What is the principle of a cylinder pressure gauge?
2 Answers
The principle of a cylinder pressure gauge: When gas pressure enters the curved tube, the tube straightens, thereby driving the pointer on the dial through a lever and gear mechanism to indicate the gas pressure level. A cylinder pressure gauge is a specialized gas pressure gauge, typically composed of a pressure gauge head, tube, one-way valve, and connector. The pressure gauge head is mostly of the Bourdon tube type, with its driving element being a flat tube bent into a circular shape—one end is fixed, and the other is movable. Reasons for high cylinder compression pressure: 1. Excessive oil entering due to carbon deposits; 2. Overly rich air-fuel mixture causing the engine temperature to be too low; 3. Incomplete combustion over a long period and poor exhaust flow.
When it comes to the principle of a cylinder compression tester, I believe the key lies in how it measures the engine's compression force. I've used it quite a few times myself. The basic idea is to connect the gauge to the spark plug hole of the cylinder. When the engine rotates, the piston pushes air upward, and the pressure generated during the compression stroke is transmitted through a tube to the gauge's sensor. The sensor here is usually mechanical, such as an air chamber or spring, which moves the needle to display the pressure value—somewhat like using a blood pressure monitor to measure pressure. The principle is simple but very practical, mainly used to check if the compression ratio is normal. If the pressure is too low, it might indicate air leakage or worn piston rings. For specific usage, you need to remove the spark plug first, connect the gauge, and then start the engine or manually turn the crankshaft a few times. I recommend doing the test when the engine is warm for more accurate results, as a cold engine tends to show lower pressure. This tool is particularly useful for diagnosing engine misfires or weak acceleration. Remember, standard pressure values vary by vehicle, typically ranging between 130 to 180 psi for small cars. If the pressure is unstable, check the valve seals or cylinder wear immediately to prevent minor issues from escalating. In short, the principle is all about making the engine's compression force visible.
