Exhaust header configuration

[Lachie04]

HI guys, new here on this forum been bumping around Katriders for a while but as I have a project bike going on at the moment and wanting some info thought I'd put it to the brains trust

So my project includes a tweaked over gsxr750 '89 motor and am getting a new stainless 4-2-1 made up for it.

Looking through some performance mod's for the exhaust and there is quite a lot of support out there the correct (or better) pairing for the headers is pairing 1-4 & 2-3 together so this brings the pulses/scavenging back to an even 360° on a 180° crank.

Wondering if anybody has ever had any experience with this pairing and outcomes, according to many it's supposed to even out the torque curve.

yes it may look a bit strange but then I am too LOL

Edited February 15, 2018 by Lachie04

[Gixer1460]

Only seen it done commercially a couple of times - one was a Yoshimura for a 400/4 - looked very odd. Often done with turbos to even out the pulses but for a NA pipe I'd doubt its effectiveness. Best pipe I had was built for the bike, was a 4-2-1 system with 1-2 and 3-4 pairing but very long primaries and short mid pipe link - made a near flat torque curve.

[Lachie04]

Heres a couple of recent Yoshi examples I've found for the GSXR1000, maybe this tech is not dead 

Yoshi's spin is "dramatically improves power and torque across the entire rev range"

Interestingly the second one also includes a balance pipe closer to the port which I always thought was there to "re balance" 421 systems 

 

Edited February 15, 2018 by Lachie04

[gsx]

Me gsxr 11 sounded like a twin and was very flat with 1,4 and 2,3 didn't sound any louder with silencer off either , builder did it by mistake when I asked for a 4,2,1 system

[bluedog59]

I have Akrapovic full systems for a B12 and a GSXR1100w, they are both 4-2-1. The B12 one is linked 1/4 and 2/3, the 1100 is 1/2 and 3/4.

It "could" be that,

A. 1/4 and 2/3  suits the torque of the lower revving B12 and 1/2 and 3/4 the higher revving top end of the 1100.

Or,

B.  1/4 and 2/3 is used on the B12 to help boost where it is weak (top end) and visa versa on the 1100 to bump up it's mid range torque.

Time to get some of my tuning books out and do some reading.

[Dezza]

Maybe also a commercial exhaust manufacturer would take into account the 'note' of the pipes they make, which may, for road bikes at least, even be more important than any technical advantage. If a 421 configuaration made the bike sound naff, even if it was technically superior, the manufacturer may decide to go with the 'inferior' option if it made more commercial sense. This would be less likely for products sold for racing though. Just a thought.