엔진오일 교환 수리 사례

2026. 6. 30. 작업

난이도 & 준비물

증상

Static vs. Effective compression: Why does higher effective compression not require higher octane gas?

처리 내용

tl;dr: They do. It's just harder to tell how much. The longer answer is that they do and that effective compression is failing you as an approximation for actual effects. Think about detonation (AKA premature ignition of the fuel-air mixture). Normally we consider two causes: compression (the change in the space enclosed by the cylinder as the piston moves up and down) and temperature (e.g., measured temperature of the intake air). In reality, there is only temperature. Let's back all the way to the ideal gas law : PV = nRT where P is pressure, V is volume and T is temperature (in degrees Kelvin, remember!) and the rest are interesting constants that aren't germane to this discussion. Compression causes that V value to decrease and P to increase. In an ideal world, that would be the end of it: the compression of the cylinder would be a 100% efficient process without temperature increase. Unfortunately, we live in an actual rather than an ideal world. The best simple model for what's ha