The way I read it, he said he saw it pull down more, not less, after he oiled it. He said his filtration was good then, meaning it was filtering the dirt out, but the filter minder went to 60%.

 

Exactly..so vacuum must have increased to pull it down. The idea that venturi vacuum pulled it down due to increased air flow doesn't work when the minder showed less with less oil.

 

by doug
Bernoulli equation for horizontal air flow:

P1 + ½ñV12 = P2 + ½ ñV22
So P2 – P1 = ½ñV12 - ½ ñV22 But V2 = 8.602V1 so:
P2 – P1 = ½ñV12 – ½ñ(8.602V1)2 = ½ñV12 – ½ñ*74V12 = ½ñV12(1-74)
P2 – P1 = -36.5ñV12 .
P2 – P1 = (-36.5)(1.3kg/M3)(16.81 M2/s2)
P2 – P1 = (-797.63)(kg/M3)(M2/s2) = -797.63 (kg*M/S2) / M2 which is -797.63 N/M2
P2 – P1 = -797.63 Pa = .1157 psi = 3.2 inches of water


I just opened a new bottle of aspirin if you need some.

 

True. On initial install, the minder didn't move enough to notice. Not until oiled to the point that I stopped seeing dust in my intake tube did the minder pull all the way down.

100 Proof
Do us a favor and check your tube after a couple hundred miles and let us know what you see. If your results are like mine, both inside bends will collect dust. It is very dusty here at times, so you may need a few more miles before enough collects to see it. Lets hope that you don't though.

The minder still pulls all the way down on hard runs, but I haven't had any dust in my intake tube for the last 1,500 miles. I just had my first oil analysis done with 3,000 miles on this batch. Second oil change, but first analysis. I used Blackstone Lab. My silicone level was 12ppm. They said it was higher than they would expect for this engine with only 6,000 miles on it, considering break-in, but it was on the high side of "within limits." Anyone here have an analysis done at a similar interval to compare?

 

I'm not sure I get it completely either. My filter minder with stock filter and stock box used to pull down to 30% when the filter was new. Earlier someone posted that they measured this vacuum as 10" water.

If the AFE drops 1.5" water and the Bernoulli effect is 3.2" water then it should only be at 4.7" water total which would pull the filter minder to less than 30%, not 60%.

 

We will forever chase our tails if we try to pin calibration marks onto the factory filter minder. I don't even think its wise to compare one truck to another. the device appears so crude that it shouldn't be trusted as a measurement device -- that is an instrument that reports a meaningful number.

what it can be used for is comparative purposes on the same truck with different air intakes. All that ugly math only shows that on the same truck, the filter minder should pull down about the same amount, or maybe a bit more, with the AFE/TT combo IF the AFE restriction is as advertized. we haven't validated that last part yet.

What we still don't understand is AK's results showing that it appears to take an over-oiled filter condition (well, more heavily oiled than factory new) to prevent dust on his intake, and even when he oils more than the factory, he gets silica levels in the teens at 6,000 miles. thats terrible. With those results, AK, I'd be back on the horn with AFE asking for another filter. that just doesn't sound right, and it certainly is out of whack with both their test results and their expectations. You should be seeing silica levels in the low single digits with the PG-7 at 6,000 miles from what I've been told. not only is the filter claimed to be equal to factory filtration, it doesn't suck dust right off of your rt. front tire

 

I agree with doug, you are in line for a replacement AK, The amount of usage you have been more than helpful in this quest and I would think AFE would be glad to keep you as a happy customer & a source of product t&d for this forum. Keep us informed..

 

If I may, I'd like to piggyback here. I'm a second Gen guy who still runs the stock filter.

This thread has lost sight of the thought processes that should (imho) determine filter selection. So may I humbly submit my suggestion for filter selection:

1) know the horsepower you at or want to be at.

2) Know how much air is required to support that much horsepower

3) add a fudge factor to be safe-- maybe 5%-10%?

4) find a filter that will flow that much air with maximum filtration and minimum restriction.

On restriction, you have to be careful with how you refer to to inches of water. Specifically, you are talking about a PRESSURE DIFFERENTIAL between the atmosphere (before the filter) and the intake system (after the filter).

Furthermore, this differential is expressed as the difference in height between two water columns, as illustrated here.

A perfect vacuum would raise a column of water 407 inches!! This assumes atmospheric pressure (14.7psi).

So when you talk about a "restriction of 10 inches", that restriction represents a pressure different of less than 3%.


Please remember that when discussing these aspects, you HAVE TO KEEP IT IN CONTEXT. For example, voltage tells you little without resistance or current. Pressure tells you little without volume or flow.

