Has anyone done any back to back testing or comparison between stock headers and aftermarket headers? 4-2-1 vs 4-1? Or versions with shorter primaries? Just swapped this stainless number from my parts bike on to my good one but haven't had a chance to ride it yet because it's pouring down outside.
I'll be keen to see what difference (if any) it makes. I guess the collector being closer to the exhaust valves might draw the combusted charge out a tiny bit quicker and help pull in the new charge, but my thought is that it won't make any difference at all. I will be happy if it does. Also, do those stainless Steel headers have an expansion cone as they attach to the head like the normal ZXR pipes do?
Shorter primaries raise the rpm where the torque peak occurs. The systems appear to have roughly the same overall length so the HP peak will still happen at the same rpm. Without any other mods it'll probably give a slightly narrower power band. Maybe with a sharper entry = which could feel like more power.
It's not a cone, but they do step up in diameter just after the flange. There seems to be a lot of different designs available from the aftermarket, from super long 4-2-1 systems, to 4-2 systems with twin silencers, and long, medium, short primary 4-1 systems Interestingly the new zx25r has pretty short primaries (possibly for packaging reasons) and crossover tubes between each