snoden700viper
Member
I just want to get it straight. When the valves are fully open they are flush with the inside wall of the cylinder...correct? So at full throttle they are in this position (fully open)? At idle they are sucked back into the valve housing. I guess I'm asking for an explination on how they operate and how the servo motor works and what position the cable pulley is in at operation. Thanks in advance for you're help.
usually, they open around 6000 rpm's (they start to)..and they open up pretty fast!!!! being flush when they are fully open is the way to go!!! If they are NOT fully open, they pose a restriction,,, A restriction slows you down... If they are open too much, you have sharp edges on the exhaust port SLOWING down the exhaust flow.... So POLISHING the ports, especially on the cutouts for the valves is a GREAT idea!!!!! Hope that helps!!! Gary Oles nosboy
Correct they are closed at idle to 6000 rpm because they add restrictions and create backpressure and therefore more TQ at these rpms, when they open up they allow the engine to flow much better creating less restriction and more power up top. They are an awesome concept.
power valves
with the valve in the closed spot, they lower the port timing which creates more bottom end and torq. When the valve opens it advances the port timing by raising the exh. port, this makes more topend hp. Its how yamaha let you have your cake and eat it too.
this technology has been used in formula one cars for years and then found its way to the srx back in 1998, now cat is using the same thing. The servo controller is much more accurate and reliable to the gas operated valves like polaris and doo offer.
with the valve in the closed spot, they lower the port timing which creates more bottom end and torq. When the valve opens it advances the port timing by raising the exh. port, this makes more topend hp. Its how yamaha let you have your cake and eat it too.
this technology has been used in formula one cars for years and then found its way to the srx back in 1998, now cat is using the same thing. The servo controller is much more accurate and reliable to the gas operated valves like polaris and doo offer.
Thanks mrviper much more techincal explaination then my off cuff made up one 
yamaholic22
Active member
the new doo powertek's use electronic controlled valves as well, finally got away from the cylinder pressure actuated bellows.