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FORMULAS & TABLES

DISPLACEMENT OF EVOLUTION ENGINES: 

    STROKE
BORE

3.498

3.625

3.780

Stock 80”

S & S

Sputhe

3.812

Sportster

73.268

78.685

85.557

4.250

Stock 80”

81.686

87.725

95.388

4.625

 

88.894

95.466

103.805

CALCULATING THE DISPLACEMENT OF A TWO CYLINDER ENGINE:

       Displacement can be determined by the formula: D = B X B X S X 1.5708

Where: D = Displacement
  B = Bore
 

S = Stroke

CALCULATING COMPRESSION RATIO:

Compression ratio can be determined by the formula:

C = D + Vd + Vs + Vc
      Vd + Vs + Vc

 

Where: C = Compression ratio
 

D = Displacement of one cylinder

  Vd = Volume of dish (+) or dome (-) on piston
  Vs = Volume of squish clearance
  Vc = Volume of combustion chamber

To calculate the compression ratio of an engine using Sputhe cylinders the following values may be used.

D = 782cc for the 95.4” kit D = 850cc for the 103.8” kit
Vd = 16cc for dish top pistons

Vd = 0cc for the flat top pistons

Vs = 11cc @ .060” clearance  
Vc = 78cc for pre 1990 heads Vc = 87cc for 1990 & up heads

Example: 1989 engine using a 95.4 ci kit with dish top pistons:

C = D+Vd+Vs+Vc= 782cc+16cc+11cc+80cc= 897cc = 8.54
   Vd+Vs+Vc     166cc+11cc+80cc 105cc   1

 

FORMULAS FOR CALCULATING TORQUE & HORSEPOWER:

T = Hp X 5252

Hp =

T X rpm
             Rpm              5252

TABLE OF EQUIVALENTS:

1 inch = 25.4 mm  1 cubic inch = 16.387cc
1 mm = 0.039371 inch  1 liter (1000cc) = 61.024 cubic inch

 

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Grass Valley, CA 95949-9715

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