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Knowledge Dynamic Compression Ratio

Dynamic Compression Ratio (DCR) is an important concept to create a high-performance machine. Specifies the compression ratio is calculated after the intake valve closes that will inform you about octane fuel will be used.

The compression ratio (CR) of the engine is the cylinder volume ratio compared with the volume of the combustion chamber. A cylinder with 10 units of volume and the volume of the combustion chamber 1 has a compression ratio of 10: 1. Static Compression Ratio (SCR) is the ratio of the most frequently cited. It is derived from the volume of the cylinder using a crank full stroke (BDC to TDC). More dynamic compression ratio using a piston position at the intake valve closing after BDC to determine the volume of the cylinder pressure.

Dynamic Compression Ratio


The difference between the two is huge. For example, with a cam that closes the intake valve at 70ยบ after TDC, the piston has been increased by 23 mm of TDC at the point of closing the valve. This reduces the pressure cylinder. This is the only difference between the SCR and DCR count.
  • Calculations used in calculating the CR is the same.
  • DCR is always lower than the SCR.
Not to be confused also the dynamic compression ratio with pressure cylinder. Pressure cylinder is almost constantly changing. It occurs due to many factors including RPM, design intake manifold, cylinder head and efficiency, the design of the exhaust, valve timing, throttle position, and a number of other factors. DCR measured or calculated from the actual dimensions of the machine. Therefore, unless the variable cam timing is used, such as static compression ratio, dynamic compression ratio calculated fixed when the machine was built and never changed during operation of the machine.

Two important points to remember:
  1. DCR is always lower than the SCR
  2. The DCR is not changed at any time during the operation of the machine
Hope useful, thanks for read article from Electronic And Mechanic.

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