Compression Ratio Calculator
The Compression Ratio Calculator determines an engine's compression ratio from swept volume (displacement) and clearance volume (combustion chamber). Optimize your engine build for power, efficiency, and fuel octane requirements.
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What is Compression Ratio?
Compression ratio is the ratio of the total cylinder volume (when the piston is at bottom dead center) to the clearance volume (when the piston is at top dead center). A 10:1 compression ratio means the air-fuel mixture is compressed to 1/10th of its original volume before ignition.
Higher compression ratios increase thermal efficiency and power output but require higher octane fuel to prevent detonation (knock). Stock gasoline engines typically run 9:1 to 12:1. Diesel engines use 14:1 to 25:1 because diesel fuel ignites through compression alone.
적용 수학 공식 및 방정식
이 Compression Ratio Calculator는 5가지 핵심 수학 공식을 사용합니다:
1 Compression Ratio ▼
A cylinder with 500cc swept volume and 55cc clearance: CR = (500 + 55) / 55 = 10.09:1.
2 Swept Volume (Single Cylinder) ▼
Bore = 86mm, Stroke = 86mm: V = 0.7854 × 86² × 86 = 499.6 cc.
3 Clearance Volume from CR ▼
To achieve 9.5:1 with 500cc displacement: CV = 500 / (9.5 - 1) = 58.82 cc.
비율 계산기 사용법
이 비율 계산기는 아래의 3단계로 쉽게 사용할 수 있습니다:
수치 입력하기
입력 칸에 알고 있는 비율 값을 입력합니다. 구하려는 미지수 자리의 칸 하나는 비워둡니다.
모드 선택하기
비율 모드(풀기, 간소화, 스케일링)를 선택합니다. 각 모드는 입력한 수치에 맞춰 다른 공식들을 적용합니다.
결과 확인하기
계산하기 버튼을 누릅니다. 결과 화면에 정답과 함께 시각적인 비율 바, 원형 차트, 상세한 단계별 풀이 과정이 출력됩니다.
실제 예제 문제 및 단계별 풀이
비율 계산기를 활용하여 아래 3가지 예제 문제를 단계별로 해결하는 과정입니다:
입력 1 Engine with 600cc displacement and 60cc chamber
입력 2 Calculate displacement for 88mm bore, 82mm stroke
입력 3 Find clearance volume for 12:1 CR, 450cc displacement
자주 묻는 질문 (FAQ)
What compression ratio is best for pump gas (87 octane)? ▼
For 87 octane regular gas, stay at or below 9.5:1 static compression ratio. Modern engines with direct injection and variable valve timing can safely run 10:1 to 11:1 on regular fuel.
How does compression ratio affect horsepower? ▼
Each 1-point increase in compression ratio typically yields 3-4% more power, up to a limit. Going from 9:1 to 10:1 might add 10-15 HP on a 300 HP engine. Beyond about 13:1, gains diminish and knock risk increases.
What is the compression ratio of a diesel engine? ▼
Diesel engines run 14:1 to 25:1 compression ratios. The high compression heats air enough to ignite diesel fuel without spark plugs. Modern common-rail diesels typically use 16:1 to 18:1.
How do I measure clearance volume? ▼
Fill the combustion chamber with fluid (isopropyl alcohol or light oil) through a burette with the valves closed and piston at TDC. The volume of fluid needed equals the clearance volume. Typical values range from 40-70cc.
Does milling the head increase compression ratio? ▼
Yes. Milling (shaving) the cylinder head reduces clearance volume, increasing compression ratio. Removing 0.020 inches from the head surface typically raises CR by 0.3-0.5 points depending on chamber size.