EXUP

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EXUP or (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 perfectly suit engine revs. This ensures massive low to mid-range performance for a linear power output all the way to the rev limiter. This is achieved through using an internal valve inside of the exhaust at the point where the 4 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. Control of the valve is achieved using a servo motor to open and shut the valve, and this is controlled by the CDI. The EXUP valve operation goes from being fully closed at idle speed, through to being fully open at 9000 to 11000 RPM.