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Discussion Starter #1
I have a 3 inch downpipe, into an 2.5 inch y pipe.

After the y pipe it’s oem piping 2.25 on both sides, to my axle backs, the axleback is also 2.5

So 3 dp to 2.5 y to 2.25 pipe to 2.5 axle

Do you think I should replace the 2.25 oem pipe with 2.5 so its 2.5 from downpipe fully? I figure the pressure going from high to low to high could cause interference in flow

But it’s also past the Y so the 3 inch pipes gas is split in half and may not be bottle necked anyway

Not sure if it would sound or perform any different with full 2.5 or with the 2.25 in line


My set up
Cvfab catted 3.0 downpipe
Roush y pipe 2.5
Oem piping 2.25
Awe Axle back 2.5
 

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The stock is not a restriction in these cars until you start make a lot more power than stock. I would venture that the exhaust you have likely won't present a restriction until you get close to 400WHP.

I have tried all different exhaust configurations between my 15 and 17 Ecoboost Mustangs and none of them made enough of a power difference that my butt dyno could feel. I have settled on 10" long by 6" diameter race mufflers with the stock resonator to get the sound i want.

Dave
 

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Discussion Starter #3
Do you think there would be any improvement if I changed the y pipe to 3 inch so it would be 3 in all way to the split? I could get a 3 inch y made at local exhaust shop instead of 2.5
 

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I really think you're overthinking this..........

Two 2.25 inch diameter pipes have 12.5% more cross sectional area than one 3 inch diameter pipe and 62% more area than a single 2.5 inch diameter pipe. While other factors like bends and connections can have some effect on flow capacity, in this case they are relatively minor compared to cross sectional area. So, the two 2,25 inch section of pipes should not be an issue. The 2.5 inch y pipe probably presents less restriction than a cat converter, when you think of what is inside a cat. Plus, the exhaust coming out of that engine has to pass through the exhaust manifold and has to drive a turbo as well - before it even gets to the "exhaust system".

Adding exhaust flow capacity beyond what the engine actually requires will gain nothing in terms of power.
 

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Discussion Starter #7
Yeah.. I just wanted to get as close as I could to a real Turbo-Back, exhaust but I think what I have is sufficient overall for everything. 2.5 should flow just fine under WOT
 

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Yes, I think so - see my additional edit comments above....
 
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Discussion Starter #9
I really think you're overthinking this..........

Two 2.25 inch diameter pipes have 12.5% more cross sectional area than one 3 inch diameter pipe and 62% more area than a single 2.5 inch diameter pipe. While other factors like bends and connections can have some effect on flow capacity, in this case they are relatively minor compared to cross sectional area. So, the two 2,25 inch section of pipes should not be an issue. The 2.5 inch y pipe probably presents less restriction than a cat converter, when you think of what is inside a cat. Plus, the exhaust coming out of that engine has to pass through the exhaust manifold and has to drive a turbo as well - before it even gets to the "exhaust system".

Adding exhaust flow capacity beyond what the engine actually requires will gain nothing in terms of power.
How much louder should I expect going from dp 2.25 bottleneck to my 2.5 y pipe? It’s now going to be 3.0 to 2.5

mathmatically, your numbers of 62% dual2.25 being bigger than a single 2.5 means one 2.5 pipe has 19% more flow than a single 2.25
 

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It should be louder, but having no direct experience with a 3"downpipe, not really sure how much. Perhaps someone who has will chime in....

With that new "hardware", I would think your exhaust setup would certainly meet/exceed your engine's flow requirements. Will be looking for your post-install review:)
 

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Discussion Starter #12 (Edited)
Replacing y pipe

y pipe from American muscle claims 2.25 y pipe everywhere elsesays2.5

I feel ripped off

gonna go get a 3 inch y made and reduced into 2.25 ends
 

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Discussion Starter #16
LOUD!. super loud. sounds great, throaty too. I was going to post a full video thing today but, I had a bad experience trying to flash my car today. I will try this week.


No regrets. Other than worrying it won't play well with my ford performance tune.
 

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2016 Vert, SCT/Bama Tune, Eibach Sportlines, Boomba T/B spacer, Ford Perf Strut Tower Brace
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LOUD!. super loud. sounds great, throaty too. I was going to post a full video thing today but, I had a bad experience trying to flash my car today. I will try this week.


No regrets. Other than worrying it won't play well with my ford performance tune.
Would love to hear the sound clip if you can post it. You're doing almost exactly what I'd like to do to my 2016 EcoVert.
 
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