Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

# Piston Engines - Compression Ratios

## Cylinder volume and compression ratios in piston engines.

The static compression ratio in a piston engine is the ratio between the volume of the combustion chamber when the piston in the cylinder is at the bottom of its stroke and the volume of the combustion chamber when the piston is at the top of its stroke. It can be expressed as

CR = (Vd + Vc) / Vc

= (π d2 s / 4 + Vc) / Vc            (1)

where

CR = compression ratio

Vd = piston displacement volume - total volume swept by the piston (cm3, in3)

Vc = clearence volume - volume left in the cylinder when the pistion is at the top dead center (cm3, in3)

d = piston diameter (cm, in)

s = piston stroke (cm, in)

## Related Topics

• ### Miscellaneous

Engineering related topics like Beaufort Wind Scale, CE-marking, drawing standards and more.

## Related Documents

• ### 12 Volt - Electric Automotive Wiring

Maximum wire lengths vs. currents in the 12 volt electrical system of a car.
• ### 12 Volt - Maximum Wire Length vs. Current

Maximum length of copper wire with 2% voltage drop.
• ### Acceleration Units Converter

Converting between units of acceleration.
• ### Average Velocity

Distance traveled vs. time used.
• ### Car - Required Power and Torque

Power, torque, efficiency and wheel force acting on a car.
• ### Car - Traction Force

Adhesion and tractive force between car wheel and surface.
• ### Car Acceleration

Car acceleration calculator.
• ### Car Fuel Consumption - liter/100 km

Calculate fuel consumption in liter per km - consumption chart and calculator.
• ### Cars - New vs. Old Car Cost Calculator

Calculate and compare the costs between owning a new vs. an old car.
• ### Centripetal and Centrifugal Acceleration Force

Forces due to circular motion and centripetal / centrifugal acceleration.
• ### CO2 Calculator - Emissions from Cars

Calculator for CO2 emissions from different kind of cars (gasoline, diesel, LPG, electrical), comparing with alternative forms of transportation (as airplane, bus and train).
• ### Compressed Air vs. Free Air - Compression Ratio

The ratio of compressed air pressure to free air pressure.
• ### Drag Coefficient

The drag coefficient quantifies the drag or resistance of an object in a fluid environment.
• ### Electrical Vehicle Charging - Power vs. Voltage and Amps

EV Charging - AC vs. DC, single phase vs. three phase and power vs. voltage and amps.
• ### Ethylene Glycol Heat-Transfer Fluid Properties

Properties like freezing point, viscosity, specific gravity and specific heat of ethylene glycol based heat-transfer fluids, or brines.
• ### Garage Ventilation

Exhaust ventilation from garages and workshops.
• ### Impact Force

Impact forces acting on falling objects hitting the ground, cars crashing and similar cases.
• ### Piston Engines - Displacement

Calculate piston engine displacement.
• ### Reliability of Machine Components

Mean Time Between Failure - MTB and reliability of machine components and systems.
• ### Rolling Resistance

Rolling friction and rolling resistance.
• ### Vehicle - Distance Traveled vs. Velocity and Time (km/h)

Speed (km/h) vs. time (hours) and distance traveled (km).
• ### Vehicles Traffic Flow and Density

Traffic flow and density as used in highway design.

## Search

Search is the most efficient way to navigate the Engineering ToolBox.

## Engineering ToolBox - SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with older versions of the amazing SketchUp Make and the newer "up to date" SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp Make/Pro from the Extension Warehouse !

We don't collect information from our users. More about

We use a third-party to provide monetization technologies for our site. You can review their privacy and cookie policy here.

You can change your privacy settings by clicking the following button: .

## Citation

• The Engineering ToolBox (2020). Piston Engines - Compression Ratios. [online] Available at: https://www.engineeringtoolbox.com/compression-ratio-piston-engine-d_2189.html [Accessed Day Month Year].

Modify the access date according your visit.

6.3.17

.