Engine

                    Power                  
       
     
  Brake Mean Effective Pressure   Volumetric Flow Rate  
       
           
  Indicated Mean Effective Pressure   Friction Mean Effective Pressure  
           
           
Compression/Expansion Ratio   Combustion   Pumping Losses   Mean Piston Speed   Total Bore Area   Volumetric Efficiency
     
     
  Gas Dynamics  

For a reciprocating engine, the total bore area (Ab) is the area of one cylinder bore times the number of cylinders (N):

Ab = N
π
4
D 2
(1)

Where D is the cylinder bore diameter. Although, «cylinders» are not necessarely round (like the oval piston shown in the next figure).

oval piston