What's your answer to this question??

[CBattaglia]

Similiar questions:
Is a plane 'pushed' up or 'lifted' up? Are F1 cars 'pushed down' by the air foils or sucked down by a low pressure zone beneath the air foil?[/quote]

Aircraft are "Sucked" up due to low pressure created above the wing. A wing is like half of a venturi (which is how your carburator accelerates air intake).

[joey_hv]

Originally Posted by lineslinger

So Joey,
At 26 fathoms are you sucking air or is the ambient pressure in your helmet/suit? forcing it in?

at depth we are using what is known as a "supercharger" pressurizing the air to 150psi above bottom pressure. if we are "sucking" air ....we have bigger problems only time we are "normally aspirated" is on the surface where we open up our lungs and let the ambient pressure fill them up..

[vettestr]

The talks circle back to the piston sucking fuel charge into the cylinder so here is a mind twister to kick around. If the piston is responsible for filling the cylinder what if we increase the size of the intake valve or have 2 or 4 valves per cylinder? If the bore diameter is 4 inch what if the the intake valve was 5 inch in diameter?

If the intake valve was not restricting flow or creating a pressure differential on each side of the valve when opened would the cylinder still get filled if the is no SUCTION? ( bore is 4 " and intake valve is 5 " and very high ramp angle)

[Naumoff]

Originally Posted by vettestr

The talks circle back to the piston sucking fuel charge into the cylinder so here is a mind twister to kick around. If the piston is responsible for filling the cylinder what if we increase the size of the intake valve or have 2 or 4 valves per cylinder? If the bore diameter is 4 inch what if the the intake valve was 5 inch in diameter?

If the intake valve was not restricting flow or creating a pressure differential on each side of the valve when opened would the cylinder still get filled if the is no SUCTION? ( bore is 4 " and intake valve is 5 " and very high ramp angle)

Yes. The air is only trying to balance a pressure differential. If there is no pressure differential the air is already in there or the air will move in without an increase in velocity. The increase in velocity is the specious suction you think about. The air moves in and out of the cylinder when the head is off as the piston is going up and down.
with the head on and the piston is at TDC there is very little room so very little air. When the piston drops it makes more room so the air has to move into the space to fill it to balance the pressure.The faster the piston drops the faster the air is trying to move into the cylinder.
Air is something. It has volume although you can't see it it is there. Unless your in Los Angeles then you can see it.

[Cobra Dude]

The real answer is #2 and here's why -- the piston coming down creates a lower-pressure area in the chamber and the relatively higher pressure air from the intake *flows*E into the lower pressure area. The lower pressure area is called "suction". Technically, atmospheric pressure is pushing the air in, but that definition is already included in the definition of suction, and there is also the lower pressure area in the chamber sucking the air in.

Even for supercharged cars, I don't even believe #3 to be correct because the pressure is no longer atmospheric, but compressed atmospheric.

Cheers,
-Neil.

... Unless your in Los Angeles then you can see it.

[Bob In Ct]

All of you who believe it's suction probably believe that with a strong enough pump a fire truck can suck water up to a bridge 50 feet above the water. Of course the real firemen in the group as well as every physicist on earth know that we can only pull the water up a maximum of 34 feet (after that it boils in the pipe, which is why well water is pushed out of the well by a pump at the bottom). At that point the weight of the atmosphere is equal to the weight of the water.

If I open the door to the dark room will all of the dark get out?

Bob

[PatBuckley]

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