DIY: Secondary Air Filter Removal

K&N drop in is crappy filtration.

 

So I haven't done this to my 4.0 and likely won't. However let's think about this logically, and I bring this up only because in my first 20 pages of skimming I didn't see this get brought up. To those saying the screen presents absolutely no restriction, I say you're incorrect. Imagine a completely open pipe with a single strand of thread stretched inside it at 2 sides. Albeit extremely minimal as in .000001 minimal there is still an impedance. Multiply that by however many strands make up this screen and that creates more impedance. Sure it's still minimal enough that that it produces any real significance but it is still restrictive. If tiny fibers don't make a difference then why do Olympic swimmers shave their arms and legs and wear caps. To shave .001 off their time is why.
As far as dyno results are concerned, sure I have no doubt that a 10 second pass at WOT didn't yield a difference. Has anyone ran it in a dyno for a solid 3.5 hours or however long it takes to burn a whole tank? I doubt it because that would be ridiculous. To truly find the answer for this would take a weeks and weeks of extremely well documented drives in ideal driving conditions to prove or disprove.
Could this mod be snake oil for the 4.0? In a nutshell is so that's mostly true because the real world gain may only be measure able over multiple tanks and pretty much is perceived as "no gain". Just my 2 cents.

 

Except there are industry standard tests that are actually designed to compare more accurately than multiple tanks and the wmany uncontrollable variables. These test prove without a doubt that a restricted intake doesn't reduce mpg, if indeed you are talking mpg, you're not specific about what is a gain, other than multiple tanks implies you are talking mpg. 3.5 hour dyno test?

If the filter can flow more than the engine can it doesn't matter if there is restriction.

The logical assumption that a restriction means a reduction in mpg has been proven wrong.

http://www.fueleconomy.gov/feg/pdfs/Air_Filter_Effects_02_26_2009.pdf

 

Just a shot in the dark but as opposed to tearing out filters that seemingly net 0 results has anyone tried some type of thermal insulator on the OEM intake tube similar to what's used on intercooler pipes to try and lower the intake air temperature by reducing the affect of the ambient heat coming from the engine on the plastic piping and assumingly keeping the intake air as dense as possible? Honestly it'll probably look like crap but if it reduces intake temp then maybe it'll make a very small difference.

 

California's smog check on new cars is now pretty simple, they only connect it to a computer to make sure the computer is functioning and doing what it is supposed to do for emissions, the inspection they use to do wasn't done on my 04 BMW, when I asked, they told me the above. At least this was my recent experience, but who really knows, after all like it was said, it is California...

 

So 8 months later I'm looking at this and decided to check it out. This secondary filter looked pretty dirty. I've only put 5k miles on it and it had a new filter. I had taken it out and put a drop in K&N filter in. I went off road a couple times and it was turning black, so I put the paper filter back in. Wondering if the dirty secondary filter is from the K&N filter or the stock paper filter.

 

K&N filter is to blame.

 

That seems to be the call me an answer. common answer. I've heard that so much that when it's time to put a snorkel in a new cold air intake I'll be looking at other manufactures.

 

Common answer

 

Yep. I took that thing off today from my FJ’s TRD CAI. Just needed a flat head screwdriver. Useless to drill anything, it will pop out just pulling.

I can’t say any difference after 250 mile driving.

 

So how would I do this for my 2018 3rd Gen? I have an L4 and want to increase the power and fuel efficiency.

 

Read the thread, it doesn't do anything for power or fuel efficiency.

 

I'm so confused though. I read the first 2 pages and skipped back here. It took me 1/2 of the OP to realize that the secondary air filter blah blah (usually a separate charcoal cylindrical canister in the engine bay) was in the actual air filter housing. Like...wut...??
Does it filter the air twice, or does it filter different air going to a separate place...?

I'm also really confused how this would affect emissions at all.
It's just so weird to have a permanent air filter that can never be changed.
Did I mention I'm confused?


EDIT: Likely why I'm so confused is my truck came with a goofy "HPS 'high performance' intake on it. I bought a used OEM air housing assembly, waiting for that in the mail. I haven't looked too closely at the intake currently on the truck, but I didn't see many secondary hoses running anywhere - something that alarmed me a little bit as I've noticed all/most modern vehicles have at least a couple vacuum lines on the intake.

