4inch vs 5inch exhaust - Ford Powerstroke Diesel Forum
6.4L Performance Parts Discussion What has or has not worked for you?

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post #1 of 7 Old 02-08-2010, 04:50 PM Thread Starter
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4inch vs 5inch exhaust

Is there a big power difference between a 4 and 5 inch system? it seems to me that there wouldnt be because your bottle necking the exhaust flow through a 4inch downpipe. what are your thoughts???

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post #2 of 7 Old 02-08-2010, 05:18 PM
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As I understand it, no. It's mainly a deeper sounding exhaust then the 4in but the power stays the same.


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post #3 of 7 Old 02-08-2010, 05:21 PM
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Not sure on power but 5" is louder. and a larger 4" down pipe makes it louder as well.

2008 F-250 FX4

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post #4 of 7 Old 02-08-2010, 05:21 PM
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As far as I know there is no difference, again sounds better then 4". I was told once that u loose a little power with the 5". I don't know if thats true or not.
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post #5 of 7 Old 02-08-2010, 05:34 PM
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i have never seen a dyno sheet comparison....i seriously DOUBT you lose any power ...

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post #6 of 7 Old 02-08-2010, 09:24 PM
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There should be no power loss, and really no power gain. It will move more air post turbo, have a deeper and slightly louder exhaust note, and it will MAYBE lower EGT's at WOT and lower them quicker at idle.

Jeff Dodd

2012 Ford F-250 Lariat CC/SB

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post #7 of 7 Old 02-09-2010, 12:28 AM
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THere is little difference in performance between a 4" and 5" system. As noted in KTM rider's post, the downpipe IS the restriction. The stock downpipe on these trucks is really closer to 3" id, what you are looking at on the outside dia at about 4" is the outer wall of a double wall pipe. While a 5" exhasut will give a slightly deeper sound, the downpipe is where the restriction is.
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