Aerodynamics question

[redneck999]

Is there a site or info on the actual aero of a cherokee? For those of us that spend a lot of driving on the interstate, is it the flat grill? Not enough slope to the windshield? A bigger air dam in front? Just one of those things i wonder about.

[prerunner1982]

A little of everything... high stance, vertical grille, not so sloped windshield. But sorry, I don't have any #'s on the drag coefficient.

[4.3LXJ]

No numbers here either. And we all mess those up badly

[redneck999]

I wonder if there is a site that you can simulate wind drag, you know with smoke that you can adjust?

[prerunner1982]

I don't know, that would be pretty cool. Be able to see how certain mods would effect the wind flow/drag. Lifts, racks, lights, winches, etc.....

[redneck999]

I've been googling like crazy and it appears that i have to be rich to get a good program.

[Carves]

I've been googling like crazy and it appears that i have to be rich to get a good program.


Which is why most forum posts about the subject ... are hopeful guesses .. :D:D


What are you trying to do ...
Make a Prius out of the XJ ...
Improve the factory setup where possible ...
Make up for lifts, tyres and stuff, changes, after mods ...
Or just get rid of that damned annoying whistle, from the side mirrors area .. :D:D

Some numbers here --> http://ecomodder.com/wiki/index.php/Vehicle_Coefficient_of_Drag_List

FWIW ... apart from removing the roofrack, fitting a set of flush hubcaps and sideskirts ... You probably wont improve much/gain benefit over how the XJ left the factory.

... but you might have some fun experimenting .. ;);)

[OrangeXJ]

The xj is a brick I don't think there is much you can do to change that

[redneck999]

Brick or not haven't you ever been curious about something? Not reinventing the wheel here just looking for answers!

[07Negative]

Yes to being rich to get your hands on the software. Shape and size of the solid does matter. So does speed, but thats easy to get (duh). If you like physics, here's the formula
FD = 1/2Pvsq. CDA (sq is squared). It's easy math but boring information.

[XJ Wheeler]

I can understand where you're coming from. I don't get why people say "its a jeep, if you good fuel mileage get a car", etc. Yes, they're bricks and are old school inline 6s but saving more is a universal thing, as well as efficiency. The less fuel the vehicles uses also has other "pros". If its using less fuel its also easier for the vehicle to move, and thus less strain on everything. Say you gain 2mpg, it may not be much but it anything helps and you still get to drive a mighty XJ. :D

Sent via messenger pigeon - i talk, he types.

[redneck999]

I don't go offroad except at the farm and such, I and my families always bought 4wd because where we live we are not high on the priority list of the first roads plowed. Many times you have to look for the tall weeds at edge of the road and hope to not hit the ditch at the edge. When i gotta have my cookie fix i don't want anything standing in my way! Since mine is on the road most of the time if i could do anything to improve anything i would, Mine is already compromised by being lifted and taller tires but that doesn't mean it can't be improved upon. If it was proven that 3 coats of wax and yellow streamers on your shocks gained 2 mpg i'd do it, but of course i would have to butch it up to compensate with chrome skull valve stem caps!

[4.3LXJ]

If your use is primarily highway and snow, I have found that the Michelin LT tire is a great snow tire. Best I have ever driven on. They come in sizes up to 32" tall and are engineered for milage. Not having lugs on a tire will increase milage

[redneck999]

Right now i'm running cooper discover atr tires.Yeah it's gotta go through snow, pull a trailer haul a wheel chair and make me look good! I have been contemplating going to the Badlands over in Attica Ind. I heard the have old people trails over there, safe for us geezers. I did all my hard wheeling when i was young, flipped a cj-5 end over end and rolled twice, landed on my wheels to boot!

[Mudderoy]

The xj is a brick I don't think there is much you can do to change that

Invisible force field in the shape of a saucer, or sphere. :D

Oh! Just remember to turn it off occasionally other wise you'll suffocate! Ask me how I know...

[redneck999]

If i built said force field, how much space would be required? Parts availability? Tin foil hats and underwear?

