Can I increase power by increasing surface area to a piston of a fixed size?
Would there be any power benefit to adding half round grooves to a piston as shown in the pdf? Power being an increase in pounds of clamping pressure exerted.
Well i guess the pdf did not post with the question, but imagine a round piston with a typical flat face. Now take a cross section and draw a circle with the center of the circle coincident with the face of the piston and revolve cut that from your piston. If you had several of these rings on that piston would it improve the clamping pressure of that piston?
Not an automotive engineer, so I’m not familiar with the term ‘clamping pressure’, but I do not see that you will increase the power. Assuming the face of the piston is perpendicular to the walls of the cylinder, the downward force is the pressure times the area of the piston. This force is then transferred to the crankshaft where it is converted to a torque thru the moment arm of the crankshaft.
Adding the grooves (or dimples) still exert the same downward force on the piston. However they also have a non-perpendicular component which exerts a sideways force on the piston. This force should be cancelled due to equal and opposite forces on opposing walls of the grooves.
Engines are very complex machines and saying that just changing the geometry (ie. the grooves you want to cut out) of a design of one of the components is actually just the tip of the ice-berg.
Not only do u change the surface area (total area, not just perpendicular to the connecting rod) your also changing the volume of the combustion chamber which is calculated based off of other variables (air flow, compression ratio, ect.).
Will you create more power due to JUST the increase in surface area?
THEORETICALLY no… The power created by the combustion is due to the normal distribution of pressure from the “blast” that acts on the piston’s face. Now if all of that normal distribution is acting parallel with the connecting rod all of that force (technically not all but the maximum amount) will be translated to the crankshaft. Adding surface area to a fixed diameter does not change the NORMAL contribution.
However, this will change things like “surface area/volume” ratio’s that are dealt with heavily on the thermo-dynamics of the engine and how well heat is transfered. A car suffering from atomization issues (not getting the gas to break down to smaller particles to be burned) may actually BENEFIT from an increased volume or surface area. That is why it is only THEORETICALLY assumed that the grooves you wish to make will not add power.
Also a nasty lil problem that comes with small grooves in the top of the piston is that unburned gases (yes not all the gas in a cylinder is burned up) tend to stick and build up around corners or scrapes. Just look at a well used valve or spark plug and you’ll find there’s usually a build up of black soot or “tar” … thats carbon deposits and any time they start to accumulate power is robbed. So if you do find an increase in power due to any effect of the grooves, it will probably be extinguished in the long run and maybe shorten the life of the engine.