 

took mine out a few days ago,,,I think it's better indeed. The AFE PRO DRY S is on the way. Now to monitor the mpg & see.

 

This matter is all about "Restriction VS. Filtration"... You cannot relatively argue with physics...but you can take standard measures. For example, I made a diy-CFM tester with a knife, cardboard box, hairdryer, paper, duct tape, a few zip ties, and etc! I was not aiming for an accurate peer reviewed published scientific study/measurement for you guys... "but"... I can assuredly say this; Given a few relative contstants (temp, humidity, steady airflow, etc) AKA in my living room with this redneck engineered rig), I observed a very noticeable difference. I cannot argue there is a definite measureable amount of restriciton present with the secondary filter in place. . Anything in the way of free airflow will cause restriction to some degree.

I figure thatsince most of the arguments boil down to Restriction/Filtration/Flow/Safety issues! The engine intake components and related sensors can be affected over time if certain conditions manifest themselves given a few variables. All that means is choosing between filtration and safety or flow and risk possible outcomes!....

In my case I can say that I have a pair of KN filters i have been maintaining for approx 68k miles now. I rotate them out semi frequently, clean them, "PROPERLY OIL" them, and most importantly...keep an eye on the MAF sensor and inner intake tube housing! I have only had one instance where i put a fresh from the box KN filter in the airbox and had some oil buildup in the intake tube with the secondary filter removed. No permanent damage was done! I simply disassembled the intake tube, cleaned it out thoroughly with lint free wipes and use some CRC sensor/electronic cleaner on the MAF. Just a quick spray....nothing more than enough to clean it! I currently have 118k miles on my TRD Taco and have had no other issues.

I have never had my vehicle dyno'd. I have also not noticed any statistically significant changes in performance either. What I do notice is a free sounding intake that seems pretty free of restriction and a nice free revving throttle response. I do notice my idle settling lower and my vehicle shifting at lower rpms relative to throttle position and speed. I also have the TRD exhaust and enjoy the sound very much.

I can say this with a relative amount of certainty. Im not sure there are any quantifiable gains in hp/torque/0-60 times/etc... but i will say my taco feels and drives like it breathes alot better and drives like it has more power. My Taco revs smoother and tickles my ears when it does! I like it an I have seen no instance of damage or negative affect on fuel mileage. If anything I can say i believe I fill up less often due to the lower rpm ranges my truck seems to operate in. If I notice anything queatifiable with fuel mileage I will report back. I have to say honestly I dont care....because my truck sounds and seems to breathe better to me...thats all I care about is my experience when I drive it....period!

I hope this helps quell the debate a bit. Enjoy and thanks for reading!

 

If you are driving for improved MPG, you don't drive with the rpm higher than 2500 rpm, no need to increase intake flow at less than half the max flowrate.

Lot of wishful thinking that engine is breather easier. The throttle plate restricts the "breathing" in any situation except wide open throttle.

 

Not a well known member, but I do read a lot of these threads. I removed the secondary charcoal filter and replaced the paper filter with a dry flow filter. To reset the computer, I unplugged the negative battery cable for about 30 minutes, hooked it back up, idled for 5 minutes then went for a "drive". Hammered the throttle and wow, I certainly heard and felt a difference. Have now had 3 days to drive it and my initial impression is a much better idle, quicker throttle. I have a 2015 TRD 4 x 4 - V6. Certainly not needing as much throttle to maintain speed, so IDK, IMO it has improved performance so far. BTW, I kept the filter just in case.

UPDATE 6/21:

Has significantly reduced idle noise and vibration, no hesitation or groaning from a stop. Just hitting 1/3 tank consumed and I drive 25 miles/day give or take - this is since filling up on 6/15. For me that is an improvement since I usually fill up every 10 to 14 days it seems.

I wonder, if those who are not seeing any gains/difference, try resetting the ECU ?

 

I have taken pretty extensive mileage data over the last two years. I have a K&N Drop in filter. I plan on removing this and I will report back.

 

You still in the SA area OP? I live just outside of kerrville

 

Maybe this item is something I should try removing from my truck...LEAD FOOT attachment