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air filter vs fuel economy - controlled test results

air filter vs fuel economy - controlled test results

air filter vs fuel economy - controlled test results

(OP)
regarding thread71-214125: air filter vs fuel economy (tricky question?)  

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."
 

RE: air filter vs fuel economy - controlled test results

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

- Steve

RE: air filter vs fuel economy - controlled test results

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

RE: air filter vs fuel economy - controlled test results

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. :)

RE: air filter vs fuel economy - controlled test results

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

RE: air filter vs fuel economy - controlled test results

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

RE: air filter vs fuel economy - controlled test results

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

RE: air filter vs fuel economy - controlled test results

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?

RE: air filter vs fuel economy - controlled test results

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

RE: air filter vs fuel economy - controlled test results

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.

RE: air filter vs fuel economy - controlled test results

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.  

RE: air filter vs fuel economy - controlled test results

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.

RE: air filter vs fuel economy - controlled test results

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.

RE: air filter vs fuel economy - controlled test results

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.
 

RE: air filter vs fuel economy - controlled test results

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

RE: air filter vs fuel economy - controlled test results

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.

RE: air filter vs fuel economy - controlled test results

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...

RE: air filter vs fuel economy - controlled test results

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
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: air filter vs fuel economy - controlled test results

Quote:

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.

RE: air filter vs fuel economy - controlled test results

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
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: air filter vs fuel economy - controlled test results

I guess if the car is auto, a (throttle linkage based) kick down trigger could be tripped more often if the lack of power is compensated for by more aggressive use of the throttle pedal.

- Steve

RE: air filter vs fuel economy - controlled test results

When these type of disscussions have come up in various places, I have always compaired a plugged airfilter on a newer electronically controlled engine, is like going up the highest mountain pass you could find. The controls are going to maintain the correct mixture, so a plugged airfilter should actually give you better gas milage, with of course a loss of power. Because with the loss of air, there will also be a loss of fuel supplied.  

RE: air filter vs fuel economy - controlled test results

thx for the link ,very interesting

RE: air filter vs fuel economy - controlled test results

I've just returned to this thread.

Thanks Pat, your suggestion is noted, but rejected.

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