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Old 02-02-2012, 02:15 AM   #1 (permalink)
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Turtle About to get myself a Jeep. MOD ADVICE NEEDED!

I am about to get myself a 1999 Jeep Cherokee. I do realize that this hog is for sure not made for Hypermiling, However i decided to accept this challenge. My long term goal is to double the EPA.
Im kind of young and never had someone to teach me so i don't know much about cars, however i do hope to learn.

To start off this thread i have a few questions. honestly im full of these and i hope you guys are willing to help me out and stick around through the whole transformation, as i plan to post lots of detailed pics, and possibly video updates as time goes on. Wish me luck guys.

1. Grill block...is this safe on a jeep? and how effective is this?(keep in mind im from ohio, however i do LOTS of traveling to VA and much farther south every month with business.)

2. Wheels...Bigger the better? or am i mistaken?

3. Lowering...Will lowering a jeep give me a noticeable increase in MPG?

4. Any tips as far as simple and or complex aero mods i could look into to improve my future MPG?


Thanks so much guys. Really looking forward to hearing any feedback from anyone with experience. It would be really cool to hear any success or failure stories from other jeep owners.

Like i said before, i hope you guys are willing to help me out here and stick around through the whole transformation, as i plan to post lots of detailed pics, and possibly video updates as time goes on. Wish me luck guys.
Hopefully next time you see me, ill be a proud owner of a gas guzzling BRICK and ready to start the process of beating the jeep EPA.

-Brandon

P.S. HERE SHE IS...



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Old 02-02-2012, 05:38 AM   #2 (permalink)
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Good luck with it!! You'll get support here, for sure.

Does it have a manual transmission?? Being a committed hypermiler, I wouldn't buy any other type. Except maybe paddle shifters, but only if the guts is one of those newer computer controlled dual clutch things with no torque converter.

Can you drive it in 2WD mode? Full time 4WD will hurt your mpg. That's one main reason Subaru hasn't gotten their cars up into the higher mpgs like most Japanese cars of similar size/weight.

Grill block -
Get a ScanGauge, I think about $150. One of the available displays is a digital readout of engine coolant temp (labeled FWT for "water temp"). With that info you'll know if your grill block is OK. I keep that showing always. I need to vary the amount of grill block when the seasons change. It reads out in (approx) 2 degree increments so it's much better than the "cold", "medium", and "too late, you wrecked your head" indications on a regular needle gauge.

Wheels and tires -
If you don't need off road or snow/ice capability, highway tread will give you a definite improvement. I keep 2 sets of tires mounted on 2 sets of wheels because I need snow tires for winter. When you spring for the $$ for that, get LRR tires - low rolling resistance. My LRR Michelin snows roll nearly as smoothly as my summer tires.

Higher overall rim + tire weight hurts you in city driving due to the energy costs of acceleration/deceleration. The rotating weight doesn't hurt you so much on the highway; once you get that wheel + tire spinning it tends to stay spinning.

Narrower tread is better than wider (sorry, doesn't look better but it rolls better). Taller overall diameter will give you an advantage at highway speeds, if they will fit in your wheel wells. Less rpms for the same road speed. But your speedometer won't know you have taller tires so you have to make the corrections by doing math. There are tire size calculators to help with that.

Lowering -
I'm not sure. If nobody answers here, go to the "Aerodynamics" subforum. Probably already answered there. But see my next section on mods; the belly pan is easier to work on if the car isn't low to the ground like my Civic.

Aero Mods - should help at any speed above 30 mph or so.

If you don't need it, sell the roof rack back to the dealer or just take it off.

Belly pan is something I'd suggest. Cleans up the air flow underneath, and is stealthy. My brother has a Wrangler Unlimited (4-door) and it looks like you could easily get underneath and mount thin Lauan plywood on some angle brackets to cover the whole underbelly. Prime the Lauan first and it will be fine. Or use Coroplast (google it; buy it at sign shops) with some aluminum bar stock stiffeners added using pop rivets.
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Old 02-02-2012, 07:16 AM   #3 (permalink)
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If I bought that jeep, the last thing I would do is lower it. It kind of defeats the whole purpose of having a jeep.

Could I ask why you are buying such a vehicle? I assume you won't be taking it off road as lowering is an option.

The jeep is a great vehicle....if you intend to use it for it's designed purpose. If your needs are an on road 4x4 wagon, the subaru makes way more sense.

If greater towing capability is a need, the jeep does make sense.

