Exup

Exhuast Ultimate Power Valve , used by Yamaha for many years now . it primary job is to boost torque , the Valve is situated in the exhaust header & opens & closes to boost exhaust back pressure . it is linked to the bikes ECU & during operation the bikes ECU measures exhaust flow , throttle postion etc & then the valve opens & shuts to various openings to boost torque .
i didnt even give it a chance , i disconnected the EXUP system when i installed my GYTR slip on pipe .. :)
 
EXUP (EXhaust Ultimate Power valve) is a device fitted to selected Yamaha motorcycles (FZR,YZF,XV1900,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 (similar to a butterfly valve) inside the exhaust at the point where the four pipes from the cylinders meet. Closing of the valve then creates a venturi effect inside the exhaust system, causing an increase in pressure on the engine side of the exhaust system. This increase in pressure results in greater exhaust velocity. A servo motor controlled by the ECU opens and shuts the valve. The EXUP valve operation goes from being almost fully closed at idle speed, through to being fully open at 9000 to 11000 RPM (2500 RPM for XV1900).
 
I removed the exup from my fzr1000 gave it bit more grunt but lost about 20mph 0n top end speed ive done the same on the fz1 but without a speciffic map for pciii ive got no referance yet
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I'm about to remove the Cat and Exup and replace the stock exhaust with a Mivv GP. It's an '08.

The impression I'm getting is I will experience an increased upper end for sure, with little or no effect on the low end and mid range.

Am I correct?
 
I'm also interested whether I should disconnect the EXUP or not if I'm going to install a Yoshimura slip-on. Extra torque is never wrong, so why do the installations instructions say to disconnect it ?
 
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