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# Dual Purpose Valves

Use all the engine's valve for intake and exhaust
 (0) [vote for, against]

Note: Although my idea was not inspired by [rasberry re-tart]'s idea, I feel I must link to it because it is similar to this and does use the same name. Also note, if you are not in the mood to read a boring mechanical idea, you will most definately not enjoy this one.

Let us say that an Inline 6-cylinder has 4 equally sized valves per cylinder (2 intake, 2 exhaust). That means that each time either set of valves opens, 50% of the total number of valves are not doing anything and are just wasted space. If all of the valves (in this case 24) could be used for both purposes, the gains in power and efficiency could be great. Although there is no way of accurately estimating, I can throw out the fact that Ford got an extra 52HP out of its Triton 5.4L V8 simply by redesigning the 2-valve heads as 3-valve heads. If the engine size is factored in, it can be rougly estimated that an Inline-6 like the 3.2L one found in the BMW M3 could gain an extra 62HP from doubling its number of intake valves. If you add another 10HP or so from doubling the number of exhaust valves as well, you now have a naturally aspirated 3.2L with an astounding 405HP (333+72), plus 4 intake and 4 exhaust valves. So now that I have explained the "why", I'll explain the "how".

How: Each runner from every cylinder meets with its own tube at a perpendicular intersection, giving the shape of the letter T rotated 90 degrees (clockwise for the runners on the right side, counter-clockwise for the runners on the left). The intake side of each tube would be the top, and the exhaust side would be the bottom. Within each tube, there would be 2 butterfly valves with springs to keep them closed. The intake butterfly valve is mounted just above the runner and the exhaust butterfly valve is mounted just below. When the valves from the engine open and the engine is sucking air in, the exhaust butterfly valve is keep shut by the spring to avoid the engine sucking in exhaust or boosted air from a super/turbocharger (optional) while the intake butterfly valve is kept open by a very, very small electric motor receiving only enough electricity to overcome the resistance of the spring. When the exhaust stroke occurs, the intake valve is kept forced shut by the spring (to avoid boosted air from flowing through the tube or having exhaust blow into the intake manifold) while the exhaust butterfly valve is kept open by a very, very small electric motor receiving only enough electricity to overcome the resistance of the spring.

Potential Problems: Just like camless engines are still not refined enough to use in cars (yet), this engine might have that problem since the valves work with the same basic idea of receiving electricity at just the right time. Also, The Inline-6 cylinder used as an example about would have 2-runners per cylinder. Each runner contains 2 butterfly valves. That engine would need to successfully time 24 butterfly valves correctly.

 — acurafan07, Jan 24 2007

Dual-Purpose Valves Dual-Purpose_20Valves
Similar idea by [rasberry re-tart] [acurafan07, Jan 24 2007]

Impulse Engines [acurafan07, Jan 24 2007]

Illustration http://www.putfile....pic.php?img=4614891
How it could possibly look [acurafan07, Jan 27 2007]

 Interesting idea, although it is really nothing like my own, and probably would work a lot better. If I understand you correctly, you essentially have six valves per cylinder, with a sort of "ante-chamber" or "post-manifold" on top of the head.

 This idea would definately allow for better breathing in an engine, but those 24 (or was it 12?) extra valves might make trouble, and I can see that mixing of intake and exhaust gasses in the "ante-chamber" could be a problem.

 Also, you would have to add thickness to the head to provide strength and cooling passages between the two chambers. This extra space beween the 4 standard valves and the 2 butterfly valves could cause trouble with resonance of the gasses in the runners making valve timing difficult.

This idea is definately possible, but I'm not sure how well it would work. Someone who knows more about physics and fluid dynamics should take a look at this.
 — discontinuuity, Jan 24 2007

 It's the gas path that is all-important in designing a head for high power. More valve area is a good thing, but is only one facet of a good system.

 Your intake and exhaust both have to make 90 degree turns, which causes significant backpressure. There are losses associated with butterfly valves which will also create backpressure. Finally, the engine will re-inhale its own exhaust and will also transfer exhaust heat to the incoming charge, reducing its volumetric efficiency.

I'd suggest that a two-valve head is designed for manufacturability and low cost, while a three- or four-valve head is designed for performance. The increase in numbers of valves will not have been the only alteration to the head if Ford were looking for more performance; the gas paths will have been tweaked for a more efficient, albeit more expensive profile.
 — david_scothern, Jan 24 2007

In thinking about it, the pipes wouldn't have to make a 90 degree angle and in fact could make a very small angle (shaped kind of like this >- ). The butterfly valve would close in the exhaust tube right before the piston reaches TDC specifically to prevent the engine sucking in its own exhaust. Negative supercharging for the exhaust [link] would also suck the exhaust out and make sure that the exhaust and intake gases interfere as little as possible (I believe that the piece about how it has to be used with special valve timing is complete rubbish). As for the backpressure part, I know that many engines are tuned to promote backpressure and use it to make power.
 — acurafan07, Jan 24 2007

Someone did something like that in the early days. It might have been Frederick Lanchester, but I speak under correction.
 — Ned_Ludd, Jan 25 2007

Not trying to bring the idea back to life, but just wanted to note that it is possible to do this without electronically controlled butterfly valves. With a small supercharger, you could have a reed valve in the intake and exhaust tubes. The springs would be set on the intake so that the supercharger pressure alone couldn't blow them open, but combined with the vacuum from the engine they would. The springs would be set on the exhaust so that they would require slightly more pressure than the supercharger boosts to open. This is total would prevent the valves from opening when they shouldn't, but would allow the engine to have automatic valves for this (plus get the added boost of a small supercharger).
 — acurafan07, Apr 01 2007

If you can do this with butterfly valves or reed valves, it might be worth it. If you were using poppet valves, you would have way too much reciprocating mass.
 — discontinuuity, Apr 02 2007

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