Anyone remember the "pumps, lines, what not" tdr thread?

The most common source of confusion is that pressure can be EITHER the force, OR THE RESTRICTION TO FLOW. In the fuel flow case, people were confused about whether more fuel pressure meant less fuel flow or more fuel flow. Which is it?

It's BOTH-- depending. There are three items to consider here: the fluid that's flowing, the force that's making it flow, and the opposing force that resists that flow. So when you see your fuel pressure drop when you get on the pedal, it's because you've lowered the opposing force. Thus, more flow at lower pressure, not FROM lower pressure, but AT lower pressure.

Now you take your truck and install a wildcat max flow system which supposedly allows more flow and you see MORE pressure! What gives? You see more pressure because the restrictions upstream have been reduced, allowing more pump pressure to reach the point where your gauge sees it.

A pressure reading must ALWAYS be related to the "opposing force" (restriction) and the assisting force (like fuel psi, or atmospheric pressure), and it must always be remembered WHERE in the system you're measureing pressure....

OK, so what about air filters? What even causes air to flow?

Air flows because of differential pressure. "Nature abhors a vacuum" is how it's often stated. Namely, nature always tries to balance forces. So, if you have an area of low pressure and one of high pressure, nature tries to balance those forces by flowing air from one to the other. That's what causes wind.

In your truck, the low pressure is caused by the centrifugal compressor on your turbocharger. So nature tries to "fill" that vacuum by flowing air into the low pressure area.

The force that pushes that air towards the turbo is atmospheric pressure-- 14.7 psi at sea level. This pressure is the result of the weight of all the air above us. That's why there's less pressure at altitude: there's less air above you, so less weight of air.

For maximum efficiency, we want this air to be filtered adequately but with as little restriction as possible. In other words, we want to see as much of that 14.7 psi after the filter as possible.

Now let's embark on a little logic exercise. If I have a tube of 3" sectional area, and I have three tubes of 1" sectional area each, which arrangement flows more air?

We agree that they would flow the same. They have the same total sectional area and offer the same "opposing force"-- restriction, resistance to flow, etc.

But do they filter the same? NO NO NO. The three tubes will filter out particles larger than 1", while the 3" sectional tube will only filter out particles larger than 3". Granted these are more like landscaping stones than particles, but you get the idea.

Now, what if I had 300 tubes of .01" sectional area? Still the same effective flow area, but now it will "filter" out particles bigger than .01 inches...

You can tell where this is going. As the flow channels get smaller, we need more of them to preserve flow. What else does this logic exercise tell us?

Restriction and Filtration are NOT correlated as some peope think.

We can realize this is true if we recognize that the relationship between restriction and filtration is NOT cause and effect. They are BOTH effects of a common cause- filter design or cleanliness. A dirty filter will cause both the restriction, AND an increase in filtration. But the restriction did NOT "cause" the increased filtration!

So when someone tries to say that one filter flows better than another because there's more of a pressure drop, you can confidently tell them they are not thinking logically, because one can reproduce that restriction with NO FILTRATION just with you hand over the orifice.

The other conclusion you can draw is that if you want both filtration and airflow, then you're going to need a very large filter. Because we're trying to filter things out on the order of microns (for the record, that's one MILLIONTH of an meter, or one thousandth of a millimeter), then we need a LOT of little"flow tubes" to allow for the high airflow will maintaining filtration.

That's the logic part of it-- what about filter design theory?

(continued next post)

 

What do we want a filter to do? We simply want it separate particles of a known size from air particles of another known size (molecules). We want it to store the particles it removes. We want it to do this without robbing the incoming air flow of its energy.

The biggest theory of filtration is what I'll call the "sieve theory." This is what most filters use, whether they are paper, screen , or whatever. This is a mechanical means of particle separation based on the size of the orifice of the separating media. We all understand this.

The next one is what I'll call the "flypaper theory". The oiled-gauze filters use this in addition to the sieve theory. This theory relies on particles sticking to something that the air won't stick to. This is the oil in the oiled filter, whether it's gauze or foam.

The last theory I know of (since I'm just making all this up as I go) is the "centrifuge theory". This method of filtration relies on the fact that the particles you are trying to remove have much more mass than the air does. So if you can find a way to make the air flow in a high-speed circle, then the dirt will be flung out and the air alone will remain in the center. This is how the Dyson vacuum cleaners work if you've ever seen them.

The most effective filter would combine all three of these, imho.


Paper gives you sieve effect, but no stickiness and very little if any centrifugal effect.

