air filter vs fuel economy - controlled test results

[ivymike]

regarding thread71-214125

A government study has (FINALLY) shown that what they've been saying about filters and fuel economy has been wrong for 20 years, if it was ever right.

http://www.fueleconomy.gov/feg/pdfs/Air_Filter_Effects_02_26_2009.pdf

"Results show that clogging the air filter has no significant effect on the fuel economy of the newer vehicles (all fuel injected with closed-loop control and one equipped with MDS). The engine control systems were able to maintain the desired AFR regardless of intake restrictions, and therefore fuel consumption was not increased. The carbureted engine did show a decrease in fuel economy with increasing restriction. However, the level of restriction required to cause a substantial (10–15%) decrease in fuel economy (such as that cited in the literature3,4) was so severe that the vehicle was almost undrivable. Acceleration performance on all vehicles was improved with a clean air filter."

 

[SomptingGuy]

Proving the obvious to the stupid. A great way to spend your tax dollars.

- Steve

 

[rmw]

Oh what a relief. Now all the commercials on TV that hawk improving your fuel mileage by having your 'dirty' air cleaner changed will disappear.

rmw

 

[JSteve2]

I, for one, am glad to see the data. Too bad about the tax dollars business, but at least they weren't spent studying changes in the mating habits of the SouthWestern dung beetle in response to increased solar activity. I checked just to see if they updated their fuel economy recommendations, and much to my disappointment, they already had.

@rmw - dream on.

 

[ivymike]

I suppose it's another example of how when "common knowledge" is in obvious conflict with first principles, the first principles usually win.

 

[SomptingGuy]

It doesn't help when TV progs and auto rags try to explain engineering topics and get it so wrong. My TV has a wire cage around it.

- Steve

 

[ivymike]

to keep thrown beer bottles from hitting the screen, or to prevent reception of over-the-air programs?

 

[JWaterstreet]

What, is the government going to tell us those magnets that you put around the gas line to "align the molecules" don't work either?

When will it all end?

 

[SomptingGuy]

It's a Blues Brothers wire cage.

I've lost faith completely with the TV auto folk. I now only watch for the high jinks (which I really, really enjoy).

- Steve

 

[dgallup]

Wow, it took 3 authors & something like 16 consultants & reviewers to come up with a 27 page report to state the obvious. And they had the gall to propose future diesel investigative work should be done. Why don't they just ask diesel manufactures? I know I mapped out the effect of intake & exhaust restriction on BSFC in my first job 30 years ago. Maybe I should apply for a grant.

 

[JSteve2]

Pressure drop in the intake absolutely does affect diesel fuel economy. Not sure in the range of a typical dirty air filter if it would be noticeable, but certainly at 5 psi drop.

 

[JWaterstreet]

This effect is already well known and documented in the heavy truck industry for large over the road diesels. No need for the government to study something already well understood.

 

[JSteve2]

Still, I think we would all feel a LOT better if they could sink $20 million or so into studying it to be sure. Preferably in Barney Frank's district.

 

[apsix]

A voice of dissent, despite the subject obviously being outside of my field of expertise.

My '99 Mitsubishi Magna (Diamante) improved its fuel economy by about 20% after a filter change.

Filter was at least 5 years old. It was not obviously very dirty. The car was certainly not 'almost undrivable' before the change.
Fuel consumption figures were read off the On Board Computer display.

 

[ivymike]

well, maybe the laws of physics allowed an exception in your case?

 

[apsix]

I didn't claim that the filter change caused the improvement, although that was the conclusion I came to at the time
Perhaps the polishing of the on board crystals did it.

 

[JWaterstreet]

In the last thread on this topic, I posted my experience with my 2000 Toyota Landcruiser. It is stored winters. Before putting it away one winter, changed the oil and all filters. I log mileage regularly. Middle of the following summer, I was worried that the truck didn't have the power that it used to. Opened up the air filter; totally plugged with a substantial mouse nest! Luckily the mouse didn't chew through the filter to cause passage of tons of nasty junk.

During this whole episode, mileage did not change whatsoever; my logs from the period before I discovered the nest showed no change from the previous year, and no change after I changed the filter.

Only thing noticeable was a reduction in available power, mainly passing other vehicles...

 

[patprimmer]

Was it a carburetored or a FI Magna.

If it was FI, something else was at work, whether it be manner of use, or other things changed with the service or a spontaneous change in calibration of the on board computer or the crystals, either the laws of physics changed or something beyond your observation or knowledge changed.

Maybe we might drop into your specialised areas and start supporting obviously wrong in fact folk law, just to test the consistency in attitude.

Regards
Pat
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[RossABQ]

Maybe we might drop into your specialised areas and start supporting obviously wrong in fact folk law, just to test the consistency in attitude.

I don't see any need to be snippy; it is observations like his that undoubtedly drove the gov't to sponsor the test.

I also suspect there will be FTC (Federal Trade Commission) challenges to any claims made for mileage improvements in parts/service ads from now on.

 

[patprimmer]

There was recently a long and detailed thread on this where people who work in allied fields and who had a clue made considerable contribution based on science, fact and data.

This guy out of hand disputes those findings and the findings of the government funded project, then admits he doesn't really have any expertise, then makes a snide remark about polished crystals when challenged.

What part of that scenario does not invite a rebuff or a red flag. I chose a rebuff as opposed to a flag in the hope he might pull his head in and the thread would stay intact.

The inference re false advertising was broached in the previous thread, though from memory it was broached with no geographic inference.

Regards
Pat
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