Curiosity got the better of me

[widman]

I swore I would not look at my air filter until the restriction monitor said to, but today, after 15 months and 23,000 km I decided to take a peek. The manual says "inspect" every 20,000 km.
A visual inspection would say it is terrible, but it has no restriction yet. This is the original Mopar filter on my 2009 Grand Cherokee, and there is no dust on the intake or top half of the housing.


Sort of the reverse of what I found when on my Hi Lux at 20,000 km when the indicator said it needed changing, though it looked clean but was passing dust.

I think the restriction gauges should be standard equip.

 

[beast3300]

Those indicators are not very good (obviously). Good thing you checked!!!! I assume you're getting a new filter.

 

[Nayov]

Please tell me you replaced the top filter, restriction gauge be [censored]!

 

[XS650]

Originally Posted By: Nayov
Please tell me you replaced the top filter, restriction gauge be [censored]!


That would kind of defeat the purpose of the gauge.

If there is any doubt it should be checked. You can Y one with a known good vacuum gauge and see how much vacuum it takes to get a restricted filter indication. Should be someplace between 1 and somethng less than 2 inches of mercury.

 

[Dieseldoctor]

The assumption is that a dirty air filter is bad.. the absolute opposite is true actually the more dirt a filter collects the better it filters. Also the myth that a dirty filter will reduce your mpg is also proven false given the modern feedback fuel systems. I always use a restriction gauge on my vehicles i was suprized to find how long a typical air filter would go w/o replacement if u buy good quality filters u can go easily 50K miles.

I figure everyone will reject this so heres gov testing about this very subject http://www.fueleconomy.gov/feg/pdfs/Air_Filter_Effects_02_26_2009.pdf

 

[Colt45ws]

This illustrates pretty well the reason for getting one of those gauges, IMO. A slightly informed person would probably replace the first one and keep the second (or worse, blow it out)...

 

[widman]

Actually in the morning I'm going to put a variable gauge on it to see what the restriction is. The variable runs 10" to 30", whereas the fixed one is 25"

Car runs fine, same mileage as always.

 

[Nayov]

Originally Posted By: XS650
Originally Posted By: Nayov
Please tell me you replaced the top filter, restriction gauge be [censored]!


That would kind of defeat the purpose of the gauge.

.

So are you saying that the blackened filter is OK to use becasue the gauge says it's still good?

 

[Hokiefyd]

Despite the photos, that "blackened" filter is still completely serviceable. Until you see a significant pressure drop across the filter (which would be indicated by the gauge), the filter is still doing its job without any real effect on the engine. In fact, as others have said, a filter's efficiency generally increases as it begins to get dirty.

In theory, the point of maximum efficiency, from a filtering AND a performance standpoint, is the point at which the filter has accumulated enough dirt to JUST begin to show a pressure differential of 5-7 PSI (which is what those gauges are calibrated to I believe). If you re-read the first post, it states there is no restriction yet. Period. Filter's still just fine.

People change air filters WAY too often. Really.

 

[Colt45ws]

5-7psi does not sound right at all. If Im doing this correctly thats 166" of water. These gauges are calibrated for 20-25" of water from what Ive seen? Maybe you mean .5-.7psi?

 

[widman]

this is a 25" restriction gauge, which correlates to about 1 psi.

 

[Samilcar]

Originally Posted By: Nayov
[
So are you saying that the blackened filter is OK to use becasue the gauge says it's still good?


Why wouldn't it still be good? The gauge doesn't look at the color of the filter, it measures how much it's restricted. If the blackened filter flows the same as a new filter, it's good to go. The only difference would be that the blackened one would filter incoming air slightly better.

 

[ET16]

Originally Posted By: Colt45ws
This illustrates pretty well the reason for getting one of those gauges, IMO. A slightly informed person would probably replace the first one and keep the second (or worse, blow it out)...


Why would it be bad to blow out?

 

[widman]

The dirt is trapped in the fiber like a maize. You can't get it out without damaging the fiber. I have dozens of examples of oil analysis on my site where people have done that.

 

[Hokiefyd]

Originally Posted By: Colt45ws
5-7psi does not sound right at all. If Im doing this correctly thats 166" of water. These gauges are calibrated for 20-25" of water from what Ive seen? Maybe you mean .5-.7psi?


Yes, I probably did. Thanks for the correction. The point I was trying to make (and others [and you] made it as well), as long as the filter is not soiled to the point of restricting air flow, it's still good to go.

 

[SuperBusa]

Originally Posted By: Colt45ws
5-7psi does not sound right at all. If Im doing this correctly thats 166" of water. These gauges are calibrated for 20-25" of water from what Ive seen? Maybe you mean .5-.7psi?


Exactly ... 5 to 7 PSI drop is ridiculous. If it was 7 PSI drop, you'd only be getting 1/2 an atmosphere of pressure into the intake manifold at full throttle. 7 PSI pressure drop would basically cut the airflow into the engine by 1/2 and your power by 1/2. Not buying it.

 

[XS650]

Originally Posted By: Nayov
Originally Posted By: XS650
Originally Posted By: Nayov
Please tell me you replaced the top filter, restriction gauge be [censored]!


That would kind of defeat the purpose of the gauge.

.

So are you saying that the blackened filter is OK to use becasue the gauge says it's still good?


Yes, as long as the gauge is correct.

 

[widman]

That is the point of the gauge that reads what happens with the engine, rather than the eye that sees the surface. What sticks to the surface doesn't clog the fiber.

 

[Colt45ws]

Originally Posted By: widman
That is the point of the gauge that reads what happens with the engine, rather than the eye that sees the surface. What sticks to the surface doesn't clog the fiber.

Did you get around to putting a variable gauge on it?

 

[widman]

I have to figure out an adapter. the variable gauge has a threaded fitting that is narrower than the one that slides into the grommet on the fixed one. And just haven't had time.