Hello, from San Diego.......
I notice that my stock air cleaner clean / flow button will sometimes go down to 50%, so I reset it. Is my AEM brute force intake w/dry filter not flowing enough. Or should I even use the air cleaner button or worry?
Thanks ........

That air filter reminder contraption is fairly simplistic: the more resistance it has the further the flow meter moves towards changing it. It's not too reliable, just a visible indicator for folks to check the status of the air cleaner. Sometimes after some very high RPM pulls my filter minder would be about 50%, even with a clean OEM filter, go figure? :confused:

If the filter setup you are running has severe airflow restriction you probably should go back to the OEM filter, it appears to provide better filtering and airflow than most. :confused: My .02 cents worth. JJ :)

Duramax4play,

You can't feed a diesel enough air, period. I have seen on the Dodge sites where they are having lower boost numbers after installing the AEM Dryflow filter set ups, even when comparing to the stock paper filters! That tells me they are pretty restrictive, which makes sense, to stop the dirt they have to be, and oiled filter (like and AFE Pro Guard 7) uses the tack properties of the oil to catch the dirt, if you don't have some type of tack element then you have to rely on smaller and smaller openings to catch the dirt which will result in restriction etc.

Lots of members here do not feel that a system like and AFE PG7 is beneficial to the 6.6, it is but do NOT buy it for HP, but it for quicker spool up on the turbo, lower EGT's and in increase BTU use of the fuel you are burning! If you have any questions call us, we'll be glad to help.

Mark @ DPPI

Hello, from San Diego.......
I notice that my stock air cleaner clean / flow button will sometimes go down to 50%, so I reset it. Is my AEM brute force intake w/dry filter not flowing enough. Or should I even use the air cleaner button or worry?
Thanks ........

The filter minder is a little vacuum gauge that will latch (get stuck on purpose) at the highest vacuum reading it has seen since being reset.

A filter will get more restrictive as it gets dirty. When you go full throttle airflow is at a maximum, and so is the pressure drop of the filter. The filter minder is calibrated to start moving down the scale when the filter is dirty enough and restricted enough to need replacement.

If your "high performance" filter is tripping the filter minder with a new or clean filter element, then your filter has as much restriction as a completely dirty stock paper element...and is costing you power and economy.

cit1991,

Not entirely true, we have been seening this for a long time especially in the Fords, the Duramax is starting as the HP has gone up as well though. The "quality" of the air minder is minimal at best, especially when compared to the ones used on Class 8 vehicles. What you are seeing is the velocity of the increased air volume (CFM) causing the minder to suck down. It's not restriction as if you had a more restrictive air flow the EGT would rise not fall as they do when you add an intake system.

Mark @ DPPI

im having the same problem,i just posted the question,bottom line ,has anyone done a real dyno test w/ these air intakes compaired to the stock air box?are the intake temps as important as they are in the gas motors,cooler the better?

Mark, I respectfully disagree with you on this one.

The OEM filterminder is a cheapo unit, sure, but it's going to measure vacuum just like any other fancier gauge. It has zero to do with velocity (and in fact could never measure velocity) and all to do with vacuum in the inlet. It's a spring-loaded diaphragm gauge.

Anyone wanting to see how it works, just take your filter off and stick your hand in the tube (I have the AFE) while idling the engine, and about the time you get your hand all the way in, it will start sucking and the filter minder will depress. You would see the exact same thing if you put a big u-tube manometer on it.

FWIW, after putting the A5k on my truck and doing some big tune launches, it sucked it down to 100%. So I took the filter off and tried it again. Same thing, maybe only 80%....which means I'm moving enough CFM that the tube itself is not big enough - which makes some sense, the A5k inlet is 5" with the MWE shroud.

I don't think it's causing me a significant horsepower loss, but it's enough that I'm going to work on it. And it's also no surprise why some of the boots collapse on the A5k kits; the vacuum can be surprisingly strong even at idle. I bet it would be pretty wicked at WOT and 50+psi boost!

Actually, you are both correct. Too funny.

