Here you go, Piston area and force.
Dale
You are 100% wrong in post #125, with 'PSI spread over a larger area creates more force'. Look at post #130. Pressure = force divided by area. The force or pressure [ or whatever you want to call it ] is created by the expanding gas. I used an example of 1000 what-u-ma-call-its. Call it what you like & whatever quantity. The point is that the loading per sq in is less on the bigger piston even though both small & large pistons had the same initial force/pressure applied. That is what the picture in post #130 shows: the flat coin did not sink into the plasticine as it did on it's end because the loading per area was less even though the same initial force was used.
I have already given this example, but maybe you missed it. The piston transmits it's load to the crank via the pin & conrod. If I make the rod eye wider, according to your theory, because I have increased the area, the rod now transmits more force to the crank & the engine makes more hp!!!
Increasing the area of the piston should increase the weight of air drawn into the cyl. If it does that, then the pressure generated from the burn has increased. It is this increase in gas pressure, not the piston area that has created more force.
Pressure - is a value exerted equally in all directions.
Force - is a value exerted in one direction.
In a cylinder;
Force is equal to the pressure exerted on an object × the area the pressure is applied to, in our case -
Pounds per square inch × the area of the piston, or more easily referenced as the area of the bore, in square inches.
OR, pounds/square inches × square inches. NOTE, the square inches cancel eachother out, leaving pounds force.
Obviously the same pressure, in PSI, acting on a smaller piston will exert less force pushing that piston down. Conversely a larger piston with the same pressure acting on it will exert more force.
Given a given cylinder pressure, it acts equally on all surfaces of the cylinder. A larger or smaller piston has no effect on the pressure acting on it, the pressure is the same. Now this is accepting we "freeze frame" the piston motion at say TDC.
Increasing the area of the piston "can" increase the mass or weight of air drawn into the cylinder, if the stroke is the same. This "may" increase HP, but that is dependent on a number of other factors. The main one there is camshaft LCA and duration, which affect where in the RPM range the torque peak will occur.
In post #133, you stated you still do not get it, force and pressure. Obviously you are correct in that when dividing you pressure by the area instead of multiplying. Back to science class you go.