Jeep Wrangler help
 

Hello,

This is my first post here on ecomodder. I have a 1998 Jeep Wrangler with a 4.0L I6, AX-15 transmission, NP231J tranfer case, and MANY aerodynamically damaging modifications that the typical four wheeling enthusiast would install. My goal is to get the best mileage possible without removing these modifications.

As of this writing the Jeep has a wobbling harmonic balancer, a vibration in the driveline, a dying catalitic converter, overly aggresive offroad tires, and improper gearing. These problem I will address and record any improvement in MPG.

My questions to the ecomodder community are:

1) Is the cost of a computer programmer worth any fuel gains that I MIGHT get?

2) What kind of tires should I get? I am looking at the Falken Wildpeak A/T beacause of its claimed offroad abilities and its more circumfranacially comlete tread pattern.

3) What kind of muffler should I install? I have a brand new Magnaflow high flow catalytic converter ready to install. There are many mufflers out there that improve the sound (which I wouldn't mind) and claim to increase horsepower and torque (I could give hoot about horsepower, but I love me some torque!:D). What would these do to gas mileage? What about a glasspack?

4) How would the MPG's react to intake and air filter modifications?

5) What is this I hear about timing advancement and, if I did it, how would it affect the engines torque output?

Opinions on these five questions from several members would help me IMMENSELY! Please mention anything else that would help.

-Jesse-

This is not a joke, I understand how it could seem that way because I am throwing numerous methods for conserving fuel out the window just by owning a Jeep period. All I want to do is improve fuel economy and I know of many methods that I can do just that, but I would like some input from the hyper-mileaging world.

Thanks for reading.

-Jesse-

100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com

&

65+ Vehicle modifications for better fuel economy - EcoModder.com

Welcome. Check out the search function at the top of the forum if you want a faster answer from the past!

first off the tj's are an areodynamic disaster; if you have any lift, probably won't help matters.

1) definately not worth the 3-400 considering you'd probably get less than 1mpg from said mod.

2) is it an lt or a p tire; lt's weight more than p's

3) don't think it matters much on the 4.0

4) warm air is better for fuel economy; that said most "cold air" intakes aren't cold

5) there are two ways to accomplish timing advance one is cam which should increase torque and then the other is ignition advance which should bring up efficency

Other then that; i think alot can be done to the front of the tj's to improve mpg

1) cover the front diff + an inch or two

2) cover the front wheel wells

3) block in the tires(cover in most of the wheel well's)

4) minimize the dead zone on the hood(it's huge)

5) try to reduce the rear wake (via kammback/gas tank mods(ala gc gas tank slope)

ps. my best tank was 400km/55l or 13.75l/100km; average tank 340km/55l=16.17l/100km

The only part of the exhaust system that significantly affects torque and mileage is the very first part after the exhaust valve. So unless something is clogged up, don't bother.

I am planning a smooth sloped front skidplate that diverts the air down below the front axle for my CJ.

Also see about tucking up the transfer case and installing a "tummy tucker" skid plate. It will catch less air, and improve clearance.

I think the 4.0 has a locked computer, which means the best you could do is alter the sensor readings before it gets to it. I don't remember if the 98 4.0 is EFI or carb.

Vent the engine compartment, when I did so to my CJ it dropped the engine temps by 10F. I am also looking at building a skinned grill guard to divert air at speed around the grill inlet with the sides open to let air in at slow speeds.


What size of tires are you running, current mods etc..

The best way to save on gas would be to get a small car for commuting and save the 4x4 for off-roading/mudding/rock crawling. My brother has two wranglers, a 91 or 92 (I know it has a carb) and a 95 or 96, with EFI. He bought the newer one because he couldn't get the older one to run reliably with the carb. What he should have done was buy a car, since he commutes to work/school, and worked on his first Jeep to use for off-roading, which he only gets to do occasionally.

You could try to fabricate some coroplast air dams to deflect airflow away from high drag areas like the axle and dif. You could attach them as such to be removed quickly. If you can afford it, buy two sets of wheels and tires, one for road and one for AT. Too bad lift can't be changed as easily as tires.

I've seen a increase in both FE and HP/torque with the installation of a short ram CAI. On a carburetor, a WAI generally increases FE, on EFI, some cars WAI increases FE, some it decreases, some cars CAI increases FE, some it decreases, YMMV. But as a rule of thumb, CAI increases peak HP/torque, WAI decreases it.

Best thing to do though is slow down, it's an all terrain vehicle not a sports car.

THere is some work around here on an XJ that would be of help.

For tires get a set of high way LLR.
If you want to maintain off road abilities put snow chains on when you go off road. I know a guy that does this. He was tired of buying expensive mud tires ever year that got bad fuel milage so he got highway tires and chains. The highway tire and snow chain setup does better than the most expensive mud tire.
Also the highway tires last 3 years. It takes about 15 minutes to put the snow chains on 5 min to take them off.

I have a 2012 2 Door Wrangler and previously had a 97 TJ 4cyl with 5speed and 33in swampers.

I lost 3~4mpg when I switched my stock 32in tires for 35in tires. So, keep the tires thin and stock or smaller.

There are aluminum skid plates that cover the entire undercarriage. Folks in the JKforum have posted increase of 3~4mpg with that alone in highway driving. Those skids are good for off road and lightweight only downside is they are $2,000 or so.

Then you can make it lighter weight. Take out the back seats, put in aluminum tailgate, aluminum bumper, ect...

Unfortunately; almost all mods to improve MPG or reduce weight will cost a huge amount of money with TJ or JK Jeeps.

bigC