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Butterfly Valves Instead of Poppet Valves

Using Butterfly Valves in an Engine Head
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Why are butterfly valves not used for inlet/exhaust valves in a car engine? If they were propperly built, they could seal better and require less force to move than conventional poppet valves.

With propper linkages, you could open all the exhaust valves at the same time with a single cam. Or electro-magnetic actuators could be used, either linear solenoids or rotational motors.

Butterfly valves would also allow five or more valves per cylinder more easily than with conventional designs, as well as different-shaped heads. The valves would also allow more linear flow of the gasses than with poppet valves.

I'm sure someone will tell me why this won't work.

discontinuuity, Jun 03 2005

For [Ling]: Coates Spherical Rotary Valve System http://www.coatesengine.com/
Are you referring to something like this? [half, Jun 03 2005]

[link]






       I doubt they could take the pressure. Poppet valves just get tighter as the pressure builds. Plus, they're more forgiving of build tolerances.   

       Why would you want to open all of the valves at the same time?
RayfordSteele, Jun 03 2005
  

       Well, all the valves that need to be opened. If you make them beefy enough and machine them properly, it could work. Maybe if they were hemispherical so they would push out on the sides and seal it properly.
discontinuuity, Jun 03 2005
  

       That's more like a ball valve?   

       What would be interesting (to me anyway), would be a ball valve that continuously rotates in one direction.
Ling, Jun 03 2005
  

       half, Ermm....yes, exactly that.
Ling, Jun 03 2005
  

       Happy reading then. :)
half, Jun 03 2005
  

       I think Honda had a similar rotary valve system. It would create a wierd shaped combustion chamber, though. And I meant just a slight dome, not a ball valve, but all ideas about rotary valves are welcome.
discontinuuity, Jun 03 2005
  

       The valves would not rotate continously like the ball valve design in the link. They would rotate only when they needed to open or close, and would be activated by a mechanical system (cams, pushrods, etc.) or by some kind of electric motors/solenoids.
discontinuuity, Aug 09 2005
  

       Simply put, butterfly valves are great for a throttle body, but not for intake and exhaust valves. One thing to keep in mind is the less valves the better. As long as you can flow the necessary volume of air. More valves = more trouble. Also, if they didn't rotate contiuously, it would be extremely difficult to get it to open and close correctly without problems. That's sort of the problem with poppet valves, they have to start and stop very quickly, without damaging anything. That's why cams are shaped the way they are to slow them down before they slam down on the head. But, the basic idea is cool, just not practical.
MarcStinebaugh, Mar 09 2007
  
      
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