More XJ Mods
 

This is not a success story yet, but I thought to post on what I'm working on.

Extensive modifications are being made to make the Jeep off road ready. Stiffeners have been added to the unibody and the stock rockers have been replaced by 2x6 3/16 tube steel sliders. Probably added about 200 lbs to the vehicle, but the underside is smoother and the body is more rigid.

The fender flares have been removed and the inside of the front wheel wells have been smoothed out.

The cooling system gets an upgrade too with a higher temp thermostat, electric fan conversion, and new radiator and transmission oil cooler.

The electric fan conversion will probably net the most gain, but it is impossible to tell with so many changes done at once.

Ditching the mechanical fan decreased my fuel consumption from 0.64 gph to 0.59 gph at idle. A significant improvement! Highway mpg seems to have improved too but I need to drive more before I can make a judgment on that.

Nice to see a fellow XJer in here. Yours is looking good, and i can't believe the economy your getting for what it is.
Mine is a 95 4.0 with the AW4. 33's, 4.56 and 5" lift. I am currently running at 12.5 mpg, which is 18.8lt/100km where i am from (Australia). I have taken it over a weighbridge, and she has half a ton of extras on her. Winch, roof rack, bull bar, rear tire carrier, etc..

I did have the triple fan setup from Dirtbound offroad. Had two set up to come on early, and last one to come on at higher temps. Also have a Derale tranny cooler. My whole cooling system is new. Also have hood vents, ceramic headers etc.
I could not stop the Jeep from running hot on the beach. So i went to the ZJ viscous clutch fan. Amazing. Jeep never gets over half way on the temp gauge. Usually runs at 88C which is 190F.
With my fuel use so high, and running an OBD1 XJ, i got a great MPGuino color touch from a fellow forum member. Its set up in my Jeep and very accurate. So now i can start making mods, and seeing exactly what effect they have.
My XJ has the power/comfort setting on the transmission. I found this to have a big effect around town. In power, the torque converter doesn't lock up until 70kph which is above the speed limit. In comfort, it locks up around 45kph which is below the speed limit around town. With the lockup, i am getting much better economy, as the engine isnt revving so much.
I have ordered a Hayden XJ clutch fan, as i think it will improve economy over the ZJ fan, but still provide me the cooling i need. I found my triple fans were constantly on anyway, which puts more load on the alternator.
Right now, i find my driving style has improved using the gauge for economy. Faster acceleration to get up to higher gears, slower top speed etc...have all helped me increase economy by about 2mpg.
Hope we can share some ideas..
Cheers,

https://tqrr7g.bn.files.1drv.com/y4m...&cropmode=none

https://rvoakq.bn.files.1drv.com/y4m...&cropmode=none

https://tvplha.bn.files.1drv.com/y4m...&cropmode=none

Very nice looking XJ! If overheating is an issue, I would definitely recommend the electric fan setup I got. I found an aluminum 3 core radiator with electric fans to go with it for only 250 usd. It works almost too good. It was pretty cool this morning, so I didn't even have to turn the fans on. I'm sure I will mainly use the fans when I'm off roading.I have found that removing the mechanical fan allows me to get up to speed slightly faster and my engine revs up faster too. I will be installing a higher temp thermostat, which should help me get better fuel economy.

Looks like you have a pretty cool tent on your roof for overlanding. If you're willing, I would suggest removing the roof rack and keep a tent inside. I removed the stock roof rack from my XJ for a small gain. You would probably see quite a nice gain from taking yours off.

I have quite a few mods planned when I have the funds. I have found a company that makes rear spoilers for our jeeps. I would also love a banks header for both power and economy.

Rear spoiler may be good Taylor95..

The roof rack will be staying on, as i use it to carry everything, and on the side is an awning for when we are at the beach. Looking at getting a roof top tent as well. There are going to be lots of things that i know wreck economy, but i won't change.
Staying below 65mph, converting the fan, spoiler, keeping a good tune, etc.. are some of the ways that i am hoping will help to bring economy down a little bit.
I have an aluminum radiator, high flow pump, 195 stat, all new cooling system.
I also had the 3 fan electric setup. Even with all 3 fans going flat out, it could not pull enough air to keep the Jeep cool on the beach. Where i live, the temps are regularly 35-40C (105F). With the Jeep at high revs on the beach, the temps would scream up, even with all 3 fans going max. What is the 3 fan system that you have purchased? I was maybe looking at the Taurus fan mod for the future. I will go from the ZJ to the XJ clutch fan and see how much that affects consumption at hot idle.
I might also air my big tires up to 40 psi. I will be looking at swapping out my O2 sensor soon, as i noticed it is not quickly switching between lean/rich.
Ive only just got the MPGuino working well, so want to do small things at a time to find what works.
Be interesting to see what works on yours as well!!

