# Original H-O'sOtto CyclePower Stroke Calculator

This calculator isolates the "Power Stroke" phase of the Otto Cycle. It computes values from TDC to BDC at 10 crankshaft degree increments. Select an engine and camshaft intake profile or enter your own values. Then click on the Calculate button.

The results table has the following meanings:

• Piston Pressure is the NET pressure on the piston top.
• Rod Angle is the angle in degrees between the bore centerline and the line between the small & big rod end centers.
• Side Thrust is the sidewards force on the piston due to Rod Angle.
• Rod Force is the downwards force on the connecting rod due to NET Piston Pressure over the area of the piston top through the Rod Angle. It is coincident with the connecting rod centerline acting on the crank pin journal centerline.
• Effect Lever is the effective lever arm in inches. Its maxiumum value is half of stroke which occurs at the optimum crank angle.
• Effect Torque is the Rod Force times the Effect Lever.
• Avg TQ is the average Area Under Curve of Effect Torque from TDC to BDC.

NOTE 1: At BDC the Piston Pressure is zero (0 PSI) with respect to atmospheric pressure (14.7psi), i.e., no NET pressure effect on the piston. This is because the intake valve is open greater than 0.050" lobe lift (see IVC ABDC under Valve Events in camshaft specs). Effectively, compression pressure is all leaking out the intake valve.

NOTE 2: To compare engine-to-engine, the C.R. must must be set to the same value not the default from the Engine (parameters) pull down menu. In the real Otto Cycle the starting Piston Pressure will also be dependent on the inlet tract Volumetric Efficiency due to such considerations as carb CFM, intake manifold type, intake port flow and intake valve cam profile. See "Intake Stroke Calculator" for some of that computation.

NOTE 3: Avg TQ is "anti-torque" in the sense that it is subtracted from the Avg TQ calculated in the "Power Stroke" calculator as a component of the net torque in the Otto Cycle. See "Exhaust Stroke Calculator" and "Friction Calculator" for the other "anti-torque" components.

 Avg TQ:
 CrankAngle |Piston|Pressure |Rod|Angle |Side|Thrust |Rod|Force |Effect|Lever |Effect|Torque TDC 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 BDC