Is stock downpipe on MK6 really that restrictive (vs say R MK7)/K04 on stock exhaust?

[coolbaskin]

Stage 2 tunes and higher all require free-flowing downpipe with a "sport cat(alytic converter)". All K04 turbo kits from well-known tuners do list it as a prerequisite. I get it, I get it, stock cat is restrictive and is designed for emissions, not performance, car needs to breathe...


But say, stock R MK7 makes almost 300 HP from the next generation of the same engine. The engine internals changes between generations seem evolutional, so it looks like most of the 100 HP difference comes from bigger turbo and better fueling. But a bigger turbo (more flow) and more fueling means more exhaust gases, too. And they have to go through the downpipe. The car is stock and European, so the downpipe is designed viewing emissions as a very important consideration. If fact, it's designed for newer and stricter emission standards. So it likely has the same if not more restrictive catalytic converter(s?). And it flows more exhaust gases. Hence it seems that either the GTI MK6 stock downpipe is not that restrictive, or R MK7 magically (or not magically, but how exactly?) flows more through the very similar downpipe/cat (how?), or my logic is wrong somewhere. Any ideas?


What I am trying to figure out: I think having extra fun personally (extra power from catless downpipe) for the price of the harm done to everyone (extra emissions) is unfair. So I am trying to find my own way (stock DP? stock DP + better cat welded in? retrofitting stock DP from higher-power sibling?) . Not trying to convince anyone or rage wars, just "not on my watch car". And if it is possible and worth it to go from stock IHI => K04/F23T/Big Turbo... given all the backpressure and melting the catalytic converter considerations. Anyone did it? What's he experience? I take it custom tune would be required, right?

 

[Alpinee30]

You cannot compare them at all they share is the fact they are 2.0L that's basically all and EA.888 in the name The dual VVT and fuel system and cylinder head design. It has way more Deveopment.

I think you could run a K04, and a stock downpipe get a pro tune. Contact stratified I doubt you'll Make 300whp probably about the same as a MK6 R stage one file.

There's a lot of sports catted downpipes, that you Can use it doesn't have to be Cat less. There not cheap. IF you don't want it to stink.

 

[coolbaskin]

You cannot compare them at all they share is the fact they are 2.0L that's basically all and EA.888 in the name The dual VVT and fuel system and cylinder head design. It has way more Deveopment.

I think you could run a K04, and a stock downpipe get a pro tune. Contact stratified I doubt you'll Make 300whp probably about the same as a MK6 R stage one file.

There's a lot of sports catted downpipes, that you Can use it doesn't have to be Cat less. There not cheap. IF you don't want it to stink.

Why not? From all the descriptions I saw, they were more evolutional, then revolutional. Making small changes to improve the main formula, fixing problems found in previous versions, making good things even better. Port injection for more efficiency and valve cleaning. Valve lift to have good performance in low and high RPM, playing with sizes, shapes, and materials, integrated exhaust manifold in EVO (4th gen) ... But still, more HP = more exhaust gases, so what changed in the downpipe?

I do think I could run K04 on stock, too. And I thought about Stratified particularly because they are in a driving distance. The question is "how well" and if it would be worth the trouble to install. Not 350 HP (APR Stage 3) for sure. But say... maybe 300 on 91 octane (with porting/polishing, turbo blanket, ceramic coating for exhaust manifold)? Still a meaningful increase over Stage 1+ I have now (257 HP). Maybe I should ask Stratified first?

Yes, there are catted downpipes, but they have much less effective cats. At best, they are processing the bare minimum of the emissions, some even throw CELs without ECU changes. Metallic sport cats have 200 cells, ceramic -- 400 . Stock DP has 2 x 600 cells according to my research. I do want the DP to provide the stock (or better) level of exhaust cleaning.