Below is a pic of the fans i ripped out. They just couldnt cool her down enough. This was only 2 months ago. I never changed anything else except swap out to the ZJ fan, and the motor NEVER goes over half way, even in 100F temps.

https://6pnmng.bn.files.1drv.com/y4m...&cropmode=none

Old vs new headers...

https://002avq.bn.files.1drv.com/y4m...&cropmode=none

Keeping things cool on 100f days on the beach is still a major consideration...

https://nwtl7a.bn.files.1drv.com/y4m...&cropmode=none

This is the electric fan setup I got:

https://www.amazon.com/gp/aw/d/B079DM3NR8#

I think I should say that my Jeep really does not run hot compared to what I've heard about others. It rarely goes over 210, even when off roading in hot weather. This setup though seems extremely effective compared to what I had. When it is cool out my coolant temp is around 188, with all the fans off. Can't say it will work for you, but I'm happy with it.

What headers are those? Do you have a link?

In addition to all that, I have 4 hole injectors, a custom CAI, catback exhaust, and a 62.5 mm bored throttle body. All those seemed to help efficiency except the injectors and the CAI.

That radiator and triple fan setup looks pretty good. The front of your Jeep is alot more open than mine. I have a light bar and winch in front. It kind of blocks off air supply. The triple fans worked good most of the time, but when it got really hot, and the engine was really working, they couldn't keep up in my application. I guess everyones Jeep has its own unique characteristics.

On a side note, i did fit Grand Cherokee rear disc brakes to my XJ. Still retained the ABS. I find them great. Low maintenance and no rolling resistance.

The headers i got from here in Australia. I had them ceramic coated in a chrome type color. https://bestmufflers.com/bshop/index...roller=product

Ive also got 4 hole injectors. Australian 777 injectors. Also E3 plugs. The engine runs very smooth, idles great and never misses a beat. I had to replace the cam sensor a few months ago. She just died with no warning. I keep spares of all the sensors. Mainly NTK brand.

One of the best and cheapest mods i did was the TV cable. Bleepin Jeep does a small YouTube vid on correct adjustment. It was amazing. 5 minutes, and completely free and it completely changed how my Jeep engine/transmission felt and shifted.

I had a CAI, but now have a snorkel setup. I might wrap the airbox in insulation. I was going to get a K&N filter, but the more i read, the less i want one.

I was going to go up an octane rating in fuel at the bowser, but i was also told the 4.0 runs best at the lower ratings, and not worth the difference in cost.

I have a free flow cat, and a throttle body spacer, but not the larger throttle body.

Whats your thoughts on resetting the computer after doing a mod. I know the Jeep supposedly runs of a preset bunch of tables and learns all the time.
I wouldn't mind resetting mine and having a baseline. Not sure if the Jeep responds instantly to each mod/upgrade.

Keep up the good work..

Cheers,

What have i done?
Replaced O2 sensor.
Replaced MAP sensor.
Replaced Temp sensor.
Replaced ZJ clutch fan with XJ clutch fan.
Tire pressure to 40psi.
New fuel filter.
Lightened my foot.

Currently about 1tl/100 better economy. (.6mpg).
I have reset adaptive memory, so computer is still learning.
Hopefully in the next few days she will know what i have done and start responding.

Cheers,

.6 mpg is pretty good! That is about a 5% gain for you.

I've never really noticed a difference from resetting the computer but I'm sure it makes a difference.

Funny enough, the largest gain I have noticed is from my larger throttle body. In theory it doesn't really make sense, but that was the first time I ever hit 19 mpg in my jeep. I'm pretty sure a spacer will be a waste of money though.

Right now my jeep isn't even driveable. The fans killed my battery. I will be upgrading to 136 amp alternator so my jeep can handle the load from the fans. I think my stock one is only rated for 90 amps.

Thanks, i guess 5% is better than nothing.
I will be doing a lot more evaluation this week doing longer runs.
I have a throttle body spacer. Doesn't really do anything. I might look into the bored body.
I have the 136A alternator. Got it from Summit. Had to do some research, as my 95 RHD had a weird self tensioning system that would not accept the bigger alternator. Solution for me was the 96 RHD mounts. It bolted straight in then.

The fan was a good mod. I could feel more power and hear less noise. My temps have gone up from 88C to 91C avg. Thats a good thing, as i have noticed my hot idle mpg is improved above 88C. I am currently at 0.47 gallon per hour on hot idle.

Ive just been looking at rear spoilers. The US ones are dear. There is an English mob that makes a cheap one. Are they worth doing?

This is for the pre-update.. https://www.ebay.com.au/itm/JEEP-CHE...W/181310296727

Cheers,

Wow your idle fuel consumption is really low! Is that US gallons? I wonder if getting the new intake manifold style and new headers would help me in that area.

I think the spoiler is definitely worth it. I'm not sure how much it would help in your situation though, because you keep a few things on your roof. I imagine it would yield at least 1-2 highway mpg on a jeep like mine. That's one thing I'm still hoping to get.

