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Sunlight test vs restriction gauge #4758348
05/16/18 12:00 AM
05/16/18 12:00 AM
Joined: Mar 2008
Posts: 607
A Warm place to live in
berniedd Offline OP
berniedd  Offline OP
Joined: Mar 2008
Posts: 607
A Warm place to live in
Yesterday I changed my Ford's paper air filter with an original Motorcraft. I noted that the old one was dirty grey on the outside pleats (but no clumps of fluff) and it did fail the sunlight test (no light seen through the pleats). I don't have a restriction gauge on the car and wondered that if I did have one, what reading would I expect to get?

Re: Sunlight test vs restriction gauge [Re: berniedd] #4758365
05/16/18 01:26 AM
05/16/18 01:26 AM
Joined: Sep 2010
Posts: 7,485
S California
OneEyeJack Offline
OneEyeJack  Offline
Joined: Sep 2010
Posts: 7,485
S California
The airflow delta gauges I've used have calibrated markings. When the needle is in the red, do something. If not, do nothing.

Re: Sunlight test vs restriction gauge [Re: berniedd] #4758408
05/16/18 05:35 AM
05/16/18 05:35 AM
Joined: Oct 2012
Posts: 4,630
Taiwan
Ducked Offline
Ducked  Offline
Joined: Oct 2012
Posts: 4,630
Taiwan
General guideline I've seen, IIRC. is 10 inches of water in excess of a new filter.

I rigged a water manometer and was getting less than an inch before I added some extra restriction to the used filter, which is a bit of a puzzle unless the filter has a hole in it.

Don't really see what there is to go wrong with a water manometer.

Re: Sunlight test vs restriction gauge [Re: berniedd] #4758436
05/16/18 06:33 AM
05/16/18 06:33 AM
Joined: Mar 2008
Posts: 607
A Warm place to live in
berniedd Offline OP
berniedd  Offline OP
Joined: Mar 2008
Posts: 607
A Warm place to live in
No, no, guys. What I wanted to know was, given that the filter failed the "sunlight seen through the pleats" test, what do you think the amount of restriction was. Aka, what do you think the delta P across the filter would have been. Your answers will help me decide in the future if I should change the filter earlier or later than the 13,000 miles it took to get that amount of trapped dirt. I don't have a restriction gauge to help me out. Thanks again.

Re: Sunlight test vs restriction gauge [Re: berniedd] #4758455
05/16/18 06:52 AM
05/16/18 06:52 AM
Joined: Oct 2012
Posts: 4,630
Taiwan
Ducked Offline
Ducked  Offline
Joined: Oct 2012
Posts: 4,630
Taiwan
Originally Posted By: berniedd
No, no, guys. What I wanted to know was, given that the filter failed the "sunlight seen through the pleats" test, what do you think the amount of restriction was. Aka, what do you think the delta P across the filter would have been. Your answers will help me decide in the future if I should change the filter earlier or later than the 13,000 miles it took to get that amount of trapped dirt. I don't have a restriction gauge to help me out. Thanks again.


Don't know.

I doubt the "sunlight test" has ever been calibrated, so perhaps no one else does either. It might be difficult to standardise since sunlight intensity varies from 120,000 lux (bright day) to 40 lux (full overcast)

If you want to know your filter restriction, why not make yourself a water manometer?

(Apart from mine maybe mysteriously not working, that is)

Last edited by Ducked; 05/16/18 06:56 AM.
Re: Sunlight test vs restriction gauge [Re: OneEyeJack] #4758462
05/16/18 06:58 AM
05/16/18 06:58 AM
Joined: Oct 2012
Posts: 4,630
Taiwan
Ducked Offline
Ducked  Offline
Joined: Oct 2012
Posts: 4,630
Taiwan
Originally Posted By: OneEyeJack
The airflow delta gauges I've used have calibrated markings. When the needle is in the red, do something. If not, do nothing.


Think an "airflow delta gauge" is/would be something else. My understanding is a restriction gauge measures pressure differential, not flow.

Re: Sunlight test vs restriction gauge [Re: berniedd] #4758559
05/16/18 09:02 AM
05/16/18 09:02 AM
Joined: Aug 2005
Posts: 4,563
NW Ohio
Jim Allen Offline
Jim Allen  Offline
Joined: Aug 2005
Posts: 4,563
NW Ohio
The "sunlight" test is so subjective as to be essentially useless IMO but I would be interested if someone were to test it against instrumentation to "see" if it works (pun intended (: < ).

