How to Calculate Car Engine Compression Ratio

We often wonder if our vehicle is in good shape, and if it can survive in the long journey and everything we use for everyday. In addition to getting a basic car service and choosing to have recommended services according to mileage, there is an easy way to check the state of our machine, so at OneHowTo, we show you how to calculate your machine’s compression ratio effectively.

1.For this you will need a pressure gauge to measure the engine’s compression. You can buy thisin shops specializing in car parts and accessories or on the Internet.

2. Start the car and let the engine run until it reaches its normal temperature. You shouldn’t carry out this check on a cold engine, so it is best to do it after having driven a short distance.

3. Switch off the ignition and once the car is off, disconnect the wires located in the spark plugs, always focusing on what you’re doing because later you will have to reconnect them in the same positions. To avoid any uncertainty, you can take a picture of the spark plugs before disconnecting the cables.

4. Unscrew a spark plug and place the tip of the gauge in the hole where the spark plug is inserted. It is very important that the gauge’s nozzle is fully inserted inside this hole.

5. Now you have to ask someone else to start the engine and speed up the car for about four seconds, in this way you can measure the compression of the spark plug engine. Turn off the engine and repeat the above steps with each of your car spark plugs.

6. Each spark plug should have the same pressure, and it is important that they match the pressure recommended by the car manufacturer in the handbook. If you have a petrol engine the difference between cylinders can be up to 1.5 bar, which is completely normal.

7. If you don’t know the manufacturer’s guidelines regarding the suitable compression for your car’s engine, then rely on the compression ratio of your engine (whether petrol or diesel) and add up those numbers. For example in a compression ratio of 14:1 the sum result is 14+1, so 15 should be the pressure value as indicated on the manometer.

8. If there is a problem with the compression of your car engine, it is best to take him to check the service to determine the source of the leak and allow the professional to fix it.