2 Answers

HI

The compression ratio is a single number that can be used to predict the performance of any internal-combustion engine. Basically its the volume of the cylinder at full intake to the volume at full compression.
The ratio is calculated by the following formula:

, where
b = cylinder bore (diameter)
s = piston stroke length
Vc = volume of the combustion chamber (including head gasket). This is the minimum volume of the space into which the fuel and air is compressed prior to ignition. Because of the complex shape of this space, it usually is measured directly rather than calculated.
Due to pinging (detonation), the CR in a gasoline/petrol or LPG or CNG-powered engine will usually not be much higher than 10:1.
In engines with a ping sensor and an electronic control unit, the CR can be as high as 12.5:1 (2005 Audi A6 3.2)
In a turbo charged or super charged engine the CR will be around 8.5:1
In a diesel engine the CR will be 20:1 and higher.

I HOPE THIS EXPLAINS  CR OK FOR YOU IF YOU WANT FURTHER INFO LOG ONTO GOOGLE  SEARCH ENGINE AND ASK YOUR QUESTION THERE WILL BE THOUSANDS OF SITES EXPLAINING IT IN MORE DETAIL

HOPE THIS HELPS

MONDEOMAN

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