Can I expand this y-pipe outlet
Can I expand this y-pipe outlet I am once again looking at the Dynatech Supermaxx header system. The y-pipe has 2.5” inlets and a 2.75” outlet. Do you think it possible to expand the outlet to 3” using one those ~$30 exhaust pipe expansion tools? 
It would be nice if the two sides flowed into 3” instead of a 2.75” pipe, especially if the rest of the system back is 3”. The pipe is 16ga T-304. Even if I can expand some of the outlet, I wonder if it will be possible to expand the portion of the y where the legs are welded together.
On a related tangent, what would be better: mandrel-bent 2.5” or non-mandrel-bent 3”?
It would be nice if the two sides flowed into 3” instead of a 2.75” pipe, especially if the rest of the system back is 3”. The pipe is 16ga T-304. Even if I can expand some of the outlet, I wonder if it will be possible to expand the portion of the y where the legs are welded together.On a related tangent, what would be better: mandrel-bent 2.5” or non-mandrel-bent 3”?
Thank you for the responses. I do not claim to know much about flow dynamics, but I have been operating under the impression the 2.5” is a sufficient exhaust pipe diameter for 500hp or less, as long as there are two of them. Is that premise incorrect? Stated another way, in a single exhaust setup, do I need to size my y-pipe legs so that they have no less than half the cross-sectional area of the exhaust past the y?
Some numbers I have been considering. This assumes 115cfm per square inch.
3.5” = 1106cfm
3” = 812cfm
2.75” = 683cfm
2.5” = 564cfm
Dynatech PowerCat (2.5”) rated flow = 396cfm
I like the fact that the Dynatech SuperMaxx system is all stainless, fits well, and preserves ground clearance. I really do not like the cats or the 2.5”-in/2.75”-out merge. I will have to check my WS6 intermediate pipe to see if it is reduced to 2.75” at the inlet. I was assuming it was 3” along its entire length.
Some numbers I have been considering. This assumes 115cfm per square inch.
3.5” = 1106cfm
3” = 812cfm
2.75” = 683cfm
2.5” = 564cfm
Dynatech PowerCat (2.5”) rated flow = 396cfm
I like the fact that the Dynatech SuperMaxx system is all stainless, fits well, and preserves ground clearance. I really do not like the cats or the 2.5”-in/2.75”-out merge. I will have to check my WS6 intermediate pipe to see if it is reduced to 2.75” at the inlet. I was assuming it was 3” along its entire length.
you ideally want a larger diameter pipe leading into the Y because the gasses are still quite hot and are fully expanded. As you go further down the exhaust, the gasses cool and then dual 2.5s will support 500+ hp. Up front Id still try for 3".
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