How does an engine “suck” in air? Like during the intake stroke it goes down which creates a low pressure area and the air rushes in. But how does all that work? How does the piston going down allow air to be pulled in? LOL please explain it as simple TY!
In: Engineering
At the same time the piston goes down, the intake valve opens, allowing air into the cylinder. The opening and closing of the valves are controlled by the camshaft, which is synchronized to the rest of the engine by a belt or chain.
So, as the piston is on the downstroke, the inlet valve is open and draws air/fuel into the combustion chamber. This lowers the pressure in the airbox, inlet and drawers fresh air in to replace it.
Hope this makes sense.
“Sucking” is just what nature does – when there’s a low pressure area, air rushes into it, assuming it can.
Grab a big plastic bottle.. the bigger, the better, but it needs to be some thing you can squeeze it a bit, and it’ll return to its original shape after you let go. With the lid off, squeeze it a few times. When you squeeze it blows air out, but when you let go it sucks air in. Same thing in the car engine. This is even how humans breathe air.
The engine’s intake valve opens, allowing a path for air from the intake into the cylinder’s space. The piston inside the cylinder then moves downwards, meaning the amount of open space inside the cylinder effectively grows. More space becoming available sucks in air through the valve. This sucks in air. When the piston is at the top, the plastic bottle is squeezed. When it’s at the bottom, the plastic bottle is in its normal shape. And the valves are 2 lids on the cylinder, one from the intake and where fuel also comes in, and one out to the exhaust at the back of the car.
> How does the piston going down allow air to be pulled in?
Air near the surface of Earth is under pressure due to the weight of all the air above it being pulled down by gravity. This means that if space opens up it is pushed in by that pressure.
Think about if you have a big tub of water and open up a bottle full of air at the bottom of the tub. The air will be pushed out and replaced by water, right? This basic idea works for air as well except in this case there is *nothing* filling that space the piston opens up.
Think of a syringe. As you increase the volume on the inside, more air will go into it through the opening.
In an engine, the opening is the intake valve. It opens and the piston begins to pull away, causing air to rush into it. Then the intake valve closes, fuel is added, and the piston compresses and ignites.
There are other methods too.
Turbochargers use the exhaust flow to spin a fan that actually sucks in and forces air into the intake. More air means more fuel and more power.
Superchargers are very similar, but instead of using exhaust gas, it uses a belt.
Take a syringe, put it against your finger and pull the plunger. Do you feel that pressure? It’s exactly like that.
Engineering terms PV=nRT, as V goes up P goes down and air moves from higher P to lower P.
The cylinder and piston are precisely machined so along with the lubricants it creates pretty much an airtight chamber. So after the exhaust gases are expelled on the upstroke the valve opens to allow fresh air in and the piston pulls the air in on the downstroke since it creates a vacuum in the cylinder
The same way you suck air into your body. Breath in your chest gets bigger, your chest expands, this means that you have the same mass of air filling a larger volume. That reduces the pressure and the air outside will flow in to make it the same.
Air enters the intake and then runs through the air box, which houses your air filter. The filtered air runs through your throttle body, which has a throttle plate that opens as you press the accelerator.
After the throttle body, the air flows into the intake manifold, which directs the air to the intake valves for each cylinder.
As each piston begins an intake stroke, the valve opens. The piston acts like the plunger in a syringe, drawing the air through the intake system into the cylinder.
– The cylinder is full of piston.
– The intake valve opens and the piston is pulled to the bottom of the cylinder which fills in with air just like a syringe.
– The valve closes trapping the air, the piston raises thus compressing the air, gas is squirted in via the injector and the spark plug makes it go bang forcing the piston to the bottom of the cylinder.
– The exhaust valve opens as the piston rises pushing the combustion products out the muffler.
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