Air filters, the same old arguements go on

booster

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I was at the auto parts store the other day and they also sell some speed stuff. There was a "discussion" going on as to what air filters are best and if cold air packages actually do anything.

I have been into cars, engines, horsepower, etc for about 60 years and over that time one of the perpetual discussions is around air filters and what is best for horsepower, filtration, lifespan, plus whatever else folks came up with at the time.

I have basically run the perceived higher end paper element filters in all the stock cars as they are never going to be "fast" or see the high rpms that need massive airflows. Of course, they would benefit a bit from low pressure drop over all airflows, but not as much because that drop is low at low flows, and now that carbs are long gone it does not make any difference in mixtures at all, and not much in response and things.

On the engines that I wanted to make maximum power I used K&N for the most part. Mostly because of the low pressure drop because I was building turbocharged engines and turbos hate inlet pressure drops. The most powerfull was a twin turbo Dodge 340cid engine that made 600hp back in the 90's and was very fast for those days.
On the stockers, I have never seen much of any dirt on the clean side of the intake ducting as long as there were no leaks in the system. On the K&N ones there would be some light dusting in the areas where the airflow slowed down due to shape of the ducting. The turbo engine had a long inlet tract as it went through an intercooler also.

We have never had any oil burning in the stockers with highest mileage of 212K miles. No oil burning in the turbo engines either as long as they had the right pistons and rings in them, fitted correctly. The highest mileage on the turbo engines was 50K when I tore one down and it did not show any excessive wear, though, with the K&N.

My opinion, and it is just that only is that the K&N filters do pass more dirt, but it is unknown how many miles it would take until it made a difference, if any. We are using Wix filters for oil and air currently, and never use Fram anything anymore after a huge oil filter failure.

The auto parts store overhear made me decide to take another look for good information on the subject as in the past there was only manufacturer claims and backyard testing available and I consider both to be borderline useless if you want unbiased accuracy.

I ran across this article that actually sent filters to a commercial testing company for testing. The article's writing might indicate a bias toward factory products, so keep that in mind when you read it, if you are interested. The article is from 2009.

The results make some sense to me. The best rated filter had the highest pressure drop and lowest dirt allowed past them which is how filters almost always test. It was interesting how some of the middle ones had better combinations of pressure drop vs filtering than others in various ways.

https://www.nicoclub.com/archives/kn-vs-oem-filter.html
 
Hey booster!

Thanks for another Rabbit Hole!;)

Interesting to note they test ran at 350CFM.
The LS (NA) typically would look for 650-880 CFM ~ no?

The filtration they evaluated was just the filter, assuming it would be in some sort of Cold Air Intake (CAI) setup. Clearly, they were limiting the variables to focus on filter comparison.
From the test write-up:
"...The stock filter will flow MORE THAN ENOUGH AIR to give you ALL THE HORSEPOWER the engine has to give. "
Except when comparing a Chevy stock LS filter canister arrangement to even a short Cold Air setup. The focus of the testing was filtration - the job of a fliter. But, these filters are intended for a CAI - and some attendent HP gains. It becomes a balancing act of a CAI + Filter.

These "notes " from JEGS: (obviously selling to performance-minded clients)
attachment.php


The downsides note exactly what the 2009 test pointed out:
attachment.php


And this one from Banks - with a purpose built system (not RT):
attachment.php


It would be interesting to run a CFD analysis on a simple CAI vs RT "Stock", but am deeply involved now on a major effort with other "C-3DarkWerx" projects.

Cheers - Jim
(actually iw was a welcome break from crunching numbers...)
 

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There is not question if you can reduce air temp, you can make more hp and max rpm and/or hp point with a low restriction filter. The fact that the stock ones can flow enough doesn't take into account the pressure drop needed to do that so that can affect the actual flow. The devil is in the pressure drop the filters are rated at. Flow is also affected by the entire intake track so a single tube with an air filter on the end will always do better but not better than no air filter.


You can tell from the article that actual hp was not the focus or the OEM filter wouldn't have been first as it has the highest pressure drop.


You are way, way more focused on hp that we are. I would say our van has hit max hp point probably zero times and for sure never redline, so getting max airflow is not an issue that even makes the radar for us. I am much more concerned about healthy engine lifespan with minimum amount of degradation. Inlet air cleanliness is an issue, but as I mentioned based on our past engines, how good is good enough?


My main beef is with the aftermarket products that are severely, it appears, overstating the quality of their filtering and perhaps giving people bad expectations. For most it probably won't matter much, we are still on our OEM air filter at 70K+l miles so we don't see a lot of dirt where we go. Somebody who is offroading all the time at high rpm might or might not.


I think, based on the test, if it is accurate, any of the top three or four would probably never be an issue unless the seal was broken and you got a bypass leak. The lower ones, who knows for sure. OEM, Baldwin, Wix, etc are all very good companies when compared to Fram and such, IMO.


I think that the article is very good for those concerned with air filtering quality. There are lots of articles and testing out there for which make the best hp for those are more focused on that.
 

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