What is the normal cylinder pressure for a car?
2 Answers
Car cylinder normal pressure values vary depending on different conditions: 1. For gasoline engines, the normal cylinder pressure ranges between 8 to 11 bar; 2. For diesel engines, the normal cylinder pressure ranges between 12 to 16 bar. The cylinder is composed of cylinder barrel, end cover, piston, piston rod, and sealing elements, and its function is to separate the turbine's flow path from the atmosphere, ensuring that steam completes the work process within the turbine. The method to check cylinder pressure is: 1. Install the cylinder pressure gauge on the engine; 2. Warm up the car, run the engine to normal operating temperature, maintaining coolant temperature around 90 degrees; 3. Remove all spark plugs or fuel injectors from the car; 4. Press the accelerator to fully open the throttle; 5. Screw the threaded connector into the spark plug hole; 6. Start the engine for two seconds, read the pressure value after the pointer stabilizes, press the one-way valve button to release pressure, allowing the pointer to reset.
When it comes to cylinder pressure in cars, based on my years of experience working with vehicles, gasoline engines typically should be within the range of 120 to 180 pounds per square inch to be considered normal, depending on the model and compression ratio. Diesel engines have higher pressure, generally around 300 to 600. High-compression sports cars might approach the upper limit, while regular family cars are ideal around 150. Measurement requires a professional pressure gauge connected to the spark plug hole while slowly turning the engine. If the pressure is too low, it could be due to piston ring or cylinder wall wear causing air leakage, leading to hard starts or black smoke from the engine. Excessive pressure is rare but can damage valves. In hot weather or at high altitudes, pressure may slightly decrease, so environmental factors should be considered during checks. Regularly testing the pressure can help prevent major overhauls—for example, I perform a simple pressure test during my car's annual maintenance.
