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Engine Valve Opening

 Unique Exhaust valve opening
  (+2, -6)
(+2, -6) 		  [vote for,
against]

In my previous post I did not mention my idea clearly.Sorry Guys. I will try to put it clearly here.

In a conventional engine,the exhaust valves are pushed down by the cam lobes to open it. My idea is to pull the valves out of the cylinder.And it can be done in a Camless engine by electro-mechanical valve actuation method.I do agree that during engine firing the valve will open.But why is it not possible to prevent this by energising a solenoid and giving pressure from the top? Please give me your valuable suggestions.

—candidkhalid, Oct 05 2006

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       Are you going to pull the valves INTO the cylinder? If not, then all the earlier objections apply. Look at an engine valve and its matching seat. Notice how they are mating cones, with the large end to the inside. To open the valve moves into the cylinder. To close it moves away until it meets the seat. The engine firing thus presses the valve more tightly closed.   

       Are you proposing reversing this? So that the mating cones open away from the cylinder? If so, the firing of the engine is going to push the valves open, rather than closed. The valve and linkage is going to need to be MUCH beefier to resist this.   

       If the valve is not very tightly closed, then burning fuel air mixture will leak through the valve and seat. Not only will this lose power and contaminate the intake mixture, it will also erode the mating surfaces of the valve and seat, making the problem worse over time.   

       Think about how carefully you have to work while lapping valves. That precise mating is what keeps the entire charge of fuel pushing on the piston.
—Galbinus_Caeli, Oct 05 2006
   

       OK so you're still pulling the valves open. I'm assuming that you're pulling them out of the cylinder, so that the mating cones need to be reversed. As [Galbinus_Caeli] stated, this will be bad, as cylinder pressures will tend to unseat the valve, rather than seat it more tightly. I fail to see how electronic timing will remedy this. my [-] stands.
—Freefall, Oct 05 2006
   

       Maybe, just maybe, it could be done. But it wouldn't be worth doing, really. There is no gain for all this pain. [-]
—baconbrain, Oct 09 2006
   

       Posting the idea again doesn't make it better. Sure, you could do it. Why would you bother? You can't keep them sealed during firing.   

       Consider: at compression ratios of just 8:1 - and most engines run higher than that nowadays - your peak cylinder pressure before ignition is around 120 lbs per square inch absolute. Now let's explode the fuel.   

       Can we design a solenoid that'll hold that valve down against the pressure? Sure. Can we design a cam system that will hold it down? Sure. Can we make it keep the valve tightly sealed during the ignition sequence? No. Not for long, anyway. The cams will gall, the solenoids will overheat, and one engine ping in the right spot and you can wave goodbye to that valve as it exits the car via the hood.   

       It's not a unique valve opening. They're poppet valves that have been installed incorrectly.   

       My valuable suggestion: please let this bad idea die.
—elhigh, Oct 14 2006
   


 

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