I suspect that at least a partial grill block would be fine. This vehicle was made for the rigors of off roading which means it should have more cooling capacity than needed for regular driving.
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Old 02-02-2012, 07:47 AM   #4 (permalink)
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Best advise you'll find is don't buy it, especially if you're going to be doing a lot of driving. I realize you want it, and its "cool", but everyone I know has issues ($$$) with them and like you said they're massive gas hogs. The amount of work you'll need to do to get it to anywhere near reasonable mileage (not even good mileage) is 4X the work someone with a normal car would have to do, and you still won't be close to anyone with a midsize car. If you search the garage you can see the majority of ecomodders who own Jeeps aren't even getting 20 mpg, and these are people who drive and mod for better efficiency.
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Old 02-02-2012, 08:25 AM   #5 (permalink)
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i have a 99 jeep cherokee sport, jacked up 3", runing 31/10.5/15, roofrack, ect,ect. thay are a gas lover's and i would not change a thing to it for better gas. im always off road and haveing fun in the snow with it. my people cant believe some of the thing i do in it,and yes i've put it on its side on the back roads and had to get my nabbers trackter to pull my over to all 4 tires again. my self i've just got a car (1988 honda civic dx) that can be made into a hypermiler is ez'er.
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Old 02-02-2012, 09:40 AM   #6 (permalink)
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Ecomodding a jeep is like making a submarine float better.. Driven a similar jeep on vacation and it is a great car, but by ecomodding you would most likely just loose most of its offroad capabilities. Your time and money would be better spent buying a second car, one that is small and economical to start with, and just drive that around. A small toyota or VW type of car will get better FE, unmodded, than you would ever be able to pull out of that jeep.
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Old 02-02-2012, 10:10 PM   #7 (permalink)
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All those "don't buy the Jeep" comments are probably your best advice.
I did my best to answer your original questions but I think no matter what you do to it and how you drive it, the Jeep will be a gas hog. Gosh I hope it has a manual trans; nobody wants to pay to replace an automatic when it goes bad.

You didn't say why you want a Jeep. I've driven in all kinds of rotten winter weather, with 4 snow tires on a RWD or FWD car. RWD gets some cement blocks in the back for better traction, in addition to the snow tires.

Maybe in your business you absolutely have to have a macho car? My brother is in construction management. I'm sure he'd be an instant wuss with that crowd, if he showed up driving anything not big, boxy, and made in USA. If ya gotta have a truck for image, get a 4-cyl Ford Ranger. They are the most fuel economical pickups, at least for the years I checked on the EPA site. Pay attention to features + details because some get better mpg than others.

If you plan to go off roading, well that's nice recreation. Are you in a position to have a vehicle for recreation and also a true fuel sipper for those trips to VA?

Sorry - I'm not trying to be mean. Trying to put some ideas in front of you. Maybe some of this is stuff you hadn't already thought of.

I commute 55 miles each way so that's about 550 mi/week. I did the math, and in 3 years driving the Civic, the gas savings compared to the car I drove before was enough to pay for the Civic! If you truly cover some distance, the $$ for gas really adds up - or adds up much more slowly, depending on what you drive.
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Old 02-02-2012, 11:15 PM   #8 (permalink)
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Yep, if it's for image get a 2WD 4cyl manual Ranger and make an aero topper. You'll be able to get into the 30's MPG wise. With a Jeep... good luck. $4000 truck... um. Buy a $500 economy car with a manual and drive that for a year while saving back up for the Jeep.

I drove my '65 F100 for two months last winter averaging 15mpg, even highway. It was painful. The Probe, though, will get 40+mpg tanks all day long. And it's rated for 24mpg combined. Get something economical and smart first, then buy the toys.

Of course this is assuming you don't need the Jeep for, say, carrying four people and towing something. Otherwise a Ranger will be so much better.

Edit: EPA combined is 17 or 18 mpg. That means with some pretty involved hypermiling you could see mid 20's. And I mean, pulse and glide all the time on the freeway.
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Old 02-03-2012, 05:23 AM   #9 (permalink)
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When I owned my Cherokee, I was getting 19-20 mpg highway pretty consistently doing 70-75 during the summer. Gas mileage was often down to 14-15 mpg during the winter. I didn't have any mods besides a cheap custom intake (It was a foot or so of exhaust pipe with a large cone filter on the end, attached to the stock rubber neck on the throttle body). I removed my roof rack, and had slightly larger than stock tires that were old and hard enough they probably contributed to my higher mileage.

The 4L Cherokees are damn fine vehicles from a mechanical reliability standpoint, but I wouldn't expect any great efficiency without some major mods. They're not remotely aerodynamic, so there's room for gains there. Ditching the mechanical fan for an electric wouldn't be a bad idea.
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Old 02-03-2012, 05:29 AM   #10 (permalink)
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Quote:
Originally Posted by Extrudedcow View Post
... They're not remotely aerodynamic, so there's room for gains there. Ditching the mechanical fan for an electric wouldn't be a bad idea.
E-fan conversion is definitely a good thing to do.

As far as the aero - the Cherokee basically has a box shape with a big square back end. You can smooth up the unevenness of the sides (maybe), add rear wheel skirts and a belly pan, but IMHO the only cure for the big back end is an aero boat tail like the aerocivic. Not what I'd call a beginner's project, on a vehicle of this size.

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