I’ve always hear it when i’m watching about racing cars, i’m a farn of cars but i dont know about naturally aspirated and supercharged engines.
In: Other
A naturally aspirated engine is one that only relies on the movement of the pistons to pull in air. Because of this, the amount of air (and therefore fuel, and therefore power) that can enter the engine is capped at the displacement of the engine. A supercharged or turbocharged engine uses a high speed pump to force more air into the engine. More air = more fuel = more power.
Naturally aspirated engines are the simplest ones. The engine draws air straight from the atmosphere. It then gets mixed with fuel, compressed and ignited. One of the limiting factor in an engine is how much air it can draw inn. The more air the more fuel and the bigger the explosion. But a naturally aspirated engine can only fill the cylinder. So a 0.5L cylinder can only get 0.5L of atmospheric pressure air each intake stroke.
Boosted engines however fixes this problem. By compressing the air from the atmosphere you can fit more air into the same space. So you might push 1L of air into the 0.5L cylinder. Now you have twice the amount of air, twice the amount of fuel and twice the power, in theory. There are mainly two types of ways to boost the engine. The first is a supercharger. It is driven by the engine, typically through a belt, and compress the intake air. The issue with a supercharger is that it takes power to run it. So you do not get out all the extra power you put into the engine. The second way to boost an engine is with a turbocharger. It is driven by the exhaust and not the engine. So you get a lot more of the added power. The problems with a turbo is that the speed of the exhaust or even the speed of the turbine does not correspond to the speed of the engine. So you get turbo lag and you might max out the turbo speed, etc.
Another important thing about boosted engines is that when you compress air it gets hotter. And hotter air have higher pressure and lower density. So just compressing it does not necessarily increase the density as much which is what you want. So most boosted cars come with an intercooler which cools down the supercharged air making it more dense.
Ok, so in order to function an engine needs air to mix with the fuel. With a naturally aspirated engine, air is drawn in through an intake, with a supercharged engine the super charger forces more air in, which in turn produces more power. Same with a turbo, the difference is how they are run. A supercharger is mechanically powered, while a turbocharger is powered by the exhaust gases.
So there are two types of engine intake systems – naturally aspirated and “forced” aspirated. There are two subtypes of forced aspiration – supercharged and turbocharged engines.
All engines require air to function – “they need to aspirate,” which basically just means “take air in.” In a naturally aspirated engine, there is no mechanism that forces air into the engine, it’s all just physics of the combustion reaction itself, atmospheric pressure and the working of the engine. The engine takes in air in its own to compensate for pressure changes that happen as the engine operates normally.
Now, in an engine with forced aspiration, this is not what is happening. With forced aspiration, there is a mechanism attached to the air intake of the engine that artificially increases the pressure of air going into the engine. The intake mechanism essentially is forcing air into the engine, instead of relying on atmospheric pressure and engine combustion alone. There are two types of mechanisms used – superchargers and turbochargers. Both of them are basically specialized (often nautilus-shaped in cars) tube systems that attach to the air intake and force air into them. They’re basically air compressors.
With a supercharger, the air compressor is essentially driven by the engine itself, meaning some spare engine power runs the compressor to increase the intake pressure. The supercharger itself is normally connected to the crankshaft by means of a belt system. The supercharger’s power – and thus its compression strength – is also fixed in strength, depending upon engine power, meaning the harder the engine is working/the more power it’s putting out, the harder the supercharger works. More power from the engine, more power to the supercharger, and so on.
