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I'll give you the numbers to compare. A set of dual 2 1/2 pipes have a combined surface area of 9.8175 inches, while a single 3 inch pipe has a surface area of 7.0686 inches. Thats quite a bit of difference.



I think you mean cross sectional area not surface area. Those duals have a ton more surface area in the pipes to create friction witch resists flow. Also because the cross section is so much higher in the duals it loses velocity. If you had two exhaust systems of equal cross section then the single would make more power. The single would also be more balanced and scavenge better, sort of like an X pipe but it don't seperate back appart. A single exhaust with an equal cross section will have more velocity, flow and HP. Your examples are not equal though.



All that is true. dual pipes will have MUCH more surface area inside the pipe, creating more boundary layer turbulance/friction and resistance to flow.

a dual 2 1/8" pipe is about equal in cross sectional area to a single 3" pipe.

I would think the dual 2.125" system would have more low end torque, and still maintain the same higher RPM hp of the single 3" system.

I've always read that smaller pipes will have more velocity, more torque, but will not support high RPM flow requirements. Especially with header primary sizes.

if a smaller primary size gives more low end torque/scavenging because of the increased velocity of the flow, but will become "stuffed up" and not support high RPM hp, then why would that not apply to the full system?

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