L&M Newsletter

Piston Velocity Calculator

Piston velocity is a critical component of engine performance and expected durability. High piston velocity promotes performance when linked to the proper intake/exhaust tract and valve timing. When the piston applies force to the air it translates energy into cylinder filling and if the energy is high enough we can expect the cylinder to overfill causing effect VE to be over 100%.

Piston velocity is also used in the calculation of ā€œgā€ loading of the reciprocating pats and the required strength of these components needed for high velocity operation. Current technologies in the rods, bolts, and crankshafts have made dramatic increases in component strength allowing them to operating higher velocities when compared to older manufacturing processes. Furthermore, increased availability has made these technologies available to masses and not just a select few of elite engine builders.

The calculator allows one to investigate rod/stroke ratio and piston velocity changes around TDC. Further calculations will allow you to calculate features such as theoretical max inlet demand.

The calculator also computes the distance the piston is from TDC per crank degree and is useful for many further calculations such as expected valve to piston clearance.

Piston velocity is in feet per minute, rod angle to bore is calculated in degrees, and crankshaft angular velocity is in radians/minute computed from max RPM input.

Inputs

  • Bore - Bore diameter in inches
  • Stroke - Stroke length in inches
  • Rod Length - Rod length in inches
  • RPM - Engine rotation speed in revolutions per minute

Outputs

  • Crank Angle (°) - Crank angle in degrees
  • Piston V (fpm) - Piston velocity in feet per minute
  • Rod Angle (°) - Rod angle in degrees
  • Depth Below TDC (In.) - Distance between the top of the piston and top dead center in inches
  • Crank Angle (rad) - Crank angle in radians
  • Rod Angle (rad) - Rod angle in radians

Bore Stroke Rod Length RPM

  

Crank Angle (°) Piston V (fpm) Rod Angle (°) Depth Below TDC (In.) Crank Angle (rad) Rod Angle (rad)