crevice volume

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Equation / Last modified by KurtHeckman on 2017/05/23 18:08
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KurtHeckman.crevice volume
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ce097ee9-1c09-11e4-b7aa-bc764e2038f2

The Piston Crevice Volume calculator computes the crevice volume (Volc) of a crevicevolume-illustration.png  Piston Ring Crevice combustion engine cylinder as a function the bore diameter(bD), piston diameter (pD) and the top ring depth (rD).

INSTRUCTIONS: Choose your preferred units, the default is inches and mils, and enter the following:

   Inch Equivalences
FractionDecimalMils
1/16th0.062562.5
1/32th0.0312531.25
1/64th0.01562515.625

Cylinder Crevice Volume: The volume is computed in cubic inches.  However, the can be automatically converted to other volume units (e.g. cubic centimeters aka CCs) via the pull-down menu.

The Math

Engine Math (Baechtel) and I disagree on this equation.  Engine Math takes the difference of the diameters (bore and piston), multiplies that difference by the circumference of the bore to create the surface area of the crevice and then multiplies that surface area by the depth to the top ring to get the volume.  The surface area of that equation is geometrically wrong.  Fortunately these crevice volumes don't affect much.  But the mathematician in me can't let it sit.  The correct formula for the crevice surface area is the difference between the two circle areas defined by the bore diameter and the piston diameter, using PI*r2 where r is half of the respective diameters.  THEN multiply the correct surface area by the crevice depth from the deck to the top piston ring.  I'm sure Baechtel's answer is probably good enough, but this is more correct.

Related Combustion Engine Calculators: 

  • RATIOS AND LENGTHS:
    • Bore (diameter): Compute the Bore Diameter based on the engine displacement, number of cylinders and the stroke length.
    • Bore Stroke Ratio: Compute the Bore Stroke Ratio based on the diameter of the bore and the length of the stroke.
    • Compression Ratio: Compute the Combustion Ratio base on the minimum and maximum displacements of the cylinder at the beginning (1-Induction) and compressed (3-Power) portions of the combustion cycle (see animation)
    • Displacement Ratio: Compute the Displacement Ratio based on the volumes at the beginning and end of the stroke.
    • Rod Length Stroke Ratio: Compute the Rod and Stroke Length Ratio base on the two lengths.
    • Stroke (length): Compute the Stroke Length based on the total engine displacement, number of cylinders and the bore.
  • VOLUMES:
    • Total Engine Displacement: Compute the Total Volume (displacement) of a Combustion Engine based on the bore, stroke and number of cylinders.
    • Engine Cylinder Volume: Compute the Volume (displacement) of a Engine Cylinder based on the bore and stroke.
    • Engine Cylinder Overbore Volume: Compute the Volume (displacement) of an Engine with an Overbore based on the stroke, bore, overbore and number of cylinders.
    • Rotary Engine Equivalent Displacement: Compute the Equivalent Volume of a Rotary Engine based on the swept volume and number of pistons.
    • Compression Volume (V2): Compute the Compressed Volume of a Cylinder when the piston is at the end of the stroke and the chamber is at its smallest (and most compressed) volume, based on the chamber, deck, crevice, chamfer, gasket, valve relief and dome/dish volumes.  This is the second volume (V2) in the Compression Ratio calculation.
    • Gasket Volume: Compute the Volume of a Gasket based on the inner and outer diameters and the gasket's thickness.
    • Deck Volume: Compute the Volume of a Cylinder Deck based on the deck height and the bore.
    • Chamfer Volume: Compute the Volume of a Cylinder Chamfer based on the cylinder diameter and the chamfer height and width.
  • SPEEDS AND RPMS:
    • Piston Speed: Piston Speed (mean) based on stroke length and RPMs.
    • Max Piston Speed: Max Piston Speed based on stroke length and RPMs
    • RPMs: RPMs based on desired piston speed and stroke length.