That said, based on what I have "seen" (pun intended again) a filter has to be pretty obviously nasty to show major restriction. I have had gauges on my rigs for the past, 10 years or so, and still haven't had to change a filter on the roadgoing vehicles. The Farm equipment is a little different but the only one that showed any significant restriction within a year was in my John Deere combine after a season. If you saw the dust in which a combine operates, you'd know why, and know that's equivalent to about 150,000 miles of dirt exposure (or more IME) for a passenger car. It was literally caked with dirt BUT was still only showing yellow (don't recall the actual number, but near 10").

The filter in the Honda Accord is about 11 years old at this point (installed in 2007) and has just under 54K miles on it now and the gauge has not moved. I've looked at it once since I installed the gauge in 2008 (tripping at each service and doing a WOT to reset) and there was some junk but nothing particularly serious (I vacuumed it off). Bear in mind I live in farm country down a gravel lane that's a half mile long, so my service is probably more severe than some-o-ya "city folk" (: < ).

A few years back when testing the intake system on the late, great '05 F150 on a flowbench, we tested some throwaway filters I had collected from a nearby Ford dealer. Even the nasty ones were not all that far off a new filter.

Along the same lines, there is a white paper on the web (I printed it out but didn't bookmark it) by Marius Toma from 2015 where the University of Bucharest tested about 90 filters collected from the dealer for a popular brand of commercial Renault-powered vans. They recorded the miles at which the filters were collected... most of them changed at the factory interval. They used the intake system of the van to calibrate the restriction of a new filter and the built in restriction of the system and then began testing the collected filters. Turns out NONE of the of the collected filters exceeded the standard 10" restriction over a new filter, even one with 137,560 KM on it. Those changed at the factory interval were only 36% above the new filter for restriction and still 60% below maximum restriction. A similar test series to this done at another place and added chassis dyno testing to the equation and tested the most restricted filter (still below the point where replacement was indicated) and found the engine was generating virtually the same power as with a new filter (had not reached the restriction point yet where power was effected.. they noted the intake plumbing, not the filter, was most of the intake restriction).

And bear in mind that the first 10% of an air fitler's life is when it is the least efficient and most of the lifetime of contaminants that pass thru the filter do so in that first 10% of use. This is why you change the filter by restriction, not looks or an arbitrary interval that is calibrated to a worst case scenario (if you want to be generous) or to sell more filters (if you want to be cynical). Bottom line, changing your filters too early and too often is counter-productive to longer engine life. The intake system is THE major source of outside contamination into an engine, so IMO, it's the MOST IMPORTANT part of making an engine last. It also helps the oil and oil filter last longer due to less contamination inputs.

The variables are that some engines have a great deal of filter area so can go a good long time before restriction effects power output, and some have less area so those will be effected sooner. Again, the restriction gauge tells you when in every case and in every operational situation (cleaner air or dusty conditions).


Jim Allen
Keepin' the Good Old Days of Four Wheeling Alive
Re: Sunlight test vs restriction gauge [Re: Jim Allen] #4758673
05/16/18 10:58 AM
05/16/18 10:58 AM
Joined: Oct 2012
Posts: 4,630
Taiwan
Ducked Offline
Ducked  Offline
Joined: Oct 2012
Posts: 4,630
Taiwan
Originally Posted By: Jim Allen


That said, based on what I have "seen" (pun intended again) a filter has to be pretty obviously nasty to show major restriction......


Thanks' Maybe my monometer is working OK then.

Re: Sunlight test vs restriction gauge [Re: berniedd] #4758733
05/16/18 12:01 PM
05/16/18 12:01 PM
Joined: Aug 2003
Posts: 12,905
NE,Ohio
Rand Offline
Rand  Offline
Joined: Aug 2003
Posts: 12,905
NE,Ohio
engine air Filters can last 50000 or more miles if you dont live somewhere dusty.