Yes - The filterminder is a spring-loaded diaphragm that functions based on spring pressure versus air pressure differential against the diaphragm. One key note is that the spring is calibrated to work with the OEM system and will not operate correctly with most aftermarket filters and/or intakes.

Even though the CFM level is equal, any restriction at the filter or inlet will cause the incoming air to increase in velocity. Air moving down the tube AND/OR over an opening in the tube will create a pressure drop on the opposite side. (Read: Vacuum). As the filter loads over time (restriction), air velocity inside the intake also increases.

The pressure drop (vacuum) was caused from the filter restriction level increasing. That is because the restriction from the filter speeds up the incoming air (velocity) and gives you your pressure drop (vacuum).


It's difficult for me to explain this tonight for some reason, so I'll probably have to revisit this post tomorrow and clean it up.

Sorry guys!

Well, OK, fine. Regardless of the velocity change, the existence of vacuum is a direct indication of restriction, which acts directly against what we're trying to do: flow as much CFM as possible.

If you look at the filterminder as a differential pressure gauge and the filter as an orifice, then you could calculate the CFM flow using all the standard engineering equations. You could probably get linear velocity by dividing that by the cross sectional area. But who gives a crap about velocity? When I stick my hand in, the air moving by my hand is dang quick, sure, but I still have a big fat restriction!

I agree that the horsepower loss my be minimal, but restriction isn't helping anything and I intend to do something about it.

Even if it's only making me sleep better at night ):h

911sTarga,

Yeah I know what you mean to know what is happening is one thing to be able to type it is another. My history on this is learned the hard way on the Ford Powerstroke Sites. A few years ago any intake that was added immediately caused the minder to bottom out, now we all knew the intake flowed waaay more air than stock but then if the minder worked on vacuum and the new inatke flowed more what was going on. I got the guys at AFE to explain it and it came down to velocity was creating a vacuum past the minder vs before it and caused the restriction reading at the minder. In actuallity it wasn't restriction it was velocity etc. Therby my opinion of the performance of the minders is very poor. Get one on a class 8 truck and they work great, but they are waaay more accurate etc too! Hope this makes the waters only slightly muddly!!!

Mark @ DPPI

Teah I've got one of the oiless filters and keep setting the low boost code. I've called AEM several times and can never talk to one of the techs. They are always "away from the desk" left messages and haven't heard back. Anyone else have bad service with AEM? What should I do? (besides put the stock box back on) Although I am very close):h

i had the same problem,never called back.i will never use another aem product in my shop after that.like i said before,aem is a rice car co. and the service is lacking.my filter gauge was bottoming out too,just wanted info on that and no call back.losers.i will buy a name brand for my trucks,next time.

A while back, when I had a BMW, I was at Dinan for a tour, and asked about K&N filters. They told me how they are poor filters (which I knew). Concerning performance, they take the stock filter and partially cover it with strips of duct-tape, one strip at a time, and dyno the engine in between. They look for a measurable drop in power.

In the case of my car, they had to get the filter half covered before seeing any measurable power loss. So they said the stock paper filter was fine, and any less restrictive filter would not help.

That's the right way to test for a filter.

To say that a restriction causes pressure drop is true. To say that a drop in pressure causes in an increase in velocity is true. To say that an increase in velocity causes pressure drop is not true. The causality is the other way around. It's like saying an increase in power causes the gas pedal to go down...they're related, but the casuality is the other way.

The engine at constant boost and RPM (and intercooler temp, etc.) is an air pump at a (more or less) fixed SCFM. A restriction will increase the intake ACFM (due to lower density), but not SCFM, which is what the engine needs.

An untripped filter minder indicates such a low vacuum (probably <0.1 psi or so), that I don't see how any further reduction in restriction would add anything measurable.

Now, a new intake tube (smoother) might help, but the stock filter element itself has plenty of capacity at a de-minimis pressure drop.

Maybe if we could see some numbers (EGT, rwhp, vane position, boost), with only the filter element changed?

As you have pobably surmised, I'd like to see someone make a new (smoothed) intake tube (only), from MAF to turbo.