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Discussion Starter #1
Hi All and Happy New Year

156 v6

1st Question is the cf2 rear pipe that connects to the rear box the same size as the cf3. as i want to use the stainless pipe i have without the middle box and want to know if i need a reducer or not as im doing a exhaust order on other bits and want to include it if i need one.

2nd Question will i gain cleaner emissions from using my cf3 rear double cat then using the cf2 single cat (front cats removed) . Wondering as i dont want the car to fail mot on emissions. Also do any of the pre mot fuel additives work ?

Thx in advance
 

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I'm sure the bore size is the same for CF2 & CF3 2.5V6 (The Diesels also used the same bore).
3.2 was bigger.

Are you single turbo, or twin turbo (with one turbo per bank)?
 

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Discussion Starter #3 (Edited)
I'm sure the bore size is the same for CF2 & CF3 2.5V6 (The Diesels also used the same bore).
3.2 was bigger.

Are you single turbo, or twin turbo (with one turbo per bank)?
Thx david and its a Single turbo and the pipe im looking at now is 54mm ID that removes center box.

And not sure if its better to go single pipe from turbo into the dual cat then back to single pipe and out . or single from turbo then through single cat and out
 

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I don't know if the two small Cats of the CF3 unit would flow better than the bigger single Cat of the CF2, but as you have a single turbo (with I'm assuming a single outlet), then you'd have to split it to use the CF3 which may use up any flow gained anyway!

The CF2 Cat is the simplest route and simple is always a nice direction to go.

With it mapped nicely at the no load MOT rev ranges I'm sure emissions would be fine.
As VW have shown, you can get some highly polluting engines to pass MOT style emissions tests..... :soapbox:
 

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Discussion Starter #5
I don't know if the two small Cats of the CF3 unit would flow better than the bigger single Cat of the CF2, but as you have a single turbo (with I'm assuming a single outlet), then you'd have to split it to use the CF3 which may use up any flow gained anyway!

The CF2 Cat is the simplest route and simple is always a nice direction to go.

With it mapped nicely at the no load MOT rev ranges I'm sure emissions would be fine.
As VW have shown, you can get some highly polluting engines to pass MOT style emissions tests..... :soapbox:

Thx again david

You are right simple is best if fairly much same end results , And you have put my over working mind to rest with the MOT. :thumbup:
 
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