05 exhaust diameter questions

JustDandee

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since the dawn of time, man has pursued how to go faster, even with a tractor motor....😁

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Jezza

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I wish I had some dyno data to back it up, but I really did feel a low end loss of power when I went from stock system to a Magnaflow full 2.5" system from exhaust manifold back (including new cat) in my '97 4.0.

Edit: I noted similar butt dyno INCREASE in low end power when I went from a JBA header (3-2-1) to a Banks header (6-1) with my 4.6 stroker. That one I do plan to get some dyno data on.

I think most folks would be hard pressed to "feel" the difference. I used to spray a 35 shot on a bracket car years back. You could barely feel the difference when the nitrous hit. 10 or 20hp would probably be invisible to most butt dynos.
 

bluescapegoat

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2.5 " Why start out limiting potential ? If you had a V-10 , ( 488 c.i.d.) Dodge pickup would you put 2.25 dual exhaust on it ?
However , if you believe that you "NEED BACKPRESSURE " to run right why not go with a 1" system for that locomotive type torque. :rolleyes:

I've got dual 3" front to back on my 505 cubic inch Dodge pickup.

But the TJ has a 2.25" on it lol. To be honest I don't know how I ended up at 2.25" though, that exhaust has gone through so many iterations it's probably just what I had laying around
 
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Woodrow

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I think most folks would be hard pressed to "feel" the difference. I used to spray a 35 shot on a bracket car years back. You could barely feel the difference when the nitrous hit. 10 or 20hp would probably be invisible to most butt dynos.

Yep. Butt dyno may be mostly placebo (you feel what you expect to). Interestingly, I was talking to a tuner today who said he has repeatedly seen increase in torque from 1500 RPM on up with open headers vs any exhaust 🤷‍♂️
 

Ericshere03

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Yep. Butt dyno may be mostly placebo (you feel what you expect to). Interestingly, I was talking to a tuner today who said he has repeatedly seen increase in torque from 1500 RPM on up with open headers vs any exhaust 🤷‍♂️

And there are those who swear open headers make less power than full tunes exhaust …
 
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LONGJP2

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Ericshere03

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Another datapoint the 4.9L straight 6 Ford tractor motor typically sees 3” exhaust piping as a “performance” upgrade. And they “feel” lazier than our motors … I’d say a 4.0 feels peppy compared to a 4.9 Ford … but Ford folks swear by them
 

JustDandee

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I was thinking they also did one comparing exhaust tubing sizes; and IIRC, it didn't matter much.

Season 5 episode 16 was The one I was thinking of but The 2.5 vs 3“ I found on YouTube. Higher rpm’s max HP is going to like bigger pipe- of course they are running higher HP stuff but engine Dyno is picking up at 3000 rpm up so leaves room for some speculation what is happening below…