Air filter question
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Elder User
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Air filter question
Gentlemen,
Everywhere I read, article after article, it is said that a dirty air filter reduces fuel mileage. I can not understand this and think it is an urban legend. The maf sensor and others make any corrections necessary and the only consequence should be decreased power. I believe mileage should actually increase because less air is available under heavy throttle conditions. Isn't it just like driving at a higher altitude?
I am not recommending dirty air filters but the theoretical question is interesting.
What do you guys think?
Ken
Everywhere I read, article after article, it is said that a dirty air filter reduces fuel mileage. I can not understand this and think it is an urban legend. The maf sensor and others make any corrections necessary and the only consequence should be decreased power. I believe mileage should actually increase because less air is available under heavy throttle conditions. Isn't it just like driving at a higher altitude?
I am not recommending dirty air filters but the theoretical question is interesting.
What do you guys think?
Ken
Senior User
Joined: Oct 2003
Posts: 124
Likes: 0
From: Northern California
I'm no rocket science, but less power = more gas used to accomplish speed, towing, hill climbing etc?
I think your right on the computer adjusting everything (hence my hesitation to buy a K&N or knocking the screen out of the MAF, Cold Air Induction etc.)
Good thought though, I always wondered what engineers think when the dream something new up and what would happen when the tweak certain things. As they say, for every action there is a opposite reaction.
Aaron
I think your right on the computer adjusting everything (hence my hesitation to buy a K&N or knocking the screen out of the MAF, Cold Air Induction etc.)
Good thought though, I always wondered what engineers think when the dream something new up and what would happen when the tweak certain things. As they say, for every action there is a opposite reaction.
Aaron
Post Fiend
Joined: Apr 2005
Posts: 5,720
Likes: 5
From: Washington state
another point to ponder is that flow particle testing has proven that a used air or oil filter is more effective at filtering out smaller particles...theory is that trapped particles decrease openings between filter fibers
dirt and particle injestion thru poor filter media selection and leaks in after filter air feed are now the largest cause of engine wear and early failure
gotta love that Goofy Lube bang the yuppy woman's air filter on white paper towel routine....just remember, they salt & pepper the paper towel before hand, better than owning a gold mine....$25 air filters
the air box, filter and air feed in these small engine Aeros is purposely designed far over engine needs capacity that some air flow restriction will never even be noticed....
even better fool's gold mine....owning K&N filter company
marketed to yuppy men with weak minds
dirt and particle injestion thru poor filter media selection and leaks in after filter air feed are now the largest cause of engine wear and early failure
gotta love that Goofy Lube bang the yuppy woman's air filter on white paper towel routine....just remember, they salt & pepper the paper towel before hand, better than owning a gold mine....$25 air filters
the air box, filter and air feed in these small engine Aeros is purposely designed far over engine needs capacity that some air flow restriction will never even be noticed....
even better fool's gold mine....owning K&N filter company
marketed to yuppy men with weak minds
Last edited by 96_4wdr; Nov 23, 2006 at 10:33 AM.
Freshman User
Joined: May 2006
Posts: 43
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From: Riverside CA.
I think the answer may have to do with the engine running within its designed operating parameters. The engineers optimize fuel efficiency for given operating conditions, when the engine falls outside those limits (perhaps due to a dirty filter), the computer compensates but the optimizations have shifted.
Originally Posted by ken1mod
Gentlemen,
Everywhere I read, article after article, it is said that a dirty air filter reduces fuel mileage. I can not understand this and think it is an urban legend. The maf sensor and others make any corrections necessary and the only consequence should be decreased power. I believe mileage should actually increase because less air is available under heavy throttle conditions. Isn't it just like driving at a higher altitude?
I am not recommending dirty air filters but the theoretical question is interesting.
What do you guys think?
Ken
Everywhere I read, article after article, it is said that a dirty air filter reduces fuel mileage. I can not understand this and think it is an urban legend. The maf sensor and others make any corrections necessary and the only consequence should be decreased power. I believe mileage should actually increase because less air is available under heavy throttle conditions. Isn't it just like driving at a higher altitude?
I am not recommending dirty air filters but the theoretical question is interesting.
What do you guys think?
Ken
Posting Guru
Joined: Aug 2002
Posts: 1,041
Likes: 1
From: Orland USA
A dirty/plugged air filter is like turning the choke on. The more plugged it is the more gas it'll pull. To much and it will flood out.
I had a ford that would start great, then go for about an mile and stall out. Sometimes it would start back up, most of the times not. Removed the air filter to see if it was getting gas. It would start up and run. Put the Air Filter back on and turn around and hope you got it back home before it stalled out again.
Finally I said it has to be the air filter. Checked it and it looked almost new. Took it out and drove it 20 miles without a problem.
