Jeep Cherokee Aeromods

[TheDon]

Originally Posted by FastPlastic

I just used a piece from a broken picture frame. So it is pretty thin, which makes it easy to curve around bends. If you want to be lazy you could just pick up a picture frame from Wal-mart $10. Otherwise if you have a local hobby store (Hobby Lobby around here). I've seen the same size sheet for about $6. Another reason I choose to do it this way, be it harder because you have 5-7 slots to fill. I can always pop one or two out if I start having heat problems.

cool, I found a bunch of transparency sheets so I'll play with those

[FastPlastic]

Ok I went ahead and uploaded more pics of my Jeep to my photo album. I think I'll just post one or two of the main ones here if you'd like more detail feel free to browse my album.

Side View


Messy Front Under Body.


Driver Side Under Body.


Passenger Side Under Body.


And A view From The Back.

[aerohead]

Originally Posted by FastPlastic

So for the past 5 or 6 days now it's been raining. So I haven't been able to work on the Jeep. Instead I started looking over photos I took last week to get ideas for what to do next. I've decided the next project is going to address the para shoot they call a rear bumper.

The fuel tank hangs really low on the Jeeps, So do I need to wrap around the tank some with the tray or can I just butt it up against the rear of the tank?

I'm guessing either way would be an improvement from the para shoot I have back there already. Just looking for input.

I just did a post on underside mods.You might want to check it out.'like the grille,happy modding!

[DifferentPointofView]

I believe that all you'll have to do to remove the racks is take some torx bits and unscrew them, then take off the crossmembers if you want to keep the rest on.

[FastPlastic]

Ok, I'm going to take the advice of most of you and work from the front back. With the exception of the roof rack. I'll save the rear bumper for later.

I think I'll go ahead and take off the cross bars on the roof rack. I'm planning on leaving the tracks because I don't want the roof to leak. Had problems with the last Jeep ceiling so don't want to take any chances.

The other project on the front end I think will be filling the Fog light/Tow Hook holes in the front bumper. Hopefully that will help push a little more air around the Jeep. I know it's not much, but every little bit counts right?

[Bror Jace]

Yes, FastPlastic, every little bit should help ... and since you are doing it yourself on a shoe-string, you have practically nothing to lose.

But I have to side with the others here that your roof rack is a killer. I'd remove it ... and if you have bolt holes going into the roof, take the bolts that go into them, give each a dab of RTV silicone on the threads then replace them. They shouldn't leak for 20+ years.

My uncle has a Hyundai Tucson with a long commute he complains he gets only 23mpg. I told him to at least take the cross-bars out of his rack (which is never used) and inflate the tires to 2psi lower than the sidewall maximum ... that might get him to 25mpg ... but I know he won't do it. Some people are funny like that.

[Bror Jace]

"Are the fender flares easily removable? Those babies stick out like big air scoops. The early Cherokees didn't have them."

Take the front ones off ... but use the rear flares as starting points for rear wheel well skirts.

[COMP]

waiting to hear the improvements

[Red]

The flares and the molding are bolt on, I'm 98% sure since I know some XJ owners install TJ flares to cover their tires

[zjrog]

I'd check local laws before covering headlights (even with clear) and before removing the flares. I know in Utah, if the body doesn't cover the tires, you won't pass safety. I also know some that take the flaresoff after passing safety, but that could one stopped by the troopers...

[donee]

Hi FastP...,

On your gas tank to bumper piece. Start flush with flow off the tank, then sweep it to a 30 or more degree angle at the rear edge of the bumper (not the midpoint of the bumper as shown). This will make what they can a "difuser", which will help pull air from underneath the car and fill in the wake better.

In race cars this is used for downforce, but due to the height of your Cherokee its not going to do much of that. Just help fill in the wake better.

[FastPlastic]

So after 6 strait days of rain, with a bunch of flooding around town. I finally got time to work on the Jeep Again. The last two grill blocks are in place making a total of 5. And going by the recommendation of fellow eco modders I went ahead and removed the roof rack cross bars to smooth out air flow across the roof.

Total cost of mods so far: $0.

And then there were five.


Roof rack cross bars removed.

[DifferentPointofView]

I think I'll go ahead and take off the cross bars on the roof rack. I'm planning on leaving the tracks because I don't want the roof to leak. Had problems with the last Jeep ceiling so don't want to take any chances.

