air filter effect on mpg

It affects every car, the perfect air/fuel ratio is about 15 to one, as it is most if not all cars do not get this perfect ratio unless turbocharged , even then the ratio may not be 15:1. So anything that limits the air supply affects performance and MPG.

 

It would have to be absolutely filthy to effect the part throttle MPG of a modern spark ignition vehicle with a throttle plate.
When the resistance in the filter goes up(dirty) your foot(or the ECM on drive by wire) corrects for it by opening the throttle plate more so the total intake resistance is the same(you get the same volume of air to meet the load).
So it shouldn't much matter at part throttle.I don't think the spark motor in the Prius runs at full throttle at low RPMs-lugging- if it did, like a diesel with no throttle plate-then it would effect FE
Charlie

 

Doesn't the Prius get air thru the throat assy? If air is impeded at slight pedal position then it must also be impeded at any other pedal position. OR: is air coming into engine from somewhere else? Under your baseless theory you never have to change your engine filter. I hope you are not cheating and changing your filter???

 

there was a study done by EPA on effects of dirty filter: http://www.fueleconomy.gov/feg/pdfs/Air_Filter_Effects_02_26_2009.pdf

in a nutshell it reduces power but effect MPG is negligible.

 

Free air flow through a modern closed loop fuel injection system is not nearly as important as in a carbureted vehicle. Every so often I or someone I know will find a giant rodent nest inside the air cleaner. Surely this has impeded air flow but there was no meaningful difference in mpg before or after. These are not baseless claims, see that study that Oak Ridge National Lab did. One of the vehicles tested was a 2003 Camry 4 cyl, which had less than 1% difference in fuel economy. Acceleration effects were more significant but still hard to notice.

 

An interesting study, but it states under conclusions Para 4.1 that the same degree of restriction could not be obtained on the 2007 Buick Lucerne as compared to the older pontiac. And to have attempted this degree of restriction would have exceeded design parameters. Also performance was affected. The whole test was inconclusive with premature conclusions being drawn. Not real life at all. However if anybody is seriously interested in improving fuel economy....just stuff a couple of rats down the air throat! :cheer2:

 

No, not really. It should not really matter how dirty the filter gets, it even seems possible from the Oak ridge study that at some point in time after you have about 30000 miles on the air filter that your mileage will IMPROVE, because of a small layer of dust that has accumulated! So either dashing some loose fine dirt on the filter or finding a couple of rats, maybe...3 rats would be better. If in doubt call up the Oak Ridge Lab, they should have a toll free # :cheer2:

 

just put on good LRR tires.. huge difference

 

Won't matter in a modern EFI vehicle-and it is the same reason that CAI systems won't improve PART THROTTLE FE.
I read many many posts in a GM truck forum about various CAIs or K&N filters improving FE 2-3 mpg-15-20%.
The posters aren't lying and they are absolutely convinced the gadgets are improving FE on EFI trucks.
Old days- carbs- yes dirty filters were poison-not now.