2.5" y-pipe vs. 3" y-pipe
12-01-2008, 09:08 PM
#1
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2.5" y-pipe vs. 3" y-pipe Hey, everyone. I know that almost all headers for f-bodies come with a 3" y-pipe, but it seems to me that two pipes merging into one pipe, when all pipes share the same diameter, would create backpressure. Could anyone shed some light on the physics of this?? I want to get headers next spring, and am considering either the ARH/ catted y setup, or the Bassani headers and 2.5" y-pipe combo. My car is strictly a daily driver, so I,m really more interested in low end (idle-3500 RPM's) power. Thanks for all replies.
12-01-2008, 09:46 PM
#2
well considering not many make a 2.5" y pipe, i would just go with a 3". i don't think your really gonna notice any difference. there are lots of people on here making big hp with a typical 3" y-pipe
12-01-2008, 09:50 PM
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I did have the Pacesetter/TSP y-pipe setup before, but it felt like it had less power below 3000 RPM's than when it was stock. That is why I'm wondering what effect headers and a smaller y-pipe would have on low end torque.
12-01-2008, 10:38 PM
#6
I started a thread about this a year or two ago in the Advanced Engineering forum and couldn't get much action on it; then it was moved to this forum.
My reasoning is this: All the 3" Y's neck down to a 3" I and then some down to 2.75." A 2.5" Y does the same, so the point of greatest restriction is equal between the two.
I have 3">2.5" reducer cones coming off my collectors to a 2.5" Y into a Flowmaster merge to a 3" I pipe. My theory is that exhaust gas velocity is better served by this gradual reduction in flow, than by running a 3" Y into one 3" bottleneck at the merge.
My reasoning is this: All the 3" Y's neck down to a 3" I and then some down to 2.75." A 2.5" Y does the same, so the point of greatest restriction is equal between the two.
I have 3">2.5" reducer cones coming off my collectors to a 2.5" Y into a Flowmaster merge to a 3" I pipe. My theory is that exhaust gas velocity is better served by this gradual reduction in flow, than by running a 3" Y into one 3" bottleneck at the merge.
12-02-2008, 04:39 PM
#7
I've got a 2.5" y-pipe that merges into a 3.5" i-pipe. Powerwise it put down a hair more than my 3" y-pipe into a 3" i-pipe; if anything I have more down low and much better clearance (I'm lowered). I attribute some of it to the 3.5" i-pipe and 3.5" muffler.
