EXUP

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EXUP (EXhaust Ultimate Power valve) is a device fitted to selected Yamaha motorcycles (FZR,YZF,R series) that constantly adjusts the internal diameter of the exhaust system to suit engine revs. This ensures good low to mid-range performance for a linear power output all the way to the rev limiter. This is achieved by using an internal valve inside the exhaust at the point where the four pipes from the cylinders meet. Due to the high performance of these particular engines at high RPM, the exhaust valve inside the piston tends to open early. This is beneficial to the performance of the engine at high RPM, but detrimental to performance at low RPM. Closing of the valve then creates back pressure inside the exhaust system, forcing down the piston. A servo motor controlled by the Ignitor module opens and shuts the valve. The EXUP valve operation goes from being fully closed at idle speed, through to being fully open at 9000 to 11000 RPM.