2-1 vs 2-2

[gregjet]

As you correctly point out the extra HP would be at tuned length usually near top end of the revs. That's why I just bought an Akro as I only ride street nowdays, max HP isn't an issue. I swapped for the drop in weight.
I raced a VTR250 for a while and when I did the maths for the pipes I got huge interference and out of phase problems with the 90/270degree Vtwin pulses. same firing order as the MT/FZ07. I made a set of tuned length 2-2 and 2-1. The 2-2 had 6HP more. When you only have 25HP to start with that is significant. Unfortunately I couldn't get the class "exhast may only be modified from the last join back" rule changed, so I was racing 40HP CBR250RR's with a 25HP VTR250. Those extra 6 ponies would have been useful especially as the VTR was substantially lighter and handled better on the short tight track.

[hordboy]

6hp is really impressive!

[Beemer]

I personally wouldn't care too much if a 2-2 system wasn't "perfectly" tuned just so long as it looked good and sounded good and didn't cause a 'huge' loss of torque or power. I'm old school so I'll take a set with their imperfections and not fuss.
 
 
Yamaha should've made a retro FZ-07 and put 2-2 exhaust on it instead of making that XSR900 triple without 2-2 that doesn't make any sense. I mean a 2-2 is classic, not 3-1 so the FZ07 would've been a better candidate for a retro look.
 
 
 
 
 

[blackout]

So, back to the question whether 1 oxygen sensor is enough in one of the tubes? The computer would only be reading 1 cylinder. Or could another oxygen sensor be wired in parallel with the existing sensor? I don't know.