The compression ratio of an engine is responsible for its performance. Basically, it is the relationship that exists between the volumes of the combustion chamber measured when the piston is at its maximum and minimum stroke. When the intake and exhaust valves are closed and the piston moves, the air and fuel mixture cannot escape and is compressed. The compression ratio is the change in the volume of the cylinder during this process and is determined by 5 factors: the change in the volume of the cylinder, the volume of the combustion chamber, the volume of the piston head, the head gasket and the residual volume when the piston is at top dead center. To calculate the compression ratio of your vehicle, use this formula: compression ratio = volume at minimum compression divided by volume at maximum compression. It's not as easy as it sounds, but it can be done with a little commitment.
Steps
Step 1. Find and keep the owner's manual of your vehicle at hand, necessary to know the measurements of some parts of the engine
Step 2. Clean the engine as much as possible (you can find special additives on the market) before starting to work on it
Step 3. Measure the inside diameter (also called caliper) of the cylinder, ie the bore
To measure it you need to use an instrument also called a caliper.
Step 4. Measure the distance between the two positions of minimum and maximum piston travel (called top dead center and bottom dead center)
This distance is called the piston stroke.
Step 5. Look for the volume of the combustion chamber in the manual
Step 6. Look for the compression height value in the manual
Step 7. Look for the volume of the piston head in the manual
Step 8. Calculate the residual volume at piston travel at top dead center (gauge x gauge x 3, 14 x distance between piston and cylinder end stop)
Step 9. Measure the thickness and gauge of the head gasket
Step 10. Once you have gathered all this information, use this formula to calculate the compression ratio:
cylinder volume + residual volume at maximum piston travel + piston volume + seal volume + combustion chamber volume, all divided by residual volume at maximum piston travel + piston volume + seal volume + chamber volume a outbreak.
Step 11. If your user's manual provides inches, convert them to centimeters and millimeters
Advice
There are many internet sites that directly calculate the compression ratio: just enter the required data and that's it
Warnings
- Be careful when working on a car engine. Check that it is cold before touching it and wear protective gear such as gloves, goggles, closed shoes.
- Make sure you have the right tools to take the measurements described. If you use unsuitable tools, you could harm yourself or others.
