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Buell Forum » XBoard » Buell XBoard Archives » Archive through December 01, 2004 » Xb12 headers on the Xb9 « Previous Next »

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Cataract2
Posted on Thursday, November 25, 2004 - 02:42 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Has anyone tried this yet? If so how were the results?
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BadS1


Posted on Thursday, November 25, 2004 - 02:58 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Been hashed over and won't work well.
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Cataract2
Posted on Thursday, November 25, 2004 - 08:11 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Because?
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Spooky


Posted on Thursday, November 25, 2004 - 09:42 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Do a search and you will find!!!!
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Ingemar


Posted on Friday, November 26, 2004 - 03:36 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I think it was because the diameter is bigger so they provide less backpressure, which in turn results in less bottom end power. I don't know if it would help top end though.
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Porker
Posted on Saturday, November 27, 2004 - 01:45 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I think it boils down to math. You need a certain diameter exhaust manifold for certain hp figures and again for displacement reasons. If a 9 put out 120 + at the rear wheels with stock displacement you would NEED larger headers. In stock config though going bigger is going backwards IMO.
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Static
Posted on Saturday, November 27, 2004 - 03:19 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

"I think it was because the diameter is bigger so they provide less backpressure"
sort of. It's basically a matter of exhaust pulse timing and velocity. Behind each high pressure exhaust pulse is a low pressure area that follows. The idea is to have a low pressure area help extract the next exhaust pulse from of the combustion chamber in turn helping pull a greater air/fuel charge into the combustion chamber. This is called scavenging.
Pipe diameter directly affects the efficiency of a given engine in a particular RPM range. Larger diameter pipes typically increased higher RPM power at the expense of low end torque.
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Racertroy


Posted on Saturday, November 27, 2004 - 12:18 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

for what it's worth, i've heard it will work better than stock if you mock up some reversion cones and weld them it...don't know any more than that...but if you can pick some up cheep...may be worth the time and sheetmetal...

good luck,

--ts
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Ingemar


Posted on Saturday, November 27, 2004 - 12:21 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Thanks for that explanation Static.

Larger diameter pipes typically increased higher RPM power at the expense of low end torque.

So what we need to invent is a dynamic pipe diameter that increases when rpms go up
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Slaughter


Posted on Saturday, November 27, 2004 - 12:42 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

So what we need to invent is a dynamic pipe diameter that increases when rpms go up

Kinda what the factory is selling on the 12? Variable back pressure controlled by the ECM.

...Next question! ; )
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Ingemar


Posted on Saturday, November 27, 2004 - 01:46 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Oke.

Is a longer pipe the same as a wider diameter header?

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Static
Posted on Saturday, November 27, 2004 - 03:59 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

"Is a longer pipe the same as a wider diameter header?"
Not exactly. in fact a large diameter longer runner length will in some ways act like a smaller diameter shorter runner. (though the details are much more involved) Remember that you are tying to maximize volumetric efficiency within a specific operating range.
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