Air filter

[Jim Allen]

Let's get a little pedantic just for clarification, shall we?
IMHO, it's a bit of a stretch to say that a free-flow filter will have no positive effect on fuel economy without tests on a lot of different vehicles. It's probably generally true and most true in the modern era where it's easy to compute airflow needs and design a system to match. But if you want to go back to the days of oil bath filters and the first cellulose filters, well, some of those were restrictive enough to be a MPG issue. There are probably some poorly designed intake systems out there these days too but I don't know of any really bad ones. Basically, unless and until you run out of airflow capacity, the intake system is not a negative factor. Considering that hypermiling is all about low revs, even a system that's might be restrictive in a high-revving performance situation has plenty of capacity. A more useful pursuit would be velocity tuning for the most economical rpm range but that's pretty hard for the average person to do

[ATaylorRacing]

I had a 98 Neon 5 speed that I drag raced....I put just over 147,000 miles on it and te very first mod was to get rid of the entire air filter system and put a fine wire mesh screen over the throttle body opening. That mod picked up very nearly 2 mpg and the car ran from .20-.23 of a second quicker in the 1/4 mile. I had the same mod on a 3.0 Sundance for over 100,000 miles with the same results. No troubles with this method, but I would not do it in a desert or dusty enviroment. K & Ns never werebeter for me and sometimes were the same as stock. I eventually was getting 46 mpg in that Neon with EOC and 41 without it...which was the EPA rating. The car had 180 hp on motor and 305 hp with NOS in use.....for you gear heads it ran 14.8 in the 1/4 on motor and 12.17 at 117 mph was its best time with NOS. In front wheel drve cars I have 33 NHRA & IHRA drag race championships and 1 IHRA championship with a rear wheel drive vehicle.
I used that Neon to win Car & Driver magazine's 50th anniversary drag race.....they had limited it to 500 entries!

[talldudenumber5]

so what about aftermarket intakes with smooth flow to the intake

[AeroModder]

I get better fuel mileage with a Fram paper filter, but the K&N cotton filter gives a noticeable improvement in power and response.

There was a study done about the effects of dirty air filters (can't remember the source, but it was posted here somewhere), and the conclusions were on fuel injected vehicles, lower airflow=less gas used=better FE, but lowered performance. On carburated cars, the lowered airflow altered the air/fuel ration and degrated both performace and economy.

[Tofuman]

My K&N filter gave me slightly better FE. But not much.

[mwebb]

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

sorry people
this is the latest of three sets of test results that all show the same thing

clogged or restricted air filters have ZERO affect on fuel economy

quoted from the EPA TEST RESULTS Feb 26 2009
"Despite the filter restrictions, however, no significant changes in fuel economy were observed. Each vehicle was run through at least three rounds of FTP, HFET, and US06 tests with the new air filter, and the same protocol was repeated with the clogged air filter. The tests were conducted on consecutive days for each vehicle. This format was used to allow for the required soak time to perform a cold FTP each morning. The resulting fuel economy data for the vehicles are shown in Figs. 3.8, 3.9, and 3.10. Range bars in the figures show the minimum and maximum of the tests for each case, while the columns show the average. Test-to-test repeatability is within about 1.5%, and all of the variances between the new and clogged air filter cases are similarly within about 1.7%. The baseline fuel economies for the vehicles were all within 0–6% of unadjusted EPA certification database values (US Environmental Protection Agency) for similar vehicles.
The changes observed by clogging the air filter produced no significant effect on the fuel economy of the vehicles tested, when tested over these three standard cycles that represent a wide range of driving conditions. It is possible that there may be some isolated operating conditions under which the fuel economy may be more susceptible to a clogged air filter. However, such operating conditions are not likely to be consistent from vehicle to vehicle. The three driving cycles used here are representative of a wide range of driving conditions, as described in Sect. 1."

read this if you want ,
believe or not - as you choose -
see section 3.1.3 for test results and discussion on FE

[superchow]

Here's my two cents: After reading the following article I threw my K&N filter out and replaced it with a regular paper filter. That tiny bit in performance that is to be had isn't worth the extra junk flying into the engine possibly shortening the life of the engine.

Browser Warning

[ShadeTreeMech]

Just look at a K & N filter next to a paper filter. you can almost read through a K&N while a paper filter is lucky to let a lot of light through.

Dust is very small, so why would a filter with obvious gaping holes be a good thing?

[AeroModder]

The car they used had a MAF (Mass air flow) sensor and a turbo. My car has a MAP (Manifold absolute pressure) sensor and is naturally aspirated. Results vary.

[sarguy01]

Overly simplified, on most fuel injected engines, if there is less air flowing in, there is less gas going in. Sticking with overly simplified thinking, gas mileage should stay the same with a clean or dirty filter. So, more fuel is used with a clean filter, but less pedal is used to keep going a certain speed. A dirty filter will cause you to use less fuel, but more pedal to stay at a certain speed. Again, overly simplified but I can see why there would/should be no difference in fuel consumption with a clean or dirty filter.

K&N vs. paper. This has been debated on all different auto forums and nobody has ever proven to me beyond a doubt there is one filter that dominates all others. It all comes down to personal preference. I kept my K&N's clean and had oil samples of my truck tested and it showed that the K&N filtered just as well as a paper. Some people may have different results.