Fram air filter for TJ-poor mpg

LOL!

Aha!

Something has ben bugging me about the new Jeep's crappy mileage....

Some folks say they can get 17 to 20+ mpg which is getting a bit close to what the old 258 carb engine gives me and what my Cherokee 4.0 gives,

23+ mpg and others say they only get 13 - 14 mpg....

Could it just be the air filters? I don't use foam covered filters.

I think that would sure be worth looking into!

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Jerry Bransford wrote:

What is the best air filter for the 4.0 Wrangler?

Joe Carroll

2K-TJ

There are some simple truths...And the dogs know what they are." Joseph Duemer

Nearly anything paper and nearly anything but K&N. AC-Delco's paper element air filters are very good.

Jerry

Joe Carroll wrote:

What's wrong with K & N? I used one on a Stealth Twin Turbo for 3 years and seemed to get better mileage with it, so put one in my TJ too and haven't had problems. Does your recommendation apply to both the tube add-on and the regular box air filters? Thanks in advance.

Matt

On the other hand, when I changed the iar filter in my (new to me) `96 Cherokee I found that the previous owner either seldom changed it or liked to leave it running outside a laundromat's vent. The element was completely gray and caked in dust. Changing it out for a new Fram made not one bit of diffrence in my gas mileage, though.

-- "I defer to your plainly more vivid memories of topless women with whips....r" R. H. Draney recalls AFU in the Good Old Days.

Simpleanswer --- a CLEAN one, and in light of the previous posts one without a foam wrap. The LARGER (surface area) the filter the better the engine efficiency and filter efficiency - reason: particulate in air needs 'residence time' inside the filter media to become trapped; the LARGER the surface the area the lower the velocity of air through the filtration media and the higher chance that the particulate gets trapped ON the surface of the filter instead of INSIDE the media. Once debris starts to build up INSIDE the media, the service life and efficiency (P) quickly degrades. Think BIG, much bigger than what DC provided !!!!!!!!!

Oil bath filters are ..... worthless unless you run exactly at the precise rpm (volumetric flowrate of intake) specified for the filter. The BEST removal with an oil bath is approx. 80% of particles and if you dont run at the exact flow rate the removal efficiency degrades drastically (both @ higher and lower rpm / flowrate CFM).

Obviously the foam wrap was detremental (in this case of the previous discussion/posting) as it obviously increased the operating pressure differential across the entire filter set - probably due to slopply glueing and a semi-open-pore choice of foam. In most air filtration applications the foam is detremental to pressure drop. The higher the pressure drop the richer the resultant mixture. I take my hat off to the poster who knew his engine intimately enough to know that something was wrong (foam overlay) and simply removed it.

BTW - auto air filters (dry paper pleated types) vary all over the map with respect to removal efficiency and differential operating pressure .... even from the same 'manufacturer' and from lot to lot .... even so, you usually get what you pay for. Just remember BIGGER is vastly better.

(I'm deeply involved in filtration engineering and would NEVER not have an air filter in place.)

Matt, My stock air filter (2001 TJ) had foam glued onto it also. Replacements, OEM, didn't. Never could find out why it was dropped from OEM filters - don't know if it added more filtration or robbed gas mileage. I can get 19 MPG only on flat highways, 5th gear, no headwind. I do run 35" tires so that's good. 17 MPG is normal for me.

Andy

loosely

Matt, I use CarQuest filters (which are WIX) and haven't had any problems. Sometimes those air boxes are tricky to seal back together and will cause loss of MPG for some reason. It happen to me not too long ago. You might check the duck work coming to the air box for junk. I know around here squirrels will deposit nuts for the winter most anyplace in an engine compartment. Tom T

And it still runs?

Bless America, =DFill O|||||||Omailto: snipped-for-privacy@aol.com

I didn't start charting my mileage until after I got a clone K&N. But I know if I drive smart I've gotten upwards of 20mpg...best was 22mpg....but I'm usually 17 just keeping up with the F1 drivers on the 400!

If I run 120-130 kph on the 400's I get about the same drop. If I kick back at 105-110 or so I get better, the 23 mpg or 11L/100 km. On Hwy. 7 running less than 100 kph, closer to the speed limit of 80 I get up to

26 mpg.

I have a 200 mile gas station to gas station trip I take regularly so have lots of chance to check it. Almost $5.00 more to run it with the front hubs locked in because of snow potential on that 200 miles.

I run a generic filter air I believe. Chain store brand. My carb stays pretty clean for all the dirt I run so they work well. Been using them since the 70's on all my vehicles.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

SteveBrady wrote:

A K&N is ok for a street vehicle but it filters too poorly for a Jeep that is offroaded in dusty conditions. Tests show it really lets the fine dust through, not a good thing. I have to run a K&N because my OBA compressor takes up the space where my OE air filter box used to be but get it so it was filtering well enough for my desert wheeling, I ended up placing two pre-filters over the top of my K&N. Yes the combination can still provide more air than my 4.0L engine is capable of consuming. :)

Jerry

snipped-for-privacy@nospamyahoo.com wrote:

I'm the same as Mike with the xj, if I stay in the 'normal" range of 110-115 I get great mileage, less then 100 (if I want to be like the dumb stupid #$%^&*&*& who insist on driving the 400's during a snow fall, when they can't drive for shit to begin with" then I get pretty close 26mpg. Yeah the few times I decide to take the jeep into the warp speeds the posers and rice burners do I get right down to 15-16 mpg. This of course is all relative to how many transport trucks I decide to draft. :) In 2 weeks I'm going North with the truck, I figure I'll get about 20 mpg depending on 3 things, 1 how many ricers I see, 2 how many transports I follow and 3 how much of the trip the wife is awake for :)

Snow...

You know, one thing I've been curious about is how the tire size will relate to mpg - taller tires give you higher or lower mpg. I can argue it either way in my head.

Ken

Ken Knapp did pass the time by typing:

I went from 215 to 225 and saw doodle difference. Generally I think that city mileage would get worse with taller tires (more power required to accelerate) and highway would be better (lower rpm for a given distance)

I've seen a greater difference in milage from dirty air filters, fuel filters, spark plugs, burned rotors, and vac leaks, than anything.

I drive 135 miles a day to work and back. When I first got my Jeep I it had 30x9.50's on it. Mileage? Almost exactly 20 mpg. I went with 235-75R15 replacement tires and my mileage never changed a bit. Still takes 7 gallons a day to commute.

-- Old Crow '82 Shovelhead FLTC 92" 'Pearl' '95 Jeep Wrangler YJ TOMKAT, BS#133, SENS, MAMBM, DOF#51, SPUNGER#2

Isn't there a leverage problem involved, too? You're asking the device to move a slightly heavier weight at the end of a longer lever (the radius from hub to ground).