Engine Air Filter Pressure Drop

Automotive engines require a lot of air as part of the internal combustion process.  Anyone who has lifted the hood on their automobile knows that the air coming into a vehicle engine is filtered to keep out road dust and grit from entering the engine cylinders.  All vehicles have an air filter for this purpose and these are commonly made of a paper filtration material, are housed in a plastic or metal can, and can be opened easily for filter replacement.

One way to verify filtration efficiency is to measure the pressure drop across the air filter at all times during test track engine operation. The diagram shows how this can be done using a Validyne model P55 pressure transducer. The best design of an air filter is one that allows a lot of air to pass with a minimum loss of pressure, and a lot of effort goes into filter design that can provide a large surface area in a small space – even an ordinary air filter contains dozens of folds to achieve this.  A clogged filter will lower engine performance and the best method of determining how well a filter is operating is to directly measure the pressure drop across it. External Link on influence of air filter on car fuel consumption.

The pressure drop across a working engine air filter is often very small – on the order of a few hundred Pascals, especially at low engine RPM – so a pressure sensor for this purpose must be sensitive to very low pressures.  In addition, the pressure transducer must be rugged enough to function well under the hood of a vehicle where shock, vibration and high ambient temperatures are common.

The Validyne P55 pressure transducer meets these requirements.  The P55 pressure transducer is rugged and compact and can be mounted inside the engine compartment.  This pressure transducer is available in very low full scale pressures so that small pressure drops across the filter can be measured under test track conditions.  The P55 signal can be connected to any data acquisition system that accepts the ±5 Vdc signal.

Validyne has also supplied a variant of the P55 pressure transmitter that has been designed for use in military vehicles to measure air filter pressure drop. This is important in desert environments where dust and grit are often present. The P55 electronics in this version has been secured with epoxy inside a special housing.  The electrical connector and custom mounting plate provide a sturdy attachment to the air filter enclosure.  A 4-20 mA signal is used by the engine control system to alert the driver when the air filter starts to clog.  This allows for preventative maintenance and a way to avoid stalling the engine in challenging conditions.

If you would like to replicate this application or want more information on how a pressure transducer can be used to measure pressure drop across an air filter, please do not hesitate to contact us at sales@validyne.com.