Post Master General
Join Date: Apr 2012
Location: Bowling Green, VA
I Ride: '09 ZX6R
..... in a perfect world, the butterfly would be there as a performance aide. It is in fact a gizmo to defeat the DOT/EPA noise measurement test.
The valve moves to reduce the exhaust pipe area, thus changing back pressure and muffling some of the noise from the engine. It is only rotated into position at 50% max RPM, over a narrow band of RPM. Above and below that narrow span of RPM, the butterfly is wide open. No effect, at any other RPM.
You can simply disconnect the cables from the servo, that move the valve if you want to check that out. The valve is spring loaded to stay wide open.
If you leave the electrical wires connected to the servo, the ECU doesn't know anything's changed. No codes, lights, or changes in performance.
"Basic stuff fellas. Use your head for something other than to break your next fall."