What is the concept behind a smaller dia head pipe?

yea, like the yosh full system has a header noticeably smaller in dia than stock for the first half of the header.

I realize it is probably affecting the gasses swirling or something like that, but is that supposed to increase top end, low end...somehow increase hp????

700

Compared to a larger head pipe, a smaller diameter head pipe increases gas velocity as it exits the head. It will increase low end/midrange (torque). It also allows for an increase in diameter further back which improves overall scavenging characteristics and top end (rev).

I couldnt have put it better myself

Compared to a larger head pipe, a smaller diameter head pipe increases gas velocity as it exits the head. It will increase low end/midrange (torque). It also allows for an increase in diameter further back which improves overall scavenging characteristics and top end (rev).

Thanks....Just got my yosh full system for my 07, and was suprised to see the smaller dia, and was like &%$#@!!

Compared to a larger head pipe, a smaller diameter head pipe increases gas velocity as it exits the head. It will increase low end/midrange (torque). It also allows for an increase in diameter further back which improves overall scavenging characteristics and top end (rev).
Whether this is true or not depends on the point at which the first upward step in diameter is placed. On old school pipes that were a single diameter over their whole length all the way to the end, a megaphone, or a muffler, smaller, and/or longer, pipes do equate to a lower rpm power peak. But with a stepped header, this doesn't follow as neatly.

A pipe that starts out small and makes the first upward step well back from the head is likely to be biased more toward higher rpm than one that steps up closer to the exhaust port, especially if the second pipe is longer overall.

But you are correct that the smaller diameter increases exhaust velocity, and that increases the effect that each step increase in section has on the way the pipe works.

Hey 700 did you install your pipe yet? Does yoshimura already have an 07 pipe or is it an 06? I wasn't so lucky with my fmf (06 on 07). fmf does not have 07's yet.

Hey 700 did you install your pipe yet? Does yoshimura already have an 07 pipe or is it an 06? I wasn't so lucky with my fmf (06 on 07). fmf does not have 07's yet.

Yes yosh has the full system (same as 06), but the slip ons are all different because the stock headpipe dia at the junction is different than 06

The craftmanship of the yosh is sweet! I am waiting to try it, my suspension is in cali @ MB1

700

Hi,

How much smaller is that diameter ? Could you measure it for me please ?

Timo Mc

Hi,

How much smaller is that diameter ? Could you measure it for me please ?

Timo Mc

What DIA are you wanting....The yosh head pipe @ the head?

700

Hi,

Yes, that would be nice

Timo Mc

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