Downpipe - size?

[Henka]

OK, cool...

Well, I'm DIY all the way. The plan is to build the DP and catback before summer.

[Doug_RS2]

Go for a 3.5" now and you won't wish that you ahd gone with that later when you want more power - get the seperate WG pipe as well.

[auditude]

Go for a 3.5" now and you won't wish that you ahd gone with that later when you want more power - get the seperate WG pipe as well.

I've seen some cars with a tiny exhaust exiting next to the main exhaust at the rear of the car. Let's say someone wanted to run the WG dump pipe all the way to the rear, or through its own cat or muffler or something. Where would they find that small diameter piping? Is there such a thing as a catalytic convertor that small, and if so, would it even work since it needs to be heated up to temp to function?

Where I live we get an underhood and under car inspection for emissions. Luckily all wheel drive cars are tested at idle, versus the two wheel drive cars that have to get a rolling road type of test.

I would probably not even open the wastegate during the idle test, but I have another car that will be a turbo front wheel drive and I'd like to explore the separate WG dump pipe option, but not get in trouble for it.