Put the air filter back in and made it about a mile and it stalled out again.
Went and got a new air filter and never had the stall problem again.
So yes a dirty filter can cause it to use more gas.
JaY
I had a ford that would start great, then go for about an mile and stall out. Sometimes it would start back up, most of the times not. Removed the air filter to see if it was getting gas. It would start up and run. Put the Air Filter back on and turn around and hope you got it back home before it stalled out again.
Finally I said it has to be the air filter. Checked it and it looked almost new. Took it out and drove it 20 miles without a problem.
Put the air filter back in and made it about a mile and it stalled out again.
Went and got a new air filter and never had the stall problem again.
So yes a dirty filter can cause it to use more gas.
JaY
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Postmaster
Joined: Jan 2003
Posts: 4,417
Likes: 3
From: Durham, NC
Originally Posted by JTHill24
A dirty/plugged air filter is like turning the choke on. The more plugged it is the more gas it'll pull. To much and it will flood out.
I had a ford that would start great, then go for about an mile and stall out. Sometimes it would start back up, most of the times not. Removed the air filter to see if it was getting gas. It would start up and run. Put the Air Filter back on and turn around and hope you got it back home before it stalled out again.
Finally I said it has to be the air filter. Checked it and it looked almost new. Took it out and drove it 20 miles without a problem.
Put the air filter back in and made it about a mile and it stalled out again.
Went and got a new air filter and never had the stall problem again.
So yes a dirty filter can cause it to use more gas.
JaY
I had a ford that would start great, then go for about an mile and stall out. Sometimes it would start back up, most of the times not. Removed the air filter to see if it was getting gas. It would start up and run. Put the Air Filter back on and turn around and hope you got it back home before it stalled out again.
Finally I said it has to be the air filter. Checked it and it looked almost new. Took it out and drove it 20 miles without a problem.
Put the air filter back in and made it about a mile and it stalled out again.
Went and got a new air filter and never had the stall problem again.
So yes a dirty filter can cause it to use more gas.
JaY
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Posting Guru
Joined: Aug 2002
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From: Orland USA
Bob:
That might be true in theory.....But in reality if the air filter is cutting the flow of Air, the computer would try and compensate by letting in more air.
Now where does it get the air?.....from through the air filter. Which is restricting the air flow.
That brings use back to the Flooding out because of too much gas flow and not enough O2 to cause a full ignition.
JaY
That might be true in theory.....But in reality if the air filter is cutting the flow of Air, the computer would try and compensate by letting in more air.
Now where does it get the air?.....from through the air filter. Which is restricting the air flow.
That brings use back to the Flooding out because of too much gas flow and not enough O2 to cause a full ignition.
JaY
Postmaster
Joined: Jan 2003
Posts: 4,417
Likes: 3
From: Durham, NC
Originally Posted by JTHill24
Bob:
That might be true in theory.....But in reality if the air filter is cutting the flow of Air, the computer would try and compensate by letting in more air.
JaY
That might be true in theory.....But in reality if the air filter is cutting the flow of Air, the computer would try and compensate by letting in more air.
JaY
amount of air, by opening the throttle plate with the accelerator. So, to compensate for the dirty air filter, you open the throttle plate a little further.
With a carb, when you open the throttle plate, you are increasing the amount of air and gas, and restricting the air going into the throat of the carb will act like a choke.
Former ******
Joined: Nov 2004
Posts: 4,901
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From: Salt Lake City, Utah
Ok, lets clear this up here as best I can. Ys it is true that the computer would reduce the amount of fuel used if it can't get enough air BUT, there is a penalty to this, e.g., you may have to use heavy throttle more often, and as heavy throttle is applied, the computer enriches the mixture. The computer is attempting to regulate the fuel flow and the best fuel mixture under cruising conditions. While accelerating, the computer tries to anticipate by adding more fuel. This is to mostly prevent leaning out under acceleration, and to err on the safe side, since detonation from leaning out could be very destructive. So this is part of where the inefficiency would come from. The other is very complicated and has to do with natural induction of the intake run when it is under vacuum. Basically, the intake builds up some momentum (this is where torque and peak power comes from), and when it is under excessive vacuum it looses this induction effect, and the engines efficiency drops. This loss of efficiency in the intake due to a plugged filter would cause a lack of efficiency in the engine.
Post Fiend
Joined: Oct 2005
Posts: 5,242
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From: Kiev, Ukraine
thefarelaneman is right! Yep ECU corrects the mixture but.... bad filter reduses perfomance and van runs in not optimal regimes... Air filter is cheap!!! what a reason to discuss this problem? Yep.... air filter of Mercedes Actros is expencive (up to $150), so we use it till the end of its short days, but what a reason to use old filter in aero.... too cheap problem.