As long as you put the bolts back in, it shouldn't be a leaking problem. Also, using silicone sealant, you probably won't be able to remove the torx screws after 20+ years unless you ruin your roof. Someone siliconed my valve cover onto the block and it was a B**** to remove (had to do the dreaded prying *shudders*).

Here's a link to the stuff I've done so far to my jeep. I'm gonna add more things on there like my block heater install. You can get idea's from there.

DPoV's Jeepin' build thread

[FastPlastic]

So I saw an ever so slight improvement in fuel economy this tank. Don't know if the aero mods had anything to do with it or just my driving. Went from 16.32mpg to 16.44mpg. Nothing big but every little bit helps. Probably would have been better had I not gotten stuck in traffic due to flooding around town.

[Smoove]

Regarding the roof rack rails: I removed them entirely almost a decade ago. I went to my local hardware store and bought socket set screws with the same thread, add a little teflon tape and a dab of touch up paint on the top (after installation) and it has never leaked and is completely reversible.

My goal was less wind noise with the sunroof open - check!

[nascarnation]

Originally Posted by FastPlastic

So I saw an ever so slight improvement in fuel economy this tank. Don't know if the aero mods had anything to do with it or just my driving. Went from 16.32mpg to 16.44mpg.

I'll give you top marks for honesty.
My similar 97 typically is in the 16 mpg range.
Basically stock with standard size low rr Michelin tires and syn lubes in all the mechanicals, a good tuneup, and driving "carefully".
All these guys on Jeepforum who claim they get 20+ are really difficult to believe.

I have picked up a newer model equal length intake manifold for a swap but am wondering if it is even worth the effort.

[Nerys]

22-24mpg is completely within the realm of possible for a cherokee with the inline 6 engine. Well at least is USED To be. I regularly average 22mpg for my daily commute. I measured my MPG for over 350,000 miles (I have over 452,000 miles on my cherokee it had 92,000 when I bought it in 1996) I wish I still had all those records but I never kept them I did the math and discarded until the next tank. I used mpg as the canary to tell me when something "was not right" with my truck. On many occassion pure highway driving I would get 24mpg and even hit 25.50mpg on one trip (must have had a tail wind :-) but that trip was a fluke. The gas station was 100feet from the freeway. I only had to accelerate a single time and then did not drop below 60mph for over 420 miles and that was to goto another gas station to fill up again. Wish I could do that daily :-)

Alas I said USED to be possible. It seems this ethanol is screwing my cherokee as well sadly :-( My first "real" tank in the Cherokee since the rebuild (new engine exhaust lots of new stuff) netted me 17mpg. that sucks. Even my worst driving did not get that low previously (unless I went into the mountains)

NOW I am slightly advantageous of a stock Cherokee I have 31" tires. this lets me travel FURTHER per revolution. IF you "baby" it and squeeze it gently on level terrain this will net you lower RPM at the same speed and as long as your not lugging you will GAIN mpg from this (think of it as installing higher "gear" rations in the tranny)

but when I goto the mountains and have to forcefully spin those meats up hills. Ouch 9mpg is not unheard of :-) hehe

I have a feeling I will never see 24+mpg ever again in my Cherokee with this filthy ethanol in our fuel :-(

BUT if you live in an area with gasoline WITHOUT ethanol then you CAN achieve very good mpg 20mpg being EASY if you do not have hilly country to deal with.

The vehicles combined epa rating is 16mpg with 22 possible on the highway according to the EPA.

[Smoove]

Originally Posted by nascarnation

I have picked up a newer model equal length intake manifold for a swap but am wondering if it is even worth the effort.

I did it to my 96, and it was not worth the effort. I used my g-tech to compare before and after (at 0, 100, 500 and 1000 miles) and saw zero performance gain. My mpg went up 2 hundredths, hardly worthy of mention. The intake that is currently on your engine is tuned to lower end power. Sell it to some sucker on ebay that thinks it will make their 4.0 a rocket sled.

As far as my mpg, believe what you will, if you are ever in my neck of the woods you can borrow my rig for a few days and you can decide for yourself. I have owned all three engine variants in 4 different ZJ's, 20mpg on a stock vehicle is difficult but attainable (although my 5.2 rarely saw above 16mpg - even on short bursts). My current ZJ is more modified than I care to admit and frankly, I am disappointed that I cant consistently crack 22mpg. I chalk it up to the nature of traffic here.

[Nerys]

Hmm ZJ is a very different beast from the XJ much larger and heavier.

[nascarnation]

Thanks for the info Jeepers.
Hopefully I have not derailed FastPlastics thread too far...