The resulting pressure P2 is called the dynamic compression is affected by engine speed, camshaft lobe profile, piston rings sealing, valve seats sealing, air density, etc. And if it did have both modes of forced induction, the cooler immediately upstream of the intake manifold is still called the aftercooler. So unless the engine is running a supercharger and a turbocharger, it has no intercooler. The latter implies that there is a second stage of compression on the engine. BTW, the proper term from an engineering point of view is aftercooler, not intercooler. My own opinion is that any forced induction engine should have an aftercooler. Heat of compression is excluded for two reasons - inlet temperature does not have as significant affect on stresses imposed onto the rotating elements of the engine as boost does and an aftercooler will negate the heat of compression. In simplified form, an equation can be presented as P1 x V1 = P2 x V2, where P1 is the intake manifold pressure, P2 is static combustion chamber pressure (more on this in a sec) and the ratio of V1 to V2 is the piston’s compression ratio. "We’ve all wondered it before - how much boost can the NSX engine withstand, while at the same time, not imbedding the crankshaft into the pavement? Perhaps this may shed some light onto the subject, based on thermodynamic gas laws. More evaporation is a sign of higher thermal efficiency, meaning the engine performs better without using too much extra energy to gain this power." The tight packing of the air-fuel mixture helps both air and fuel to blend better and when the explosion occurs more of the mixture evaporates. High compression ratios cause more power by compressing the air and fuel even tighter than average and thus creating a more forceful explosion. Cars using gas with a higher octane rating or a knocking sensor can use higher compression ratios, but still cannot match the high ratio of a diesel engine." A loud knocking noise results and, if not fixed, continuous engine knocking can permanently damage the engine. This occurs when a larger explosion than desired occurs and causes the piston to move upward or downward too quickly. The disadvantage of a higher compression ratio in a gas engine is the possibility of engine knocking or pinging. A ratio of 13:1 is considered high in a gas engine while a diesel engine can range from 14:1 up to 23:1 depending on the type. Diesel engines, on the other hand, are designed for high compression in order to function. High compression ratios in gas engines often cause a problem known as engine knocking. The amount of air-fuel mixture does not change, but rather is simply pressed into a significantly smaller space to create a large explosion.ĭiesel engines use compression to create power while gas engines use a spark to ignite the air-fuel mixture that creates the necessary power to drive the vehicle forward. A ratio such as 13:1, for example, means that the engine holds 13 times more volume when the piston is down than when it is compressed. After finding the volume of the cylinder when the piston is down, and therefore not compressed yet, the engineer would then need to calculate the volume when the piston is up and the air-fuel mixture has been compressed. During one stroke of the engine, the piston moves from the bottom up toward the top and compresses the air-fuel mixture. To calculate the compression ratio of an engine, an engineer would first calculate the volume a cylinder in the engine can hold when the piston is at the bottom of the cylinder. Engines with higher compression ratios are generally considered better because they create more power while still maintaining efficiency. Diesel- and gas-powered engines alike each have a compression ratio, though the design of the diesel engine encourages a higher compression ratio. This ratio applies to both internal combustion engines, such as those found in modern-day vehicles, and seldom-used external combustion engines. Before you get into the NSXPrime article, make sure you know what compression ratio is or else this whole read goes to waste.Ĭompression ratio refers to the volume, or amount, of an air and fuel mixture that the combustion chamber in a combustion engine can hold when it is empty and at its largest size compared to the volume it holds when the mixture is compressed down to the smallest size possible. I hear this from a lot of people, "Damn he's running 30lbs of boost! That is so sick!" What I never hear people say is, "Damn he's running 30lbs of boost but his compression ratio is only 6.3:1." Compression ratio is just as important if not more important then boost. It's also from NSXPrime (damned good forum!). Again, I've found an awesome read that I just had to share with everyone.
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