Q&A With Stuart Miyagishima

Published in the May 2019 Issue May 2019 Ask The Expert, Feature Steve Janes

Recently we were able to catch up to Stuart Miyagishima, part owner and vice president of engineering at aFe Power, and ask him some questions about air flow requirements in diesel trucks.

Since all trucks require air filters, we thought it would be a good time to find out a little more information about the function of these filters and how they can affect the performance of our diesel engines. Here is what we learned.

 Q—What are the difference in airflow requirements between a diesel engine and a gas engine?

A—Requirements for both are based on engine size and redline rpm; the difference is the volumetric efficiency of a diesel vs gas engine.

 Q—Do all diesel truck engines (Duramax, Cummins and PowerStroke) have similar airflow requirements?

A—As above, requirements are based on engine size and redline rpm.

 Q—How does the flow rate of an air filter affect the performance of a diesel engine?

A—Additional air flow will increase the performance, up to a certain point. Beyond that, you add more fuel to take advantage of the extra air available.

 Q—Are all air filters created equal? (Briefly explain the differences with the pros/cons of each.)

A—No. OE filters are one-time use, typically lasting 15k-30k miles.  The media can be paper or synthetic, seals can be foam or a rubber gasket type seal. The washable/replaceable (performance) filters are designed to last longer, often times the life of the vehicle. Again, materials of construction, media and seal design will vary from manufacturer to manufacturer. You have choices now, from oiled cotton gauze, dry synthetic, oiled foam, just to name a few.  The purpose of these is to provide more air to the engine.

 Q—Are OEM filters always the best choice? What are the advantages of aftermarket filters?

A—Not necessarily. As mentioned above, aftermarket filters come in a variety of media, each with a specific purpose.  At aFe, we offer 4 different media: high flow oiled cotton gauze (performance), dry synthetic (convenience), high efficiency (protection), and long service life (high dust-holding capacity).

 Q—Which technology has gone into the construction and material used in an air filter?

A—With reference to the aFe filters, we started with the oiled cotton gauze filters and looked at what we could do to be different and maximize the performance (air flow). For the media, the number of layers, thread count and oil were all zero based. The pleat shape and number of pleats were analyzed to optimize flow. Our oil is a special formulation that addressed a lot of the concerns people had with an oiled filter. Likewise, the seal material, seal design and filter frame were all scrutinized. We completely box the frame on all sides for our flat panel filters, which gives it great rigidity and won’t allow the seal to slip off the sealing surface. All our filters use polyurethane for the seals/ends, a very durable material that withstands the harsh under-hood conditions. After that, we looked at making a high efficiency filter, and there we combined the oiled cotton gauze with synthetic media to create a hybrid media that we call Pro GUARD7, which worked so well and was so unique that we have a patent on it. Subsequently we have introduced a dry synthetic media and long service life media, but all our filters feature the same attention to detail.

 Q—What is the life span of an air filter under normal driving conditions? 

A—As mentioned above, life span of an OE filter is typically 15,000-30.000 miles, while many aftermarket filters will last the life of the vehicle.

 Q—Which type of driving conditions have the most negative impact on air filters? 

A—Moisture and very dusty environments. Moisture on a paper filter can ruin it. That is why you see them with a fine layer of oil. Very dusty environments will clog up your filter faster, the smaller dust particles can get past the filter and get to the engine. The advantage of the oiled filters is that the oil helps repel the water, but that will not work if you submerge it (no filter will work well when submerged).

 Q—When is it time to replace your air filters? How do you know?

A—Typically the OE filters are replaced at certain mileage intervals, unless you happen to drive in a real severe environment and you see that the pleats are clogged.  For an aFe filter, we recommend that you clean it once for every 2-3 times you would have changed your OE filter. Again, driving conditions will have an effect, so we also say that if you cannot see the wire mesh on the filter, it is time to clean it.

 Q—What can you do to extend the effective life span of an air filter? 

A—On an OE filter, there is not much you can do to extend the life other than avoiding exposing the filter to moisture and a lot of dust. For the washable/reuseable filters, it affects the service interval. For the filter on an intake kit (typically conical shaped), you can add a pre-filter that will help extend the service interval. To extend the life of any washable/reusable filter, make sure you follow the manufacturer’s cleaning instructions, and do not use compressed air or excessive heat to expedite the drying process. For oiled filters, put the recommended amount of oil on them. Do not run them without the oil. Due to variations in oils, aFe recommends only aFe oil on its filters.

 Q—How can you determine which air filter is the best for your diesel truck? 

A—We always answer that question with a question: What type of driving conditions are you typically experiencing?  If you are in the city and rarely see dusty conditions, we recommend our Pro 5R for highest flow or Pro Dry S for the convenience of using no oil.  If you are in very severe, dusty environments, we recommend our Pro GUARD7 media for its high efficiency. An option to this on selected intakes is our Pro 10R media, which is our long service life filter. It holds the most dust before clogging but still has excellent filtration efficiency.

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