X pipe H pipe or side by side

Here is another example, the 180 degree header. Each tube is attached to the next cylinder in the firing order. This maximizes the scavenging affect. But these are expensive and sometimes there is not room in the engine compartment to do this. They are popular on boats and racecars because there is plenty of room. Picture the exhaust on an open wheel racecar. Always tubes tuned to the next in the firing order = more power. Tube length and tube diameter affect horsepower/torque peak. The tri-y with steps in the tube diameter accomplish the same thing. We use to adjust the collector length with a yellow crayon. Draw a line along the length of the collector, run the engine and look at where the crayon line stopped melting.