Air Filters Replaced Too Frequently.

[UNC017]

Originally Posted By: George7941

Atmospheric pressure is around 360in wc, so a 5in restriction is around 1.4% restriction. On a carbureted engine the mixture will richen a small amount from that restriction, but with fuel injected engines monitoring manifold pressure and mass air flow, I don't think this 1.4% restriction would have any effect at all on fuel in a fuel injected engine.


The only effect is slightly reduced power at WOT/max RPM. Its just as though you couldn't open the throttle the last 1.4%, so you're giving roughly 5.6 horsepower on a 400 horsepower engine (assuming that horsepower is directly propotrional to airflow). Not very much, really, and at anything less than WOT/max RPM you're not losing anything because you can just crack the throttle a little wider to compensate for the slight filter restriction.

 

[daves66nova]

I have about 30 of these Filterminders. Some are almost brand new.

 

[onion]

I liked George's idea here, and installed a restriction gauge on my nasty old '94 Corsica last time I had the air cleaner off... found it among the junk in the shop. The one I used was designed for turbocharged diesel engines, and goes up to around 20" H2O (or thereabouts)... which I think is higher than you'd want on a naturally aspirated automotive engine. But it also has graduated marks at 8", 12", and 16".

We occasionally get medium-duty GMC trucks in the shop with a V8 engine that runs on LP gas. Seeings how this is a naturally aspirated, spark-ignition engine, I'm assuming that the maximum air filter restriction that this engine can tolerate would be fairly similar to my own vehicle- definitely more similar than a turbo-diesel. The filter restriction gauge on these trucks goes into the 'red' at 10" H2O. So I'll probably change my filter when it gets up to 8" H2O, or thereabouts.

 

[George7941]

Originally Posted By: marvinlee
Great question: "Exactly how much [air filter] restriction is "too" much?" There is no easy, or even correct, answer. Some factors include: 1) The engine's duty cycle. An engine running at constant RPM and near-full throttle cannot tolerate as much filter restriction as a consumer engine that very seldom operates at full power. An example of the former would be a commercial irrigation pump engine. Most cars would come closer to second example. The operator's preference is another factor. Some of us don't mind losing a percent or so of power at peak throttle, while many would. Much depends on whether one has a giant V8 engine with surplus power, or an underpowered car that needs every bit of its meager horsepower. My view is that car makers should design cars that monitor air filter restriction and integrated it with the vehicle's typical usage experience. Something of the sort is often done with oil change monitors and the air filter offers fewer engineering challenges. Millions of dollars are wasted every year in replacing fully functional filters. It is green to conserve.



Agreed. I am surprized GM hasn't come out with a AFLM, similar to their OLM.Could be a good selling point. There is already a Map sensor.Given Baro and WOT vacuum readings and knowing the restriction offered by a particular engine's intake ducting, it is fairly simple to calculate filter resriction.

The quickie oil change places will not like it though, since they make their money on upselling items like air and fuel filters.

 

[Zedhed]

Originally Posted By: George7941

I installed a filter restriction gauge when I bought my Sierra truck, and, at 25k mi on the air filter element, the gauge still indicates no restriction. I will probably go 50k mi before I replace the air filter element . I trust the gauge and, if it says 'no restriction' then I see no need to replace the filter element. I tested the restriction gauge by applying 5in water column vacuum to it and the gauge registered 5in wc.

On MD trucks at work, I only replace the air filter elements when the restriction gauges indicate restriction and the trucks go 100k to 150k mi before needing a new filter element.

The gauge I used on the Sierra is Fram SP3539.

You will save money by avoiding needless filter replacements if you intall a restriction gauge. Also, everytime you remove the filter element, there is a risk of dirt falling in. The service manuals for the MD truck engines advise against opening the air filter box unless indicated so by the gauge.

I live in a big city. If I lived in the Canadian countryside I could probably go 75k mi on air filters because of cleaner air away from a big city.


Is that Dexcool sludge in your overflow bottle? Better get that checked out.... just kidding

 

[Virtuoso]

[censored].. for $40 I can get darn near 4 filters for the Malibu or Windstar.. That's about 120,000 miles worth of filters if I change them liberaly. But it would be great for giggles!

 

[Samilcar]

Yeah, for $40 it wouldn't be worth it to me. But you can pick up slightly used ones on Ebay for $15-$20.

 

[Bill in Utah]

You can get the filter minders at Napa for $20-$25.

Look here

Bill

 

[mitsuman47]

Or, Amazon for $16 + shipping (unless you have more than 25 bucks worth of junk to buy. then shipping is free!).

http://www.amazon.com/Wix-24801-Air-Filt...7279&sr=8-1

 

[GMBoy]

Originally Posted By: mrsilv04
Originally Posted By: Bill in Utah

My 2000 Silverado (and Moms 2002) has them standard. My 2004 GMC does not.

That's odd Bill... My 2004 Silverado has one.

I have the factory towing package (which I believe includes a HD air cleaner)... could that be why I have one?



Yes - tow package trucks get the air filter life monitor and the airbox is larger. My 2006 has it. Never paid much attention to it.

 

[Bill in Utah]

Originally Posted By: GMBoy
Originally Posted By: mrsilv04
Originally Posted By: Bill in Utah

My 2000 Silverado (and Moms 2002) has them standard. My 2004 GMC does not.

That's odd Bill... My 2004 Silverado has one.

I have the factory towing package (which I believe includes a HD air cleaner)... could that be why I have one?



Yes - tow package trucks get the air filter life monitor and the airbox is larger. My 2006 has it. Never paid much attention to it.


Well that would answer it. Both my 2000 and Mom's 2002 has towing packages.

My 2004 does not. But it does have a minder now!

 

[Bill in Utah]

Originally Posted By: mitsuman47
Or, Amazon for $16 + shipping (unless you have more than 25 bucks worth of junk to buy. then shipping is free!).

http://www.amazon.com/Wix-24801-Air-Filt...7279&sr=8-1


Even better!

 

[George7941]

Originally Posted By: Zedhed

Is that Dexcool sludge in your overflow bottle? Better get that checked out.... just kidding


It is definitely Dexcool that you see there, keeping the cooling system pristine and sparkling clean inside.
I was planning on filling up with fresh Dexcool last year but did not get around to it. I am planning on doing it this year.

 

[Shaman]

Originally Posted By: daves66nova
I have about 30 of these Filterminders. Some are almost brand new.


Off to the for sale section?