Home
Back
Cranking Pressure Formula:
| From: | To: |
Cranking pressure is the pressure generated in an engine cylinder during the compression stroke when the engine is being cranked (turned over) but not running. It's a key indicator of engine mechanical health and compression efficiency.
The calculator uses the cranking pressure formula:
Where:
Explanation: This formula provides an estimate of the maximum pressure that should be achieved in the cylinder during cranking, based on the engine's compression ratio and current atmospheric conditions.
Details: Calculating cranking pressure helps diagnose engine problems, verify compression ratio modifications, and assess overall engine health. Significant deviations from expected values may indicate issues with valves, rings, or other engine components.
Tips: Enter the engine's compression ratio (typically between 8:1 and 12:1 for most engines) and the current atmospheric pressure. For accurate results, use actual measured atmospheric pressure rather than standard sea level pressure (14.7 psi).
Q1: Why is my actual measured pressure different from the calculated value?
A: Actual pressure may vary due to factors like valve timing, camshaft profile, temperature, altitude, and engine mechanical condition.
Q2: What is a typical compression ratio for engines?
A: Most gasoline engines have compression ratios between 8:1 and 12:1, while diesel engines typically range from 14:1 to 25:1.
Q3: How does altitude affect cranking pressure?
A: Higher altitudes have lower atmospheric pressure, which results in lower cranking pressure for the same compression ratio.
Q4: When should I be concerned about cranking pressure readings?
A: Significant variations between cylinders (more than 10-15%) or readings substantially lower than expected may indicate engine problems.
Q5: Can this calculation be used for both gasoline and diesel engines?
A: While the basic principle applies to both, diesel engines typically have much higher compression ratios and therefore higher cranking pressures.