2019 Jeep Cherokee Trailhawk 2.0T
Re: Sunlight test vs restriction gauge [Re: berniedd] #4758785
05/16/18 12:48 PM
05/16/18 12:48 PM
Joined: Dec 2015
Posts: 89
Pocatello, Idaho
compratio10_5 Offline
compratio10_5  Offline
Joined: Dec 2015
Posts: 89
Pocatello, Idaho
I confirm Jim Allen's post above. About 10 years ago, I finally caught on that dry air filter efficiency improves with use as long as the filter seals and air ducting downstream of the filter are air tight. I installed finder minder gauges on all my vehicles and relatives vehicles that I could convince. Since that time I have never changed an air filter on a vehicle driven primarily on paved roads, though some are about half way through the allowable restriction range after 100,000 miles. I check filters and hoses every few years just to be sure the seals are still good. The sunlight test is inconclusive, though I do use that test to check on the integrity of new filters to be sure that there are no tears, rips or holes. Thank You, Jim Allen for bringing the importance of air filters to our attention again.


It's not what you don't know that hurts, it's what you think you know that ain't so. Will Rogers
Re: Sunlight test vs restriction gauge [Re: berniedd] #4758787
05/16/18 12:50 PM
05/16/18 12:50 PM
Joined: Feb 2014
Posts: 593
Margate England
Claud Offline
Claud  Offline
Joined: Feb 2014
Posts: 593
Margate England
All the time the filter can pass enough cleaned air not to hamper performance it doesn't need changing.
I remember an instructor telling my class "A filter is working best just before it becomes to clogged to flow properly."

Claud.

Re: Sunlight test vs restriction gauge [Re: Rand] #4758852
05/16/18 02:00 PM
05/16/18 02:00 PM
Joined: Mar 2016
Posts: 1,425
Western S.C. since 1996
CR94 Offline
CR94  Offline
Joined: Mar 2016
Posts: 1,425
Western S.C. since 1996
Originally Posted By: Rand
engine air Filters can last 50000 or more miles if you dont live somewhere dusty.
Waayy more than that, easily. In deciding on their filter-change milage recommendation, manufacturers have to assume near-worst-case conditions, which don't apply to most owners. Besides, their dealers want to sell filters.


2011 Toyota Prius now at 92K
1981 Mazda GLC (323) retired at 606K
1972 Subaru DL retired at 190K
1954 Chevrolet retired at 121K
Re: Sunlight test vs restriction gauge [Re: berniedd] #4761150
05/18/18 03:21 PM
05/18/18 03:21 PM
Joined: Feb 2005
Posts: 1,771
Arizona
bulwnkl Offline
bulwnkl  Offline
Joined: Feb 2005
Posts: 1,771
Arizona
Any hypotheses as to why oil filters work the other way around? Data shows that they get _less_ efficient as they load with contaminants. Why do air filters not behave the same way?

Re: Sunlight test vs restriction gauge [Re: bulwnkl] #4761173
05/18/18 04:02 PM
05/18/18 04:02 PM
Joined: Mar 2016
Posts: 1,425
Western S.C. since 1996
CR94 Offline
CR94  Offline
Joined: Mar 2016
Posts: 1,425
Western S.C. since 1996
Originally Posted By: bulwnkl
Any hypotheses as to why oil filters work the other way around? Data shows that they get _less_ efficient as they load with contaminants. ...
Good question! I suspect one (not the only) reason is that oil filter testing continues to a much higher pressure drop across the media, so previously trapped particles are more likely to be forced through the media.


2011 Toyota Prius now at 92K
1981 Mazda GLC (323) retired at 606K
1972 Subaru DL retired at 190K
1954 Chevrolet retired at 121K
Re: Sunlight test vs restriction gauge [Re: bulwnkl] #4761653
05/19/18 06:39 AM
05/19/18 06:39 AM
Joined: Aug 2005
Posts: 4,563
NW Ohio
Jim Allen Offline
Jim Allen  Offline
Joined: Aug 2005
Posts: 4,563
NW Ohio
Originally Posted By: bulwnkl
Any hypotheses as to why oil filters work the other way around? Data shows that they get _less_ efficient as they load with contaminants. Why do air filters not behave the same way?


I don't know what data you are looking at, but that's simply not the case. The same sort of efficiency improvement occurs with an oil filter as with an air filter- it gets more efficient as it loads up. In fact, that true of just about any type of filter you would use in an automotive application; cabin filters, fuel filters, etc. FLOW decreases as efficiency increases but both oil and air filters have (or are supposed to) enough area to maintain sufficinet flow over a calculated "real world worst case" FCI.


Jim Allen
Keepin' the Good Old Days of Four Wheeling Alive
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