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How many cats do I need to lose until i'm deemed a hooligan?


Danpow
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After this years MOT it has become apparent that my center section has more holes than a hookers tights! So it seems to me i have two options:-

A) Weld the !Removed! out of the stock pipe.

B) Get a new pipe.

Option B is the favored at the moment but if i will be doing so i'd like to go de-cat. On saying that i also would like to be able to pass the MOT emissions test without having to replace a pipe every year. 

From what i can see there are two cats, One in the center section and one in the up pipe. So the question i have is, can i get away with a de-cat center pipe on an MOT?

I have read through some articles and found mixed answers so decided to post myself. 

I have a 2003 WRX, for reference.

Thanks!

DSCN2664.JPG

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Your car has 3 cats, one in the up-pipe, one in the downpipe and then another between the down pipe and centre section (cat pipe).

You will still be able to pass emissions with just the downpipe cat as it is the largest, the other two help pass emissions when cold.

I have replaced all of my cats and gone with a prodrive sports cat downpipe. Not quite as good as full decat but still pass emissions!

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2 minutes ago, Sandals said:

Your car has 3 cats, one in the up-pipe, one in the downpipe and then another between the down pipe and centre section (cat pipe).

You will still be able to pass emissions with just the downpipe cat as it is the largest, the other two help pass emissions when cold.

I have replaced all of my cats and gone with a prodrive sports cat downpipe. Not quite as good as full decat but still pass emissions!

I thought I may have been wrong! haha, So there's no cat in the center section anyway? Sorry i sound like a complete tool, I haven't much of a clue when it comes to this!

Good to know i can still pass the MOT with a few cats removed though! I guess i'll just have to make sure the cars nice and warm before it gets checked over! haha

Thanks!

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Yeh, your exhaust has several bits after the turbo:

Downpipe (cat)

Cat-pipe (cat)

Centre pipe (Resonator, no cat)

Back box

With just the standard downpipe you should pass with no issues (like you say, make sure they give it a blast before testing) but the downpipe is probably the most restrictive part unfortunately due to the cat and the bell mouth being narrow... wastegate side is just a plate essentially

 

torsive_downpipe.jpg

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2 minutes ago, Danpow said:

Ah right! I can see now, I'm even mistaking the uppipe and downpipe! haha. 

Thanks man, that's cleared that up! 

 

No problem mate! The up-pipe is def worth doing... albeit, a complete ball ache to replace. Not to worry you but if the cat in the up-pipe fails... bye bye turbo!

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3 minutes ago, Sandals said:

No problem mate! The up-pipe is def worth doing... albeit, a complete ball ache to replace. Not to worry you but if the cat in the up-pipe fails... bye bye turbo!

Fair one! i'll look into that then haha, I quite like my turbo without the insides of a cat run through it! 

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2 minutes ago, Tidgy said:

Just man up, full decat and just find a friendly MOT garage.

 

Will need mapping if you do sack all the cats off.

Eventually i'd love to! but for now the funds are the issue! haha

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Im in the same boat.. How important is the new map without any cats?

Ive removed my last cat and have no engine managment light come on,

 

I want to remove the other two

whats the one i should leave in if i cannot get the map done as of yet.?

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44 minutes ago, Tidgy said:

will throw up a CEL if you do that rear cat

If you get a replacement cat pipe with a hole for the o2 sensor you won't get a CEL... that's what I did as it was the first cat in my car to go

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25 minutes ago, DannyM said:

Im in the same boat.. How important is the new map without any cats?

Ive removed my last cat and have no engine managment light come on,

 

I want to remove the other two

whats the one i should leave in if i cannot get the map done as of yet.?

The downpipe cat must get mapped if you remove it... other cats aren't as important but you won't see the benefits without a map.

You will only get a CEL if you start removing the o2 sensors or the temperature sensor in the up-pipe. The temp sensor can be removed and you can put a resistor in the plug to remove the CEL

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