Engine Air filter.. Does pre filter reduce mileage efficiency?

I agree that there was some question about sealing of the air box. Frankly, I can't say I read the entire thread (sometimes boring). I don't remember if Dragos actually posted a comparison of the air filter seals to determine if the dimensions were identical.

For me, the result of higher airflow with less pressure drop is contrary to engineering intuition: It's well known that the lower a filter's micron rating, the higher the pressure drop, and the higher the percentage of particles removed. The percentage of particles removed varies according to the micron diameter of the particles. The finer the particles, the more difficult it is to filter out a high percentage of those particles. The more effective a filter is for any size particle, the greater the pressure drop and flow reduction. Manufacturer tests of filtration efficiency will have a table of particle micron diameter range and the percent of the total percentage of particles removed in that range.

Review the manufacturer test data for pleated paper vs. oiled. If this is K&N marketing, then they won't provide the test data if it compares unfavorably. It is your decision regardless.

 

https://www.knfilters.com/efficiency_testing_procedure.htm


"In most aftermarket intake kits, companies supply their product with an oiled filter. Oiled filters flow more air through their media because they are constructed from a more open cotton material that is coated with a thin layer of oil.
Generally, high-performance dry filters can catch up to 99% of the incoming contaminants due to the smaller micron size of the filter media, while oiled filters catch about 98% of what passes through – a minute difference, but a difference none-the-less.

The oiled filter material relies on the tackiness of the oil to catch contaminants while the more open media allows a higher flow rate. The oil acts as a sticky trap for incoming air contaminants, providing an important layer of protection to keep the air free of debris. These filters typically come pre-oiled with a specific amount so they can drop right in without the user having to do anything. Oiled filters are what you see in most race applications (excluding off-road). Many companies offer a direct drop in replacement for the stock air filter, and often, there is a slight bump in performance.

Another benefit is that these filters can last a lot longer than their dry counterparts. Oiled filters have the advantage of being completely washable and reusable, so you don’t have to keep buying filters once they become too dirty. All you must do is follow the instructions to clean the filter and you’re all set! However, with greater airflow from these filters comes great responsibility. Oiled filters must be regularly cleaned, maintained and properly oiled, or else they can become detrimental to performance. You may have also heard that oiled filters can damage your mass airflow sensor (MAF). Let’s nip this right in the bud. Usually the only way for something like this to happen is if you over-oil your filter when re-applying the oil. If there is too much oil on the filter, some of it can get sucked in through the cotton gauze and damage the MAF sensor. This is where you must be careful and follow the instructions on how to clean your oiled filter."






In my experience I prefer using oiled filters. Not a lot of difference in filtration efficiency compared to dry. Both types have their advantages. Many filter manufacturers are providing an oiled cotton media filter option such as aFe, S&B for instance. The TRD filter is oiled. Comes down to a matter of preference. Maintenance free dry filter or a reusable oiled filter that does require some minimal attention from time to time? Comes down to personal preference.
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So which is better, the K&N or the TRD? I would think the TRD because it's performance has been tested by Toyota.

 

Not hating on anyone who uses an aftermarket filter and/or CAI. I’m a believer in the principle that if you own it, do as you please. I’ll just stick with the OEM filter myself. I figure if there were a filter that provided a significant gain in power and/or efficiency, it would come standard on the truck. JMO.

 

It's offered by Toyota as an accessory.

 

I agree with your statement, but added some caveats in brackets to reflect other considerations by manufacturers.

 

Only thing certain when it comes to filters is that FRAM is garbage.

 

Because they know some people will buy it.

 

I agree 100% with your caveats.

 

K&N used to make the oiled TRD drop in filters and may still. The current TRD filter for 2nd & 3rd gen Tundras is virtually identical to the K&N except a different color and uses gold oil instead of K&N red. Same polyurethane body and the same exact 4 progressive layers of cotton gauze media. Set them side by side. Identical. Both are very flexible. TRD is not aFe. aFe uses 5 progressive layers of cotton gauze media with their 5R series and not quite as flexible as the TRD/K&N. The aFe costs more than the TRD/K&N and filters a bit better for around $85. The TRD is marked up more than the K&N because it's "TRD". FYI. The TRD oil filter and K&N are the same and both made by Frampion. Some aFe dry filters only use 3 layers. aFe offers more choices oiled and dry depending on budget and use. I have to give the nod to aFe on that.

 

But Toyota has approved its use and meets all their requirement.

 

I’m not saying there’s anything wrong with it. I’m saying you don’t get any significant gains from it.

 

The main gain is you buy it once and never have to buy another air filter again.

 

The prefilter materials is just like the furnace filter material, ie like fibreglass NOT foam.

 

I have used KN drop in, Kn CAI or AFE CAI in the past, on 08Tacoma, 06 Tundra, F150 they definitely change the way the engine breathes for better. I have felt some performance gains in HP, not in terms of mileage.

 

K&N works because the marketing says so. See, even you're a believer.

 

You get it

 

Worked for 48 years so far. Why pick on only K&N? LOL...
Why not aFe, S&B, and many other makers of...emphasis on..."reusable" oiled filters? They all make the same claims of increased air flow and some hp gains which is somewhat true at higher rpms. I clearly stated that I use K&N because I prefer reusable oiled filters. That's my preference. Why does it bother you so much that I use K&N's over the years along with millions of other satisfied users that apparently know how to properly oil them???? I sense an "insane" case of K&N Derangement Syndrome.....LOL

By the way what air filters were you buying for your MX and 4X4 back in 1972? Oh wait......

 

When I replaced my crappy Fram last week, I removed that prefilter. My grandson got a hold of it and ripped it up. The pieces had the consistency of firm foam but didn't didn't appear be made from fiberglass particles.