Evaluating Water Pressure Sensor for Measuring Pressure in Engine Combustion Chamber

One of the parameters that need to be measured on a fuel motor is compression pressure. Questions to try answered: whether the water pressure sensor can be used to measure compression pressure, considering that the pressure gauge is very useful to use in a motorcycle workshop.

First let’s check what happens to the compression of motor fuels.

In the case of compression, the pressure will increase, and the fuel temperature increases as well. The increase can be calculated with the formula P. V = n.R. T, but the measurement results may not be exactly 100% with the calculation because there is no idea here and there.

The initial pressure of the fuel Chamber is 1 atmosphere, when the pressure compression will rise according to the compression ratio. The Motor is usually a compression ratio between 9.5 to 11.6, so consider that pressure will rise from 1 atmosphere to 11.6 atmospheres. Temperature will also increase, from some reference temperature number around 300 degrees Celsius.

Next let’s check the specifications of the water pressure sensor. The datasheets are more or less like the following link: https://media.digikey.com/pdf/Data%20Sheets/Seeed%20Technology/114991178_Web.pdf

Specifications are important according to the datasheet:

• Wokring Voltage: DC 5 ± 0.5 V
• Working Current: ≤ 10mA (DC 5V)
• Working Voltage: DC 0.5 ~ 4.5 V
• Working Pressure Rate Range: 0 ~ 1.2 Mpa
• Max. Pressure: 2.4 Mpa
• Destructive Pressure: 3.0 Mpa
• Working Temperature:-20 ~ + 105 Ԩ
• Storage Temperature:-20 ~ + 105 Ԩ
• Measurement Accuracy: ± 1.5% FS
• Response Time: ≤ 2.0 ms
• IP65
• Cycle Life: 1 million PCs

The pressure limit is 1.2 Mpa, or 1.2 x 9.86923 = 11.843976 Atmosphere, while compression pressure is 11.6 atmosphere, so the sensor is still qualified from the pressure aspect.

The temperature limit is 105 degrees Celsius, so this sensor cannot be used because the temperature of the fuel can reach 300 degrees Celsius.

Conclusion

Water pressure sensor is not suitable to measure pressure on a combustion engine chamber.