# Piston Deck Volume

on . Posted in Fluid Dynamics

Piston deck volume, abbreviated as PDV, refers to the volume of the combustion chamber that is created by the space between the top of the piston and the cylinder head when the piston is at top dead center (TDC).  It is an important factor in determining engine compression ratio and combustion efficiency.  The piston deck volume can be calculated by measuring the distance between the top of the piston and the deck surface of the engine block or cylinder head when the piston is at TDC, and then calculating the volume of this space using the formula for the volume of a cylinder.

To calculate the piston deck volume, you would measure the distance between the top of the piston and the deck surface at TDC, and then use this measurement as the height in the formula above.  The radius is equal to half the diameter of the cylinder, which is usually a known quantity based on the engine's specifications.  The piston deck volume can be adjusted by machining the piston crown or cylinder head to change the distance between the piston and the head at TDC.  This can be used to optimize engine performance for specific applications by adjusting the compression ratio and combustion efficiency.

## Piston Deck Volume Formula

$$\large{ PVD = \left( 0.7854 \; BORE^2 \; DPD \right) + \left( VPD - VPB \right) }$$
Symbol English Metric
$$\large{ PDV }$$ = piston deck volume  $$in^3$$  $$cc^3$$
$$\large{ BORE }$$ = bore $$in^3$$ $$cc^3$$
$$\large{ DPD }$$ = deck of piston distance $$in$$ $$mm$$
$$\large{ VPD }$$ = volume of piston depressions $$in^3$$ $$cc^3$$
$$\large{ VPB }$$ = volume of piston bumps $$in^3$$ $$cc^3$$

Tags: Engine Equations