Oiled gauze gives you the seive effect AND the stickiness, but you don't get much, if any centrifugal effect.

Oiled foam, however, gives you all three. You get the sieve effect, the stickiness of the oil, AND you get a lot more centrifugal effect because there's no straight shot through the filter-- the airflow has to make a lot of turns that fling the dirt into the sticky parts.

So, imho oiled foam is the best purely from the perspective of filtering. I highly doubt they would flow the best.

BUT! There is an antidote for a restrictive media-- SIZE! Paper is fairly restrictive, but people still see improvements when they switch to the BHAF.

So the ultimate solution might be a HHAF-- that would be the Huge Honkin' Air Filter. It's a lot bigger than a BHAF even

If someone is absolutely concerned about engine longevity, then imho they should favor filtration over flow. But we've seen these aren't mutually exclusive.

When is someone going to make the right air filter for us?

I hope this contributed something to the discussion....

Justin

 

Dam* this stuff is GOOD..
My Brain hurts this early in the morning

 

Hohn, you're right. We need to re-state our design objective in one place. We've discussed most but all points, and never really consolidated the design in one place. it turns out that the design objective is precise and clear:

1. We have specified flow without specifying HP, simply because flow depends on engine displacement, rpm and boost.

2. We found that our intake needs to flow at 600 CFM

3. We've had some discussion over minimum restriction and you are right. We're having to debunk some of the recommendations of the paper filter mfgs who have innaprpriately generalized the restriction=filtration rule of thumb used on their own filter products. I think you did a good job of that.

4. so indeed we are targeting the minimum restriction possible that provides the required flow and filtration.

5. Our filtration spec is to meet or exceed the factory system. Recently we have found this to be 99.56% efficiency per SAE J726 "AC fine dust" test.

I note that we tend to consider the effect of elevation on horsepower, but we don't consider the effect of air filter restriction. We use the rule of thumb that, due to volumetric efficiency, an engine will loose approximately 3% of its HP for every 1000 ft of elevation -- because air pressure decreases at about 3% per 1000 ft. But if the air filter itself contributes a similar reduction in air pressure, we tend to ignore that.

most of this problem, in my opinion, comes from generalizing from various engine and air filter mfgs who have specific design goals that may not match ours.

Anyway, in each of the following cases, the absolute air pressure seen by the turbocharger's compressor wheel is the same:

1. you keep the same air filter, but move up 1000 ft in elevation
2. you stay at the same elevation, but you put in an air filter with 3% more restriction.

Oh, and mixed in with this discussion is an effort to understand the behavior of the AFE oiled paper filter as a possible candidate to meet the design requirements outlined above. So we talk about filter minders pulling down, and the dust in AK's intake tube...

 

Done. 300+ miles since the install, including about 10 miles following other vehicles on a dirt road. Checked and it is clean. I inspected my filter again: even, golden color all the way around.

I'm with those that think you need a new filter.

100 Proof

 

OK, I did this. I took a short length (about a foot) of clear PVC tubing that I had laying around in my garage. I think it is 1/4" or 3/8". I pushed it into the bung for the filter minder in the AFE setup, a "neat" fit. I ran the other end into the filter, hanging loose near the middle. In this configuration the end is out of the flow area and the minder should be measuring pressure drop only with no venturi effect, like the stock filter minder setup.

I then took it out on the road and made several WOT throttle accelerations, holding it to 3,400 RPMs before shifting in 2nd, 3rd, and 4th gears. This is a much more aggresive run than when I first noticed it down to 30% right after the install. (BTW, it was down to 60%+ after I pulled my trailer around for the weekend.) I then pulled over and popped the hood for a look-see.

Results: Filter minder NOT pulled down at all! PG-7 users, WE WIN!!

I hope someone else will repeat this experiment to verify my results.

100 Proof

 

With the known effect of the venturi vacuum effect for some I wonder when if AFE will address this issue or if they would just remove the filter minder from ther set up?
2) I don't seem to suffer with the filter minder venturi effect pulling the indicator to even register any movement at wot with usage running into 2000 mi and I have played the pedal heavy... . Does this item even work ??

3) As show by 100 proofs modifaction it would seem to me that AFE would be able to provide a correct location in the initial set up for the filter minder in the first place, poor engineering or just a lack of engineering in the design of the unit?
4) I believe that AFE should address these issuse's or consult with Honh, AK, Doug,(ect,ect, the list goes on) in product devolopement ...
I will wait and see

 

Remember, I have the early minder with the wimpy spring. If you have the later one, your results SHOULD be different.

100 Proof