powervalve question

[salty21]

what is the purpose of having a powervalve. ie why not just have the exhaust port pemanently open?
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04 NSR 125(sold) ---- 03 CBR 600rr(sold) ----90 pan euro ST1100 '' ----02 CG 125
94 CB400 Super Four ---- 2000 VTR SP1 (sold) ---- 08 ninja p8f(sold, meh) ----05 CBR600rr

[NSR Mick]

It's to give the bike some midrange. I'm sure Keith will be along shortly with a more technical answer.
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If you dont like the way that I ride.......Stop trying to keep up!!!

[Kickstart]

Hi

Exhaust port is open all the time that it is uncovered by the piston. However at different revs the port wants to be uncovered at different times to produce best power. The power valve effectively moves the top of the exhaust port, depending on revs, to produce more power at those revs.

Just like variable valve timing on 4 stroke cars.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[salty21]

would it do any damage to leave a powervalve open all the time as mine is a bit sticky
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04 NSR 125(sold) ---- 03 CBR 600rr(sold) ----90 pan euro ST1100 '' ----02 CG 125
94 CB400 Super Four ---- 2000 VTR SP1 (sold) ---- 08 ninja p8f(sold, meh) ----05 CBR600rr

[Kickstart]

Hi

No, no damage is likely to occur. Just expect stuff all low down power and a noisier exhaust. And the longer you leave it the harder it is likely to be to unstick the valve.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[alains]

when the valves are partly closed the torque is improved . it's a question of timming between fresh mixture in and burned mixture out .if you had no exhaust and no powervalve , after burning the mixture , part of the fresh mixture will be out with the burned mixture . if you stop burned mixture , fresh mixture cannot go out . so when the power is closed it blocks the burned mixture partly , the rest is blocked by the pipe and this is why the pipe is also very important . you can try to unplug you servo-motor , put manually your valves fully open and have a run . you will see the result : some problem to put the revs up between 2000 and 7500 rpm
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