[Mudderoy]

If i built said force field, how much space would be required? Parts availability? Tin foil hats and underwear?

I wouldn't do it. There is still an issue if you intersect with another force field and some minor time travel and hair loss. Personally I don't like the hair loss.

[redneck999]

You didn't say anything about hair loss when you just casually tossed the idea out there. Reckless science, this is how the whole coke and mentos thing started. Thanks to free thinking individuals we may soon carded for potentially dangerous sweets.

[Mudderoy]

You didn't say anything about hair loss when you just casually tossed the idea out there. Reckless science, this is how the whole coke and mentos thing started. Thanks to free thinking individuals we may soon carded for potentially dangerous sweets.

Hey that's weird, "Dangerous Sweets" is what I had on my 70's custom van!

[redneck999]

That's what my wife calls me. Are you stalking me or trying to mirror my life, i worked very hard for that nickname. Wait, are you my long lost twin that i didn't know i had and somehow our lives have paralleled and have now crossed? This science stuff is tricky, i now understand the phrase "don't cross the streams" I'm messing with forces of nature that are truly out of my control, why didn't i heed your warning?

[Brasscatz]

We've got to do this to a Jeep.....
http://dsc.discovery.com/tv-shows/mythbusters/videos/dimpled-car-minimyth.htm

[redneck999]

Myth busters is the enemy of cherokees everywhere

[Brasscatz]

Myth busters is the enemy of cherokees everywhere

Yeah, I've seen them destroy several... not cool. lol

[redneck999]

It's incredible the amout of times i have seen cherokees in tv shows and movies. I wonder if its some kind of record?

[denverd1]

aerodynamics and cherokees. never thought I'd use those words in the same sentence

[redneck999]

Think about it.... is it the 4.0 engine or the vehicle? If you put a smaller engine in it,(2.5?) it will get better mileage. so i wonder if the 4.0 efficiency can be improved or if that's all you can get out of it? Hell i had a 4 door nova with a 6 cyl that i inherited and it got 24-25 mpg.

[redneck999]

Whats the mileage of a Grand with a 4.0? Aside from having angled white plastic headlights, is there much difference in the angle of the windshield and more plastic, whats the difference? Fueleconomy.gov says a 98 grand with 4.0 auto says 14 city and 19 highway.

[Mudderoy]

Whats the mileage of a Grand with a 4.0? Aside from having angled white plastic headlights, is there much difference in the angle of the windshield and more plastic, whats the difference? Fueleconomy.gov says a 98 grand with 4.0 auto says 14 city and 19 highway.

Isn't it heavier?

[drakan1908]

The Grand is heavier. Not sure how much. I have found that with a smaller motor you are always driving with your foot to the floor. I had a s10 pickup with a 2.8 v6 that got worse mileage than my ZJ because I was always driving with my foot planted. A guy at work says his V8 gets 15 around town and about 22 on the highway. My ZJ gets about 10 around town I don't know about highway.

Sent from my XT907 using Tapatalk 2

[4.3LXJ]

There are two factors brought up. One is the box style. The other engine size. In my carburated 2.8, I consistently got 22mpg with a 3" lift and 31s and crappy CA gas. A bit underpowered, yes. Now, with a 4.3L V6 I consistently get 16 mph around town and 18 mpg on the highway on an 8" lift. But, I drive like an old lady around town and this transmission I have has a much deeper overdrive than the 14% overdrive in Jeeps. Also as stated, the 4.0 is an old school engine with fuel injection added on and is not an efficient engine by todays standards. And neither is mine by todays standards. Things on my wish list are a new cam and 99/00 heads with heart shaped combustion chambers. I think it is possible to hit 20mpg highway with it.

[gary63]

A lot of thing has to be considered weight, shape, engine size hp tork displacement and gears. All more weight more power to move it but if your engine put out more hp and tork at a lower rpm and the displacement is not real big you will use less gas . Diffrent gears big tires over small tires steel rims over aluminum. Lead foot over smooth take off and stops.