Air Intake Modification

[Gunslinger]

I'm perplexed as well.

George I don't recall seeing yours, but if the K&N is installed inside the Donaldson housing you will get the advantage of the pre cleaner and water protection.  The K&N filter is probably a performance match to the Donaldson Oil bath.  It may also have a bit lower restriction which may have provided a bit better air flow for you on that hill.

Tom, by the looks of your set up it appears that the K&N will be doing all of the air filtration.  At least until it dirties up enough to equalize the restriction between the Donaldson and the K&N.  Once that occurs the two air cleaners will balance the air flow between them.  But as stated not much water protection, I'm not sure that's a problem if you don't drive on rainy days.

If you want to have some technical fun , you can buy a water Manometer and plug it into the main air duct after the Donaldson and then again after the K&N in Tom's set up.  That way you can measure the restriction in both set ups.  Just a thought.

Gun

[aboyandhisdog]

I was afraid my photo would be confusing.  The two air filters are not connected in-line as it appears.  There is a cap over the Donaldson outlet which dead ends up against the end of the new filter.  So I only have the new filter working, but I can swap out the new filter with the rubber "joiner" between the cross tube and the Donaldson in about a minute if I need to have it looking right for some reason.  I just didn't want to have to take the Donaldson off - it looks cool!

Honestly, I don't know if I'll see improved performance or not from the engine under severe load, but it does seem like there should be less "resistance" in the whole air intake which may let air into the engine easier.  I may or may not notice an improvement.

But...I DO feel like I will have every bit of air that enters the engine filtered!  I have been doubtful of this in the past.  After a year of driving and in some dusty conditions, I have had almost no dirt in the oil in the Donaldson.  And my Blackstone oil tests have indicated high levels of silicon (dirt) in my engine oil over the years.  A couple of years ago I modified the Donaldson to accept a paper cartridge filter and, while it seemed to filter better (from blowing the dust out) I can't say it was appreciably better than the Donaldson. 

With the new K&N style (actually an AirAid) I know for certain that ANY air that gets into this engine HAS to be going through that filter.  And yesterday I got my new pre-filter too which should keep out any splash from the tires or the fan.  Will be very interested to see what my oil test shows in the way of dirt a year from now.

[Gunslinger]

Thanks Tom,
I would be very interested in hearing more about the oil analysis data from the new filter.  That is really cool that your doing that.

Gun

[MikeB]

Not sure how effective a stock air filter is, how much dirt it allows past. But with the K&N style filters they flow better and get more air into the motor because they have a less porous filter element, meaning they allow more dirt into the motor. The pre filter wrap helps with this but I�m always worried about the fine particulate that gets past. I�m being a little hypocritical because I run a K&N on my M38 but only. Cause it is the only filter I could cramp into the very limited space left over from the engine swap.

It would be interesting to see the before and after oil analysis.

[mtnman37879]

Good write up in Hemmings Motor News about air filters. 

https://www.hemmings.com/magazine/hcc/2012/05/Breathing-Easy/3711731.html

[aboyandhisdog]

That is an interesting write up in Hemmings, Patrick.

MikeB, do you have a source of that graph?  The K&N and the AFE filters are very similar yet seem to vary considerably in performance.  I have a K&N in my Passat, and AFE in my Tacoma, and now an Airaid in my Willys.  I couldn't find performance data on the Airaid website so sent them an email requesting such.  Maybe I'll hear back, maybe I won't.  Will post performance data if I can find it!  It seems like there would be a lot of filter performance data out there, but I'm watching football today!

[Gunslinger]

Just a couple of thoughts,

When I was working at Donaldson we tested the K&N filters for performance against fine dust, we were in the business of protecting off road diesel engines so the interpretations were skewed that way.  Most of the engineers agreed that the K&N style filters were not up to that job, but what is that Job?

- Modern Diesel engines will be damaged by dust particles over 2 micron in diameter, so its not just the volume of dust that passes the filter but its size as well.

- Modern gas engines will tolerate dust particles up to 5 microns in diameter.  Much larger particles because the tolerances in the engines are less stringent.

The original oil bath filter on the Jeeps is the same in concept and design as the one that Donaldson put on the M4 Sherman tank during the North Africa campaign of WW2, to solve a problem with dusted engines.

I was able to find a performance book at NAPA for K&N filters, I checked the data for my 97 Cherokee sport, it showed that I could expect a a 10 HP performance improvement at 6000 rpm.  Much less at lower rpm.  I have not seen that book recently, it may still be available from K&N or NAPA.

If these pleated filters do actually perform as good as the oil bath, then they should not cause a problem for the engine as I would suspect the L134 is probably more dust tolerant than newer gas engines.  I would want to protect it from rain and damage.  Keep in mind if you look closely at the housing and mounting of the OEM Oil bath you will see how the the air must go through a treacherous path prior to entering the air cleaner, this is to shed heavy dust and rain particles, once inside the air cleaner the air makes a 90 degree turn, goes straight down and then reverses course 180 degrees to get to the mesh screen, again methodology to eliminate dirt using gravimetrical energy.

No conclusions, Just the ramblings of an old guy.

[MikeB]

That is an interesting write up in Hemmings, Patrick.

MikeB, do you have a source of that graph?� The K&N and the AFE filters are very similar yet seem to vary considerably in performance.� I have a K&N in my Passat, and AFE in my Tacoma, and now an Airaid in my Willys.� I couldn't find performance data on the Airaid website so sent them an email requesting such.� Maybe I'll hear back, maybe I won't.� Will post performance data if I can find it!� It seems like there would be a lot of filter performance data out there, but I'm watching football today!

Sorry been busy, the original article came from consumer reports and was reposted in a diesel performance magazine, it is about ten years old.
On modern cars with the tighter tolerances they are more susceptible to damage from �dusting� which is allowing fine particulate into the engine. And I have a more modern motor in my Willys (only 29 years old, compared to the 60 year old originals)� something I forgot to take into account when I posted my response. The K&N style filter should do no more harm than a stock oil bath, as long as you don�t use a cheap knock off with a substandard filter media.  When you think about it the original motors were built to be used in the worst possible environment with minimal maintenance.

I would still be very interested to see the oil analysis of a stock air filter set up us an K&N style.

[aboyandhisdog]

Hi Mike,   this pdf may or may not come through but I'll give it a shot.  The results from fall 2016 were on the Donaldson oil bath, and the 2017 and 2018 results were on the Donaldson but which I had converted to a paper filter.  I can't say for sure that I had a really good seal after converting to paper so my dirt #'s may be high for that reason.  Anyway, I just put on the AirAid this month when I changed the oil and I am now certain that I have a very good seal and that ALL of the air getting into this engine is being filtered.  I will know more in a year when I test again. 

To the best of my knowledge, the things that reflect "dirt" getting in (and air filter performance) are silicon and insolubles.   Important to note that silicon #'s can also be high if the engine had work done and a silicon RTV or something similar had been used.  Like if you use it on an oil pan gasket or something.

[mtnman37879]

Ya know, those oil type filters keep the water out. Dirt causes premature wear, Water causes immediate damage! Driving in a creek bed with a few inches of water gets the inside of your hood wet...