Life Without a Filter

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VStar650CL
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2004 Nissan Altima 2.5 S

Life Without a Filter

Postby VStar650CL » Fri May 07, 2021 2:30 pm

Spring is here and I guess it really is the loony season. I hear people going on again about cold air intakes (which aren't really cold) and K&N's (which are a guaranteed ticket to short engine life and don't work anyway), and if I had any hair left I'd pull it out. For those who care about actual engine science, this is real science, not the marketing crap spewed by K&N and other manufacturers of BS filtering products:

https://www.sciencedirect.com/science/a ... 7316301475

To save you a little browsing, here's a snapshot of the manifold pressure drop for OEM vs K&N, along with the researchers' comments. Surprise surprise, forget better breathing:

Pressure Drop 1.png
Pressure Drop 2.png
That's probably due to the large cross-sections of the K&N "fibers" creating aerodynamic disruption, but of course it's a direct contradiction of all that happy marketing misinformation. Now here's the unsurprising part, no filtration worth a nickel:

Filtration.png
Consider for a moment that your engine digests 9,000 gallons of air for every gallon of gas. That's 45% more utterly unnecessary crud eating up your precious rings and cylinder walls. I won't even go into the fact that with a K&N cone, now you're picking up hot radiator air instead of the nice, cool breeze from your grille delivered by the OE setup. AZ and others here have already made that point better and clearer than I would. The point is, unless you're going to go full-custom hood scoop, don't bother with the induction because the aftermarket solutions will cost you ponies and not add them, and send your engine to the JY early to boot.


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AZhitman
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Re: Life Without a Filter

Postby AZhitman » Fri May 07, 2021 5:30 pm

It's a long and arduous argument.

People will sell their souls for marketing hype, not realizing those marketers are paid HUGE money to convince them that "this intake makes power" or "this cream will burn fat" or "this soap will get you laid."

Here's some more reading, for those who still guzzle from the marketing trough: https://www.nicoclub.com/archives/kn-vs-oem-filter.html

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PapaSmurf2k3
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Re: Life Without a Filter

Postby PapaSmurf2k3 » Mon May 10, 2021 2:20 pm

Yup, what's even worse is when the factory plastic (insulated) intake tube is replaced with a shiny aluminum one that just sucks up heat from the engine bay.
If its bigger, I can understand, but a lot of them aren't.

One thing not mentioned is the ability to change filter geometry though. There are some kits out there that utilize the factory intake plumbing (bringing in air from outside/grill) and replace the factory "box" with one that can hold a cone filter instead of square. The article said they used a cylindrical filter, but doesn't show what kind or if there are any differences.
Its also a little sloppy with its labeling (what particle size were they using for filtration efficacy, graphs, etc) , and their stand-alone tests don't exactly jive with their vehicle performance tests.
acceleration test.JPG
Note they don't mention the parameters for the test (0-100 km/h?) unless I missed it.
fuel economy.JPG
They mentioned the real world filtration of the K&N is likely much better than what they reported, but don't go into too much detail why other than "more of the filter would be used" or something.

For the graphs you posted relating to pressure drop, it would be good if they continued the graph beyond the 3500 RPM to have better separation between the groups. The OE filter shows about 1.55 kPa vs what... 1.85 kPa for the K&N? That's extremely negligible (0.043 psi for the people out there using freedom units), and within the realm of equipment error (which they even mentioned is entirely possible, given that they put the meter in the elbow of the intake and are likely picking up turbulence).

Ultimately I think there's better studies/reports out there.

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VStar650CL
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2004 Nissan Altima 2.5 S

Re: Life Without a Filter

Postby VStar650CL » Mon May 10, 2021 2:37 pm

You still won't bolt on any meaningful horsepower, and you'll still end your engine's life early even assuming the filtration results are off by double. Ugh.

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Jesda
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Re: Life Without a Filter

Postby Jesda » Tue May 11, 2021 3:58 pm

I've seen evidence long ago (LONG ago) of K&Ns working well on older GM FWD stuff, Grand Ams and W-body Regals and such, because the stock airbox designs were not great.

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VStar650CL
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Re: Life Without a Filter

Postby VStar650CL » Tue May 11, 2021 5:18 pm

Jesda wrote:
Tue May 11, 2021 3:58 pm
I've seen evidence long ago (LONG ago) of K&Ns working well on older GM FWD stuff, Grand Ams and W-body Regals and such, because the stock airbox designs were not great.
I'm sure there are induction setups that may benefit a few horses, and whether your engine will die from other causes first is a maybe. It's inarguable that you will accelerate cylinder wall and ring wear, you won't notice it happening, and when a cylinder finally scrubs out, you won't blame your air filter. I'm sure K&N counts heavily on the latter.

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Re: Life Without a Filter

Postby frapjap » Wed May 12, 2021 5:44 am

I remember removing that damned stock air box in the 240s. Anything was an improvement over that constricting and expanding design!


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