Definition of compression ratio in English:

compression ratio


  • The ratio of the maximum to minimum volume in the cylinder of an internal combustion engine.

    • ‘A host of engineering revisions to the motor include new pistons, higher compression ratio, higher profile camshaft, new injectors and a less-restrictive titanium exhaust system.’
    • ‘To determine the compression ratio of an internal combustion engine, compare the greatest volume of the piston cylinder (when the piston is at it's maximum excusion) to the lowest volume (when the piston is at top dead centre).’
    • ‘Then, to compensate for the oversize valve reliefs, the piston dome is made taller to produce the advertised compression ratio.’
    • ‘Among the changes are a new ‘thick’ wall composite intake manifold, camshaft profile and valve-train modifications and a raised compression ratio of 9.6: 1.’
    • ‘The Manley connecting rods and pistons swing on a Callies crankshaft and provide a compression ratio of 15 to 1.’
    • ‘As the engine load increases, the head tilts by up to four degrees in order to lower the effective compression ratio by altering the volume of the combustion chamber with the piston at top dead center.’
    • ‘The valve pocket chamber and the pistons are pulled to figure out the compression ratio.’
    • ‘This tilting effectively changes the volume at the top of the combustion chamber, thereby changing the compression ratio.’
    • ‘It also works best with engines using a higher compression ratio, typically 12: 1 against the typical 9.5: 1 found in petrol engines.’
    • ‘Lowering the compression ratio from 10.5 to 9.8: 1 dropped the fuel requirement from premium to regular unleaded.’
    • ‘Raising the compression ratio or supercharging an engine increases cylinder pressure, and it is this which increases the power - not the fuel itself.’
    • ‘The compression ratio was also increased, from 11.0: 1 to 11.1: 1.’
    • ‘The proven turbocharged boxer engine also benefits from sodium-filled exhaust valves and a rise in the compression ratio from 8.0: 1 to 9.0: 1.’
    • ‘This lets us keep the turbo spinning, and run a higher compression ratio than normal for a turbo engine.’
    • ‘The diesel approach of using a high compression ratio was an obvious avenue for investigation but researchers quickly discovered that ratios beyond 12: 1 cause severe knock during full-load operation.’
    • ‘The compression ratio has been lowered to 8: 1 and a special stainless steel exhaust system copes with temperatures up to 960 degrees Celsius.’
    • ‘But he seems confident that ‘with large bore sizes, a piston that has some crown to it and a high compression ratio, dual spark plugs will be a significant advantage’ in meeting exhaust standards.’
    • ‘The double turbochargers are the major change over the 530i, but there is also a lower compression ratio for smoother running and lower emissions of nitrogen oxides when the turbos are not boosting.’
    • ‘Because the mixture is homogenous, the compression ratio can be increased without fear of detonation, and there is no need for a throttle valve in the intake air stream.’
    • ‘FEV showed a 4-cylinder Audi with variable compression ratio at this year's SAE Exposition in Detroit.’


compression ratio

/kəmˈpreSHən ˌrāSH(ē)ō/