Yep, thats US gallons. Works out to 1.8lt/hour @ hot idle (88c. 190f).
There is a big difference if it is in gear at the lights. It goes to about 2.3lt/hour, and then if your in gear at the lights and have the aircon on, well, it burns 2.7lt/hour. That 50% increase in fuel consumption idling at the lights in gear with the aircon running.

That is impressive. As I stated earlier, my Jeep consumes 0.6 gph at hot idle. This was after removing my mechanical fan. Can you attribute any of your mods to your low idle fuel usage? I have done a lot of the same stuff as you but my Jeep uses like 30% more fuel than yours at idle.

When I put my obd1 mt2500 scanner on, my fuel trim is at -5%. My injectors are at 4ms. I do have 777 injectors. My rpms are just over 700. The engine had to be up near 180-190f to get the good hot idle readings. My mpguino is calibrated spot on. Resetting computer makes readings worse. Adaptive learning makes it get better. ANY slight vacuum leak makes it worse. I have a tranny cooler that kept kicking in early, as I have the trigger for that hooked up to my old triple fan setup. The load on the alternator was making fuel use at idle worse, so I disconnected it. Also, my aux fan was coming on early. I changed the sensor, and now it doesn’t come on til 210f I think. Anyway, removing All load from the alternator helped a lot. The aircon is a massive one that sucks juice at hot idle. All my pulley bearings are new, and my alternator is new. My engine is tuned to perfection, all new sensors, plugs, coil, cap, leads. No cracks in header, as it’s new. I run an oil additive called Xado. Very expensive, but I had a noisy lifter and it fixed it and made the engine run quieter.

Cheers,

Well, the unofficial results are in. I did over 100k's of mixed driving today and the Jeep is running so smooth and the economy has definitely improved.

Just to recap, i fitted a touch screen MPG gauge to my OBD1 XJ 4.0. Wired through the injectors and speedo. After calibration it is very accurate and can give me instant and avg lt/100, distance to empty etc..

After getting base readings of avg combined 18.2 lt/100 and an 80kph (50mph) reading of 14.5lt/100 a few weeks ago, it was time to do some work on the Jeep to improve things.

This included swapping out the ZJ clutch fan to a Hayden XJ clutch fan. New O2 and MAP sensors. Pump tyres up to 40 PSI. New fuel filter. G70 friction modifier in diffs and Nulon E10 in engine. Reset computer.

After driving today, the computer is adapting well and bringing the economy back into check. At 80kph i now average around 12.5lt/100. This is a US 18.82MPG. Combined at the moment is averaging around 15.9lt/100 which is a US 14.79MPG.

Considering my XJ has a lot of mods and weighs a lot more, i think the figures are starting to become reasonable. A brand new unmodified 1998 XJ 4.0 Auto had an official government EPA rating of a combined 16MPG and 19MPG highway rating. https://www.fueleconomy.gov/feg/noframes/14742.shtml

I'm not far off those figures now. A steady foot helps alot. Also, my transmission has the power/economy button. Economy locks the torque converter up at 45/50 kph (power setting is about 70kph), so that driving around town, i notice it uses a lot less fuel.

Cheers,

Those are pretty big gains! What are those things you are putting in your engine and diffs? Currently I use 10w-30 full synthetic and 70w-90 synthetic gear oil.

My Jeep is a lot more efficient now that I replaced the battery and alternator. I drive mostly highway (~65 mpg or about 105 kmh) and I average 22 mpg. I'm very happy with this but I think I can do better. Most of my sensors are original, so I think replacing them might slightly improve my numbers.

Taylor95, 22mpg is very good. Your getting 3mpg better economy than what was reported for a new one.

The additives i put in the XJ diffs and transfer case contain PTFE friction modifiers. I use it to reduce friction and make things run smoother.

My engine has done 201,000 miles (325,000 kilometers). It was starting to sound a little mechanical with very mild lifter noise. The additive has just quietened it down and made it run smoother. Sounds more like a sewing machine now.

I'll definitely need to look into those.

Have you looked into any engine mods? I definitely want to get a set of roller rockers (greatly reduced friction), a mild cam and maybe rebuild the whole thing with increased compression.


On forums I've heard people say that the roller rockers would give you an easy 1 mpg. They are expensive though.

That claim sounds highly suspicious. Motorcycles and a lot of high performance cars use bucket lifters. A roller rocker's pad still slides on the valve stem, and the roller is a plain bearing, so the friction is on the same order of magnitude (as opposed to e.g. roller bearing vs hydrodynamic journal bearing, where you have a 10x decrease).

Higher compression ratio definitely helps a lot since you're only at 8.8 if I'm reading specs on the internet correctly. If you want to mess with cams, going higher duration while keeping overlap the same will reduce torque but increase part load efficiency.