All Things Mk5 > Performance Modifications

downpipe

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Osd0212:
good morning all!

replacing the turbo on my 2005 mk5 gti, looking at downpipes to put on as part of the replacement. was just wondering if anyone had any suggestions. obviously decat is a lot cheaper but is it worth splashing a bit more and getting a sports cat?

many thanks!

owen

pudding:
Decats are noisy and will put the check engine light on, which you will need a remap to turn off.

A lot of people just knock out the primary cat instead, which is free and improves flow. The secondary cat is enough to pass the MOT but the CEL might still come on if the original secondary cat is old and losing it's efficiency.  It doesn't affect how it drives but a CEL is an instant MOT fail if it's emissions related.

LC5F:
I would recommend the pipewerx sport cat downpipe on ebay, to me they offered the best value out of all the UK made ones' excellent welds and comes with 200 cell Magnaflow sport cat - the next cheapest is £150 to £200 more.

It easily passed MOT emissions, but - as Pudding mentioned - it annoyingly does periodically trigger the CEL for being too good... but for MOT I can delete the code and it wont reappear for a couple of weeks - long term plan is remap.

breeze:
My understanding was that you are never guaranteed a pass with a sports cat and also that they do deteriorate over time, much faster than the factory cats. So you need to have a backup plan come MOT time. That might be swapping to factory or finding an understanding tester, which might be tricky if you have just had a recorded fail for emissions.

I’ve had Milltek cats on another car in the past and I remember the testers needing to spend ages heating it up to get a pass. I’d assume that had a good catalytic section. Welds breaking was the last straw and I swapped back to factory.

pudding:
There isn't anything better than factory for emissions control and build quality.  You certainly won't see a flimsy Milltek last 15+ years/150K+ miles.

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