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Motors Do air filters really affect gas mileage?

Discussion in 'General' started by daguuy, 13 Sep 2008.

  1. daguuy

    daguuy I hate lolcats

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    They say replacing an air filter will save me gas (which I might do since my car has over 170k miles), but to me it seems like a dirty air filter would just limit and amount of air that goes into the engine just like a throttle does. Would it really make a difference?
     
  2. BioSniper

    BioSniper Minimodder

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    I believe the theory is that if the car cant burn the fuel becuase its not got enough air it will effectivley run rich and modern ECU based engines will throw fuel into the engine in an attempt to get it to combust.
    As such you will have to run it harder and you will be essentialy not burning all your fuel resulting in reduced efficiency which in turn can equate to less miles for the amount of fuel you have to stick into the engine to get the performance out of it.

    Something like that anyway.
     
  3. DaveVader

    DaveVader Fast Action Response Team

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    That sounds about right. Basically, more air (that is cleaner and colder I believe) = better. Im no car expert though.
     
  4. Fod

    Fod what is the cheesecake?

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    They don't effect gas mileage. They may however, affect gas mileage.

    /grammarnazi
     
  5. Ramble

    Ramble Ginger Nut

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    Engines are designed to run on certain amounts of air. That means an air intake blockage or even removing a catalytic converter may make the engine run less efficiently.
    If it's blocking a significant amount of air then remove it.
     
  6. talladega

    talladega I'm Squidward

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    Yes, air filters can affect your gas mileage.

    Get a K&N air filter. Never need to replace it. They are more expensive but when they get dirty you just clean them and use them again. You cleaning them once a year would be a good thing.

    You car run better too.
     
  7. Amon

    Amon inch-perfect

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    Change the filter periodically. It's rare for your car's OEM filter to be dirtied and suffocate the engine because those filters are specified with sizeable headroom that the engine cannot outflow. Just a few weeks ago, my car suffered a particularly uncommon but severe case of a dirty filter. Using a compressed air nozzle, the amount of blown-out dirt, salt, and leaves was unlike anything anybody has seen before (the intake breathes from behind the front grille instead of the typical airbox vacuum design)

    My understanding is the the engine doesn't inject that much more fuel into the combustion chamber in the case of insufficient charge (air). Doing so would probably drown the spark plugs, so the computer reduces injector flow slightly and burns less potent to appropriately match the available charge air, reducing output. The injector rate doesn't scale back 1:1 to the amount of air (reducing fluid rates through the same diameter nozzle is too coarse to have that kind of accuracy) so you end up with some more fuel than the usual ratio.

    This has a direct influence on fuel economy because you need to press the pedal harder for the engine to do the same work and you use more fuel in the process. In my case, I didn't notice much of a difference in economy after cleaning the dirty filter, anyway. But, a more noticeable improvement will probably be had in much smaller, lighter cars than mine.
     
    Last edited: 14 Sep 2008
  8. Freedom

    Freedom Minimodder

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    [​IMG]
     
  9. dark4181

    dark4181 Ero-sennin-tebayo

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    Yes, having a good, clean air filter will have a positive effect on your vehicle's mileage. Changing your spark plugs and plug wires can too. Change your oil every 7500-10k miles. I use mobil one synthetic in my car and have never had any problems. Just maintain your car well, and it will treat you well

    For air filters, I use Wixx, but if you have a performance car, you can't go wrong with K&N
     
  10. woof82

    woof82 What's a Dremel?

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    I'm not sure if that's entirely true. The Air pressure sensor and lambda sensor should prevent the car running rich. But restricted airflow will result in a loss of power.
     
  11. profqwerty

    profqwerty What's a Dremel?

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    You'd have thought that the car designers have realised this issue arises so the car can figure out if the filter's dirty as woof says by an air pressure sensor in the intake manifold (very low pressure = clogged). Then it can beep at the driver until they get out and do something about it.
     
  12. mushky

    mushky gimme snails

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    Air filters are cheap and easy to replace.
    Please don't say you've done 170K on the same one??
     
  13. NiHiLiST

    NiHiLiST New-born car whore

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    They very rarely get clogged enough to make a difference. Also the pressure in the intake manifold varies a fair bit depending on throttle position, revs, air temperature, engine temperature etc so it would be massively complex to use that to measure how clogged or otherwise the air filter is.

    Car designers have realised that the issue arises, which is why the air filter is there in the first place. If it wouldn't ever get dirty then there would be no point in even having one. That's why they get replaced when the car is serviced.
     
  14. talladega

    talladega I'm Squidward

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    Sounds like he has. :lol::lol::lol::lol:
     
  15. NiHiLiST

    NiHiLiST New-born car whore

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    That would mean 170k with no servicing. Screw the air filter, I'd be more bothered about the oil!
     
  16. Otto69

    Otto69 What's a Dremel?

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    Do not get a K&N if you have a fuel injected engine. Aside from the fact that you really won't get much more power, and if you did, it would be because you were burning more fuel with the alleged-but-non-existant more airflow, K&Ns have to be re-oiled periodically. THere have been significant problems with oil droplets from thefilters polluting the little detector wire in the detector that you'll seee between the filter and engine. If that wire gets polluted, you have to replace the unit for hundreds of dollars.

    I used to use K&Ns, but I've given up on them. It's snake oil. Just replace your stock filters when recommended.
     
  17. NiHiLiST

    NiHiLiST New-born car whore

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    EFA ;) As for them being snake oil, it depends on the car. If you're looking for more power they'll make very little difference on their own, but if you've made other changes they will make a difference. They can make a nice change to the intake noise though.

    All that said, I'd go for a decent cotton filter over an oiled one like the K&N; all the benefits, none of the drawbacks.
     
  18. Otto69

    Otto69 What's a Dremel?

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    Heh, I didn't type MAF because I couldn't remember if there were mass air or speed density nowadays. And yes, while you might be able to clean the sensor wire, you might not as well. Or you might get degraded performance after trying to clean it.

    Me, I just use clean stock paper air filters nowadays.
     
  19. chrisb2e9

    chrisb2e9 Dont do that...

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    I was going to buy a K&N for my car but the idea of having to clean and re-oil it is a little too much for me. Plus i read in a few places that they have a slightly larger..... um... hole size? when they are new. This helps get a little more air and thus more HP that they are known for. But because they let more air in they can also let in more dust and dirt which is bad for the engine.
    Could be a total crock but I went with a filter that you just replace after so much time.
     
  20. daguuy

    daguuy I hate lolcats

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    It's probably been replaced by a previous owner (I bought it 6000 miles ago) but I wouldn't be surprised if it hasn't because there are so many other problems with it that should have also been taken care of (valve cover gasket, axle boot, coolant leak, dashboard lights, huge dents, completely worn out tires, etc...), though I've taken care of the more serious problems. Considering it's a cheap beaten up old car, I won't pour any more money than necessary into it so I'll just get a cheap one.
     
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