I recently did the LHT airbox gutting mod and barely noticed a difference, until I swapped in a K&N and now it sounds pretty good - I quite like it.

But I’m concerned because there’s a lot of mixed sentiment about drop in K&N filters, due to the reduced filtering capability. I like the sound, but not the stress.

Has anyone run this filter for many miles and proven that the engine runs fine with it? If so, how many? Any 200k+ engines with a K&N here?

Or has anyone proven the opposite: the filter actually did more damage over time?

 

Its not about miles. Its about silicates in oil. What you really wanna ask, who did a before and after oio analysis w k&n filter vs stock, what were results?

I bet there is a thread on this you could find. A much better answer than miles

 

I seen a bad oil analysis on a BRZ recently that was loaded up with a large amount of dirt as it went off-course at a track. K&N type filters are terrible if loaded up in a dusty and dirty environment over a short period of time. They filter better over time as they get more dirty. Keep the filter area clean and free of dust and big amounts of dirt and you might be okay. The filters let in more dirt and larger particles of dirt, no question about it, whether it is enough to affect wear is hard to answer. Check a used oil analysis for silicon content and then see if it corresponds with extra wear, you will need historical data to compare with. I've seen a number of reports where the increased air flow from K&N style filters do nothing for power , they may sound different or better, but not necessarily make more power. The S2000 OEM filter has enough surface area to feed a V10 motor in terms of airflow , so it doesn't need more flow. A BRZ oem air filter makes the same or more power than an equivalently sized K&N filter. Cotton gauze filters do flow more air - as you can see in the little advertising promotional displays at auto parts stores, but it doesn't always translate to more power, if there is no more power to be found why bother ? Maybe lower cost over a number of years - cleaning vs. replacing with new filters ? I don't think it is worth the risk.

 

I have a few friends who've ran the K&N filter for over a decade and have at least 180k on their engines. The concern is warranted but their engines haven't grenaded yet. I agree that the filter is less effective at actually filtering, however.

As far as the airbox mod, it is actually detrimental to airflow with respect to fluid dynamics. In the original design, the air is rammed directly into the filter with a series of ducts that connect to the intake opening and dumps the air directly into the filter. The filter is constantly being rammed with fresh cold air as the car moves forward as is typical for scavenger ram-air cold air intake. Excess cold air that doesn't go through the radiator is pushed up through the radiator cooling plate. The plate has a series of bends in it to create high pressure streams of air and guide them towards the intake cleaner box. The hood is the second piece of the puzzle which blocks off the air and guides it towards the intake. So, to me, the idea of heat soak in the air cleaner box doesn't make much sense. If it's the ambient temperatures in the engine bay causing issues, it's unavoidable as the filter is constantly being replenished with more air. Increasing the volume in the box merely reduces the efficacy of the intake as it has to vacuum a larger volume. By removing the ducting, you're forcing air to change direction in an unnatural way which creates drag at the intake and reduces its efficacy. Rather than the ducts guiding the air and helping it change directions, the air falls into the box, hits the back wall, tumbles, and then begins to get sucked into the filter which reduces velocity. There is still drag involved with the 90 degree bend in the ducting attached to the lid. However, the air is being aided by the vacuum of the filter sucking it through the ducts. The airbox mod creates turbulence inside the box which isn't great for performance. Someone on here did make a modification which I think is beneficial in conjunction with the air box mod where they routed a duct from near the wheels up into the airbox and I think that is beneficial as it allows the entire filter's surface area to draw in air.

The intake is a very efficient design which has guided intake designs for Honda since it debuted. The FE1 Civic Si, FL5 CTR, DE4 Integra and DE5 Integra Type-S use the most modern version of this intake design, though the screen filter is less efficient than a cone filter as it has less surface area. I think the PRL design for the FL5 is a really nice change. The air doesn't have to change direction as much and just dumps into the filter box. But you can see this design in everything from the MDX, RDX, Pilot, ILX, TLX, CRV, and literally everything else. You'll also see that other manufacturers use some version of this intake as well.

 

I agree that many people have ran those kinds of filters for many miles and never reported issues. It isn't something that is going to destroy your engine, I don't know how you could ever determine how much extra wear could be caused by higher levels of dirt and dust flowing through the engine.

 

Totally, that’s sort of why I was hoping to use miles as a proxy. Silicate content is a data point
, but… not sure what to do with it.

 

Extra dirt is acting as abrasive on your piston rings and cylinder walls. While the engine will not grenade, maybe the Oil consumption rises.
The Honda Air filter is remarkable, while made from Paper, it is fuzzy and oily. It is made different. Maybe for a reason?

 

This. And its impossible to know the effect. Your engine will consume more oil bc of using a k&n filter. The question is, is it something trivial, like 1% more, or something not trivial like 25% more?

Risk vs reward.

Risk = some level of engine damage. Unknown how much.

Reward = it sounds kinda cool. Thats it. No performance gain. Just sound.