A turbocharger is very similar mechanically to a supercharger – a mechanism is attached to the intake that forces air into the engine. However, whereas a supercharger is connected to the engine by means of a belt, and thus its compressive power increases as engine power increases in a linear fashion, a supercharger is powered by engine exhaust gases instead. Instead of their being a belt or gear system connecting the intake mechanism to the rngine, engine exhaust is pushing the intake mechanism to drive it. In this way, a turbocharger also increases motor power non-linearly – the harder the turbo works, the more compressed the intake air is, which means that the exhaust gases are pushed out at higher pressure, increasing the strength of the compressor. This turns into a feedback loop as engine operation increases, thus increasing exhaust gas pressure, and around it goes. Because of how a turbocharger works, it provides more power to the engine the harder the engine is working, which differs from a supercharger. This is why you can drive a car with a turbo “under the turbo” – a you’re not running the engine hard enough at low RPMs or during normal driving to increase exhaust gas pressure enough to drive the turbo hard enough to increase power. A supercharger can’t do that – for any given engine output, the supercharger provides a fixed amount of additional compression.
Turbochargers and superchargers are used on cars to increase engine power and efficiency. However, on planes they’re used to allow them to fly at high altitudes where the atmospheric pressure is not high enough and the air is thin enough that the engine can’t get enough oxygen to work. Using a super or turbocharger increases the amount of oxygen and pressure, allowing the engine to function normally.
A simple analogy: If you open your window, that is the same as naturally aspirated. If you place a fan in that open window to blow in more air from outside, that is supercharged.
A car engine mixes gas, oxygen, and spark to create combustion. The air and fuel is mixed in the cylinder and when it explodes it expands, powering the engine. The bigger the explosion, more power. So a bigger engine makes more power than a smaller engine. Also, the more explosions you have, the more power (hence v6, v8, v10, etc).
The ideal ratio of gas and oxygen is 14.7 units of air to 1 unit of fuel. This produces the most efficient combustion and thus the most power. A naturally aspirated engine just draws in air from outside the car, and then adds enough units of fuel to get to that ideal ratio.
Let’s do a simple illustration. Imagine you are holding an empty jar. To make it simple, let’s say it is exactly the correct size to hold 147 air molecules. You take the lid off and let it fill with air, then close the lid. The jar will have 147 air molecules in it. To get the ideal combustion you would have to add 10 fuel molecules. This is how a naturally aspirated engine works. But the power is limited here, you will have a small explosion with only 147 air molecules. If you want a bigger explosion, you need to be able to hold more air molecules. One way is to use a bigger jar. Another way is to get several jars together.
But wait! There is another way. You may recall that air can be compressed. We can actually squeeze more air molecules into the jar. If you pump more air into the jar, now you can fit more molecules of air in there, and then you can pump more molecules of fuel, and get a bigger explosion. That is basically what a turbo or supercharger is, it’s a turbine that pumps more air into the cylinder to get more combustion out of the cylinder, compared to regular non-compressed air that is just hanging outside the car.
Knowing this, we can also understand how altitude affects engine performance, and also how cold air intakes work. The higher you go, the air is less dense, meaning there are less air molecules in a given space. So combustion engines produce less power at higher altitudes. Cold air intakes work off the fact that cold air is more dense than hot air. Since engines produce a lot of heat, they heat up the air near them, so moving the air intake away from the engine will benefit this. However, this is such a small difference that you probably aren’t going to notice it.
An internal combustion engine is basically an air pump, it sucks air in and we mix that with fuel and the two combined is how we get the fire to drive the engine.
A naturally aspirated engine is just pumping the air by itself with its pistons- every time the piston goes “down” and the valve opens it sucks in air, just like your lungs. The air is at normal atmospheric pressure
A supercharger is a separate air compressor which is driven by the engine, which means that when the air reaches the engine, it’s under more pressure than normal air. It still breathes in almost the same but there is more air in each breath.
(A turbocharger also adds a separate air compressor which is driven by the exhaust gas instead of the engine, and pushes in more air, it’s a different method but the same idea, squishing the air means each gulp has more air in it.)
(nitrous is similar but instead of compressing the air so you get more per gulp, it changes the mixture of the air so there’s more oxygen per gulp. Like putting more whisky in your drink, rather than drinking more whisky-and-coke)
More air means more fuel means bigger kabooms
Latest Answers