what exactly are powervalves??

Sno_Racer_Xtreme

Sno_Racer_Xtreme

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Probably a really dumb question, but what exactly are powervalves? I know they are a special type of exhaust valve, and i know how an exhaust valve works on a four stroke. but i dont know how they work on my srx.

thanks
 
I'm sure there are many others on here who can explain it better, but on a 2 stroke the power curve is partially determined by the exhaust port height. A high port allows high horsepower at high rpm's, but sacrifices low rpm hp/torque. A low port height provides the exact opposite. So until variable exhaust or powervalves came along, manufacturers had to settle for a happy medium, or have a very "pipey" high powered engine, which had a very narrow power band, which is hard to clutch for. Think of an old motocross bike, you could really feel when it "came on the pipe". The power valves allow for both worlds, as they are closed at lower rpm, then open up at higher rpms, allowing the engine to act as if it had high port timing (which it now does with the valves open, exposing the upper portion of the port).
Hope this makes sense.
SRXer
 
maxout01 said:
Sounded good to me!! That's pretty much why only bigger motor/ muscle sleds have them.
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Most 440's, 500's and 600's have them now. They are a great improvement on any engine size. Improved mileage, quieter, more low end power while still maintaining good top end. Only downside is the increased maintenance of keeping them clean and adjusted.
 
From my understanding, They also aid in the ongoing war again emmissions by capturing some of the unburnt fuel/oil mix that 2 strokes are famous for.
 
taylzee said:
From my understanding, They also aid in the ongoing war again emmissions by capturing some of the unburnt fuel/oil mix that 2 strokes are famous for.
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fringe benefit, they where made for power long before they where used to help emissions.
 
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