S4 100cpi or 200 cat

[HibiscusS4]

Done a few searches and have decided on the XS power ebay exhaust down pipes but they come with 200cpi cats whereas Zinram and Miltek have 100cpi. Is 100 cpi enough for a UK MoT and to keep the error code light off?

I am going to look at welding a flexi in place so was thinking I might just buy the straight through pipes and 2 100cpi cats and weld it all together if 100cpi is enough.

Conversly is it worth the effort for a car thats never going above stage 2? Keeping K03's so would 200cpi be fine for this and save the time and money of fitting 100cpi ones?

Cost comparison is about £50 more plus 2 more welds to fit the 100cpi cats.

 

[jcb]

100cpi cat on my TQS was plenty for 5 MOTs it went through

depends on the Car, the CAT and the test on the day though!
what CO levels are you getting now?

 

[HibiscusS4]

I'd have to check. I beleive the distance from the engine to the cat also makes a difference as its what heats the cat up and increases its efficiency. If anyone with an S4 has any experience of 100cpi that would be proof enough for me.

From what I have read the 200 cpi is prefered for the American market as they have tighter controls. I was more interested in if the 100cpi was a reall difference, if its not then it saves me some extra work.

Also considered what I have read up about called Piggies. Gut the precats and leave the secondary (400cpi?) cats. To do this properly you then have to weld a new lambda boss after the secondary cats.

I am interested in the shortest down time though as the wife uses the car every day. Another consideration is that I have heard you can weigh in cats for good money so if I smash the cats out the stock manifolds it could actually cost me money compared to changing them comleatly. If what I have heard is correct a stock exhaust setup is worth £120 as it has 4 cats.