9N3 GTI Downpipe and Lambda Sensors

[PoloGIT]

Thanks guys. So if I install a Milltek decat downpipe (for argument's sake), and am running two healthy sensors with standard or CC phase 1, can I expect to have a CEL due to cat efficiency issues? Depending on who you speak to here in NZ, a CEL can mean you fail the warrant of fitness for road worthiness I'll check that though.

Cheers

[h100vw]

Thanks guys. So if I install a Milltek decat downpipe (for argument's sake), and am running two healthy sensors with standard or CC phase 1, can I expect to have a CEL due to cat efficiency issues? Depending on who you speak to here in NZ, a CEL can mean you fail the warrant of fitness for road worthiness I'll check that though.

Cheers

If you do the downpipe, you want Phase 2 to make the most of it. The cat wouldn't be the restriction if you got one with a cat fitted. The std exhaust would be the choke point.

A 200cell cat will stop the light coming up anyway, most likely.

No idea about the ins and outs of road worthiness in NZ but tbh there's no need to run catless or have the light on.

Gavin

[PoloGIT]

Thanks Gavin, I didn't realise the Cat could be that efficient. The additional NZ$500 for the Cat version of a Milltek is probably the choke point for me though, unless you've got some other suggestions? I guess the other question is how noisy is a de cat pipe going to be? Now that I'm "middle aged," I don't particularly want to be blaring around like a bogan when shuffling from A to B! I'm already surprised at how relatively serious the standard exhaust is, although maybe that's something to do with the 220k it's done...

[h100vw]

Thanks Gavin, I didn't realise the Cat could be that efficient. The additional NZ$500 for the Cat version of a Milltek is probably the choke point for me though, unless you've got some other suggestions? I guess the other question is how noisy is a de cat pipe going to be? Now that I'm "middle aged," I don't particularly want to be blaring around like a bogan when shuffling from A to B! I'm already surprised at how relatively serious the standard exhaust is, although maybe that's something to do with the 220k it's done...

No exhaust shops nearby that can make you a downpipe? Downpipe Hosenrohr 63 5mm Polo 9N 1 8T GTI Seat Ibiza Cupra FR 1 8T | eBay

[PoloGIT]

Downpipe Hosenrohr 63 5mm Polo 9N 1 8T GTI Seat Ibiza Cupra FR 1 8T | eBay

That was looking like a great deal - minus the 19% VAT and only 42 Euros to send to NZ - but then they informed me it's a decat pipe Another 169 Euros for the sports cat, which I guess is still pretty good and it's probably what I'll get when I've got the funds. Will have a look locally at what the options are for a custom pipe.

Cheers

[noone]

I have a good 2.5" cat, cheap if you want, PM me if interested.

[PoloGIT]

I have a good 2.5" cat, cheap if you want, PM me if interested.

Certainly. PM sent. Cheers.

[Blue9N3]

Pologit, cats weren't mandatory in NZ a few years ago, dunno about now. Me and most people I knew back then ran catless. Better to just get a custom turbo back exhaust made up out of mild steel than a milltek. Where are you located?


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[PoloGIT]

They still aren't for this vintage of car - I think it is cars registered from 2010 onwards that must have one. Have also found that a check engine light isn't a problem for warrant of fitness - although I'm sure I got hit with that in the past. Anyways, this thread has me tending towards a Cat for the following reasons...a bit quieter, there is negligible performance impact with a sport cat, the ECU won't throw a CEL due to cat (in)efficiency and I am ever so slightly environmentally conscious...

Any reason for mild steel over stainless, apart from being cheaper of course? I guess it would be easier to join to the rest of the mild steel exhaust.

I live in New Plymouth.

Cheers

[sambb]

No I wouldn't get too excited there.
I may be wrong or I may have misunderstood the course of the thread so far but I'm pretty certain that if you are phase 1 and you run a de-cat you will get a cat code. You would definitely have to run a spacer to have a chance of avoiding it but still might be likely to get one even then. For example I was advised by Carformance that they sometimes even see 100 cell people get codes that are running a spacer so that suggests to me that you'd be running the gauntlet with a proper de-cat pipe. If you don't run a second o2 sensor spacer then you may be ok with a 200 cell cat (since they still represent some flow hindrance) but a 100 cell will most likely code. I was advised to go 200 cell with a spacer by Carformance to be sure.
Gav was talking about Phase 2 before which codes out the cat error so that it will be ignored by the ECU. If your on phase 2 you can have any cat you want or no cat at all and it won't matter. Phase 1 tune is expecting to see a Cat though.
My two cents.....If the ecu will throw a code when you have no cat versus when you do have a cat, then it stands to reason that there is still a significant flow difference that the prescence (or lack thereof) of a cat makes . Cats will dull dB's but they are not designed to do this so I wouldn't keep one in the system for that reason alone. If you don't have to have a cat by law, then save the dollars, run the de-cat pipe for best possible initial flow, keep the resonator in place to stop low rpm droning, and throw some money at a new high flow muffler. Yours is most likely flogged by now and a restrictive sponge compared to some really high flowing yet extremely quiet mufflers that are around now. Thats probably the cheapest way into some quiet free flowing-ness! Spend 30 bucks on the correct second 02 sensor spacer and you'll probably be lucky.