a simple unbolt one, bolt on the other?

Cheers,
Rob.

[Northnoble]

I just bought a Cat by-pass and it came with two gaskets....

[Mattv6]

I'm going to be fitting a new exhaust shortly. Are the gaskets reusable? Or will I need to buy new ones?

Thanks

[Northnoble]

If you are lucky...yes!

However, my engine / manifold gasket was a bit scored etc when it came off so decided it was best to replace.

[Mattv6]

Cheers ill order a couple.

[smokin]

The metal gaskets for the bypass/ cat are reusable but normally need a bit of a clean to remove soot deposits. Do you have your own cat? There's a club one that gets passed around if you need one

oh, and when you come to put the bypass back on the factory usually put a smear of sealant on the gaskets. I never do and have never had a leak once tightened properly,  which can be a challenge

[fieldl]

If your removing the manifold that does need a new gasket.  I've had the exhaust off including the cat bypass and they are fine for reuse.  I'd replace them if it was easy though.

[fieldl]

Why though is the cat bypass pipe of a smaller diameter than the manifold and exhaust 

[Monza]

are you sure of that ? manipulate several in 7 years and didn't notice this !
how many mm less in diameter ?

[fieldl]

You can just about see the difference only a few mm in the picture below even with the wrap:

[fieldl]

Maybe that's a Chinese component they would understand the difference

[Northnoble]

OMG......what is that!?

That could not be more different from a standard UK setup!

[fieldl]

It did look exactly the same until I mapped the car and found the exhaust silencer far too restrictive so it got removed and replaced with what I could get.

[speedmachine]

Thats an atom 2 setup , from the top of the cat bypass...it isn't anymore,,there it becomes a horn! How on earth do you manage to not get banned from the tracks? I guess it makes about a million db...

[fieldl]

There are noise regulations in China but they aren't exactly enforced.  It's not too loud but it wouldn't be acceptable in the UK.  What's the difference between an Atom 2 and 3 manifold/exhaust system then?