how much pressure is required to push up and down the piston of a 4cyl internal combustion engine?

Answer 1

b) Dynamic Measurements
For measuring the dynamic cylinder pressure in the combustion chamber of a gasoline engine (Ford 1.4 liter) the SiCOI sensor was placed into the cylinder head with a M10 thread. The engine was operated at 1500 rpm under different loads. For calibration a quartz pressure transducer from Kistler AG was used as a reference. Fig. 6 shows the output signal (pressure) measured with the SiCOI sensor in dependence of the crank angle and time, respectively.

The chart shows about 55 bar, or 798 psi, see website at:

http://www-mat.ee.tu-berlin.de/research/sic_sens/sic_sen3.htm

Answer 2

The previous two "answerers" have some good points. However, an internal combustion (IC) engine only pushes down on the piston. Typically, an IC engine is 4 stroke. The "working" stroke is when the piston has compressed the fuel air mixture and it is ignited by the spark plug. This causes a mini explosion that forces the piston down because the resulting rapid expansion of the gas has no where to exit. Many times you'll hear a statistic about IC engines called "compression ratio." Generally, the greater the compression ratio, the greater the pressure on the piston when the ignition occurs. The compression ratio is the ratio of volume of fuel and air when the piston is in its fully extended (or down) position to the volume when fully compressed. You'll typically see ratios of 8:1 or 10:1. In higher performance cars, that ration might be higher. That means the fuel has more "push" per stroke. The force per unit area (or pressure) is the result of the force of the explosion on the (usually) circular piston head. The pressure would be calculated as the force divided by the area of the piston head.

Answer 3

It depends on so many variables. What is the resistance? Is the crank shaft free to turn, not coupled to a transmission? Are you using a forced gas pressure through the sparkplug hole? How big is the piston, how long is the throw on the crank journal?

Answer 4

Depends on the engine displacement.

Bigger cylinders=bigger pistons=more pressure required.

Typically, the amount of pressure you get from burning the amount of gasoline in the cylinder.