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How to Measure Engine Air pressure Drop Using a Pressure Transducer


The internal combustion process in automotive engines requires a mixture of fuel and air to operate properly. If there is a lack of air, the gasoline doesn’t burn sufficiently to produce the energy required to power the engine. However, it is very important to ensure that only clean air reaches the engine. This is due to the fact that dust and dirt leave the engine susceptible to debris rubbing the metal parts of the engine, which causes damage. Especially in military applications, where vehicles are often subject to dust and grit due to operations in harsh environments such as desert. For this purpose, air filters are installed in automotive engines to increase the fuel efficiency of vehicles and deliver clean air to the engine. These filters are made of a paper filtration material and are housed in a plastic or metal can. However, continuous exposure to dirt results in the clogging of filter, which affects the fuel consumption and performance of the vehicle.  To prevent this from happening and gaining the maximum out of these air filters, they need to be replaced every once in a while.

With this arises the question of when it’s time to replace the air filter of the engine. To determine this, the efficiency of the filtration process is timely monitored so that any discrepancy is spotted beforehand. Air filter pressure sensors are deployed in this case to measure the pressure drop across the air filter at times during test track engine operation. Ideally, an air filter should allow a lot of air to pass with a minimum loss of pressure and provide a large surface area in a small space. This implies that the pressure drop across an air filter in a perfectly fine working condition is very small on the order of a few hundred Pascals, especially at low engine RPM. Therefore, the best way to monitor the performance of an air filter is to directly measure the pressure drop across it. Additionally, due to very small pressure drops across an air filter, a pressure transducer sensitive to very low pressures, vibrations and high ambient temperatures should be used in this case.

A rugged and compact sensor such as the P55 differential pressure transmitter from Validyne Engineering is ideal for this kind of application where small pressure drops need to be measured. The transducer is available in very low full scale pressures so that small pressure drops across the filter can be measured under test track conditions. For use in military vehicles, a special variant of P55 pressure transmitter has been designed to operate in environments where dust and grit are often present. The pressure transducer can be mounted inside the engine compartment. It also has the security of epoxy inside a special housing. It is attached to the air filter enclosure with the help of an electrical connector and a custom mounting plate to ensure a sturdy attachment. The engine control system uses a 4-20 mA to alert the driver when the air filter starts to clog.

Hence, knowing when to replace the air filter of a vehicle benefits the owner or industry in many ways. It’s a convenient way to prevent costly repairs in the future and ensuring that the vehicle stays intact for a longer period of time.

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