Does an h-pipe or x-pipe act as a reverb point? Like open air or a chambered muffler? A program I was playing with said I need about an 18" collector for the truck, and a 14.5 for the car. My x-pipe in my car is way back behind the transmission. Do they HAVE to be placed within the hot gas area, or do they work the same as an open box?

For example, say you are building a tuned header extension and you need it to be 16". It will work the same if you have it 16x2, 16x3, 16x4, ie, 32", 48", 64". Does an x-pipe follow this same rule?

When I dyno my car here this month, I'm going to dyno it with full exhaust, open header, and a set of "tuned" extensions.

What effect does a y-pipe have on collector length?