Since there have been many arguments on crap K&N filters increasing mileage, finally, something to prove my point that a dirty filter only decreases power, not mileage on an EFI car.

http://www.fueleconomy.gov/feg/pdfs/...02_26_2009.pdf

 

but is a circle though, with reduced power it takes more fuel to get the original level of power back.

 

Nah. You have less available air so you will never get back to the original power level (WOT). AF stays the same no matter what (the beauty of FI) so you lose power but not mileage.

Even if you increase throttle a lot more to get some of the original (part throttle) power back, you're still only flowing enough air for the original part throttle power so you're using the same amount of fuel.

 

ok, got you. the only hole in it now is thats when the car is dumping fuel to keep the ratios in check, at WOT, (closed loop or open loop, forgot which one) it'll dump as much fuel as it can supply and thus it'll be wasting fuel...

 

With the plugged air filter, airflow is reduced so fuel is also reduced by a proportionate amount. The net result is a loss of power but not mileage.

I see what you're saying about WOT but it doesn't just dump all the available fuel. Most older FI cars base WOT fueling on the long term fuel trims. So if the filter has been plugged for a while, even WOT fueling will be proportionate. Newer cars like the TL stay in closed loop at WOT.

On top of that, there will be more manifold vacuum at WOT with a plugged filter so the computer sees this as a decrease in airflow and adjusts accordingly.

 

thats pretty cool actually. Looks like that experiment and your insight has proven the old myth wrong..

 

/thread???

haha. pretty interesting read on the first 5 posts

 

Would the dirty air filter then effectively increase my MPG by limiting the power? Like say if you floor it you will not use as much gas as with a clean air filter? LOL just throwing some fuel back in the fire...

 

Good article. Didn't read the entire article, but when talling about mpg, the notion has been around for years as the throttle plates are the restriction in the system, but for a diesel with no throttle plates, a dirty filter is harmful.

 

you got it.. but I'd still much rather have the power.. how many of us mod our cars to decrease power.. but hey.. if gas goes up to $4-$5 again.. I might extend my filter cleaning interval..


edit: Nice find btw.. funny.. Oakridge Nat'l Labs... from nukes to vehicle fuel economy.. is there anything they don't study?

 

If you drive like a lot of my friends do, then yes. I swear all they need is an on/off switch. They never use anything between idle and full throttle.

 

I hate cars.... my filter is loaded im thirowing a new one in this weekend, do I need to reset the ecu (that pedel trick) after so that the computer isnt used to the restricted air flow and gives me power back? Might be a stupid question..

 

I don't think the old myth is wrong, as it really wasn't a myth.
Just replaced with new technology so it just doesn't apply to modern automobiles.

 

I hate to disagree but I have a 2004 CR-V that my Daughter used for two years, when I got it back it was getting 13 mpg on the freeway.

I checked everything, found a fully disgusting air filter, replaced it & immediately got the normal 26.

 

I believe there are two sides to this. Cars that run speed density systems and cars that run mass air flow sensors. A Mass air flow car will have better control of the fuel where speed density cars such as our Hondas are programmed to dump fuel based on speed and RPM.

 

Speed density is primarily based on RPM and MAP. A restricted filter will show a drop in MAP vacuum, the same as a partially closed throttlebody resulting in no change to mpg.

 

Very true. It still holds true with carbureted cars but unfortunately it carried over to EFI cars.

 

Probably not necessary but it wouldn't hurt.

 

Did you or your daughter get 26 mpg? It's highly unlikely a new filter doubled the avg mpg.

 

The filter was completely totally constricted. It was black.

I drove the car 1800 miles, it was getting poor mileage the entire trip. My Daughter did not keep mileage logs nor check mpg.

On the last tank I did the math and got 13 mpg.

I replaced the filter & got 26, I have averaged 24-28 in the year since.

 

I'm astounded a clogged filter got 13 mpg. Not that I don't believe you, but I'm surprised you kept the car at idle at that rate.

 

but isnt this is vicious circle ???

dirty filter --> low power --> press pedal more to get to desired speed --> low mpg --> dirty filter ???

 

It's been awhile since I had a K&N filter, but I remember in the literature that they claim the filter actually gets more efficient the dirtier it gets (up to a point of course).

As the amount of dirt increases, smaller particles are held in the filter media than when new and clean.

 

No. Mileage is not related to how far you push the pedal. It's related to how much airflow is actually going into the engine. You push the pedal more with a dirty filter to allow the SAME amount of air as a clean filter. If more air is not available it does not matter how far you push the pedal you can't get worse mileage.

 

That's 100% impossible.

There's some variable you're missing here.

Even a dirty filter is not a restriction until you start getting heavy into the throttle. At part throttle there is no difference.

 

yeah so but for some part you have to push the pedal more to get the same amount of air in as less push on a clean filter !!! more push = more gas consumption = less mileage !!!

not trying to prove anything....you know more....am just trying to learn by asking questions and stating facts that i know....these facts could be right or wrong.... !!!!

 

The closed loop system adjusts to the amount of air and vacuum pressure. Pushing in the pedal as you say doesn't guarantee more air. The air flow will saturate at a less than threshold volume with a clogged filter and the feedback from the loop will control the amount of fuel so your simple deduction is incorrect. On a side note, can you please stop using exclamation points. It's almost as bad as TYPING IN ALL CAPS.

 

This.....coming from a guy that hopes:

I hope your finger breaks through the toilet paper?

Just kidding!! I mean ..........

Sorry, I'm off topic..just couldn't help myself

Just trying to lighten things up.

 

For your info, I never made that my sig.. but I'd rather keep it than get banned for being a bad sport. My only advice to you guys is to stay out of ramblings. Look at my ridiculous avatar! But hey, I asked for it. lol..

 

sorry man....thats how I AM !!! hope you dont take it personally, i just like the exclamation mark !!! :P now lets not take a dump on this thread, so the changes of ur finger going thro the toilet paper would be low !!!

LOL you did !!! Thanks....ACURAZINE FTW !!!

 

LOL, i already knew this.

 

I hear you, but waaaay too many threads turn into comparisons, flames, and personal attacks.

If that is preferable to sticking in a rare lightening comment, then we have problems.

I love your AVATAR, I just wouldn't have done pink

I'm out'a here

 

The reason that does not work is the air fuel ratio is always the same. Pushing on the gas opens the throttlebody to let more air in. The computer responds to more airflow with more fuel. If it does not see more airflow, it will not add more fuel. Or in other words, less air= less fuel regardless of where the pedal is. The goal is to always keep the AF constant. If for some reason the computer's AF calculation is thrown off, you still have the 02 sensors to keep it in check.

 

Is there a timeframe on the avi & sig?

ow.

 

I am in no way arguing, simply reporting my results.

I drove the car 1800 miles with diminishing mileage. I had no clue it had been neglected as it had. It had difficulty towards the end doing basic freeway speeds & going up hills.

When I got up the next day I checked the filter, it was very very constricted, I replaced it power was restored & the next tank of gas was back to normal.

Nothing but the filter was changed.

 

1 day for every post.

 

thanks !!! makes so much sense !!!

 

All this time I thought you had a thing for cute pink stuffed animals.... I was afraid to ask :theghey:

 

I love beer / booze, boobs, beef jerky, muscle cars, guns, talking about pussy and shitting with the door open.

The avie does throw off new members and members in 4G which is hilarious. I've had requests to remove it but it complements my sometimes crass personality.. lol.

 

LOL. Was there a specific thread that this originated from? I bet it would make for some good reading.