4 into 1 and stock exhaust/headers

[subforry]

Hi all,

I have been wondering about this for while. 4 into 1 headers make sense since bigger pipes can be used and yet the exhaust air columns remain close and improve the scavenging flow. I see many bikes (including my own) that have replaced the 2 into 1 set with 4 into 1. Why didn't the bikes come with 4 into 1 headers to begin with? Or is 4 into 1 just some bolt-on hype? Or do twin pipes sell better in the showroom?

Thanks.

[posplayr]

Hi all,

I have been wondering about this for while. 4 into 1 headers make sense since bigger pipes can be used and yet the exhaust air columns remain close and improve the scavenging flow. I see many bikes (including my own) that have replaced the 2 into 1 set with 4 into 1. Why didn't the bikes come with 4 into 1 headers to begin with? Or is 4 into 1 just some bolt-on hype? Or do twin pipes sell better in the showroom?

Thanks.

4:1 was a racing innovation to get a hp boost at high RPM due to scavanging effects.

all things being equal (which they are not) 2:1 would provide better mid range but with more weight.

4:2:1 is what most modern street bikes use for improved midrange.