3/4 grille block results with '95 Grand Cherokee

[texanidiot25]

Ah, the real challenge-- Making this 318 V8 (5.2L) average at least something different. For such a small V8, it sure gets miserable fuel economy, on average 13-14 mpg. Currently a project to flip and sell, but more and more loving it's comfort and off-road abilities (yes, I do. Made good use of the skid plate today in fact), I decided to start messing with a grille block. 6 of the 8 openings for the Jeep were closed, lower grille still open. Stayed cool in all traffic in today's lovely 75 degree weather, just a hair warmer.



The results? On the flattest piece of highway I can find in Austin, +4-5 mpg at 65 mph on average (23-24 mpg), and +2-3 at 75 mph (20 mpg). And interestingly enough, 2 mpg while climbing the hills. This thing is dead on consistent to average 12 mpg at 65 or so mph running uphill on the way home. Grille block in place, 14 mpg.

Biggest problem is that it's full time 4wd, it's always powering the front axle. And you can't pull the front driveshaft with out ruining the center diff in the transfercase.

[vacationtime247]

Best mpg average with my '97 Jeep Grand Cherokee limited was 20. That was on the interstate with the cruise at 70. 14 mpg isn't terrible in one if it's mixed city / highway. Does your's have the CV joint type front axles or the U-joint? It's got the Quadra Trac 4WD unit too right?
Wife asked me just today if I missed the Jeep. Said for long trips with the kids, yea. But I'd never get one to use as a daily driver. It's a gas hog that demands to be fed $20's
VT247

[texanidiot25]

Depends how much traffic, but 13-14 is what I get if I have to stick around in downtown traffic, with highway driving. 12-13 in pure city traffic. And there's nothing that can be done about city fuel economy, I drive it as best I can but it's a beast to get it back up to speed, with the whole drivetrain to spin. Highway fuel economy can be improved, and by this test, as much as 20% which is solid.

I love it as a highway cruiser, so much more comfortable than the CST10, CRX, and Miata were at the speeds I use between here and Houston. And it's pretty good in city, very tight turning radius and it's fairly small to me. I love it, but it costs about 70 bucks every 2 and a half weeks, which isn't that bad (I dd'd my CST10 for 2 years, 3.73 gears with no OD!), but I do miss the CRX and Miata, which barely took over 20 bucks to fill, and both of which could average at 75-80 mph what this one averages at 50...

Yes Quadratrac (Viscous center diff), and the CVT style joints up front.

[bluejoey]

Nice results with the JGC! But why did you sell the CRX HF?

[texanidiot25]

Originally Posted by bluejoey

Nice results with the JGC! But why did you sell the CRX HF?

Depressingly low horse power, after I moved to Austin, I realized it couldn't take some of the hills here that I hit daily at posted speeds. And it had over 270,000 miles. I'd love a 2nd gen CRX HF, little more power and EFI. Also, I'm tired of cars with no A/C!

I put it up on craigslist for trade, and threw a 1500 dollar price for S-n-G's, and someone wanted it for that. I only had 650 bucks in it. Bought a Miata, loved it to death (Some of the greatest driving roads in TX are here in Austin) but that particular one was a bit of a lemon, and I didn't want to sink the future dollars into it. Sold it for 2500, started building the CST10's new 4spd OD trans with the profits, and was offered this GC for 1000 bucks, *****in' deal and when I goto resell it I can double my money quite easily if I can sell it for at least 3000. It's a great truck, and I love it offroad.

For a college student, it's been a healthy way to make money.

[KITT222]

Jeez, I wish I could make money that fast. I brushed up on the saga of your CRX and MAN-iata on XMS the other day. So many cars in such a short time.

That's one big improvement on the Jeep. Something so small with such good payback. Although if you're offroading, does it overheat?

[texanidiot25]

I wouldn't use these offroad, it runs warm normally.. Doing work with no air speed at the grille.

And yeah, vehicle #6!

[comptiger5000]

As far as running temps for those, make sure your fan clutch is good. If it is, as long as it's not over 220*, you're not overheating. It's only if it passes that point where it's a concern. For reference, 1 tick mark right of center on the temp gauge is about 223*. 210* is normal running temp.

Yeah, the mpg sucks, but they're not city cruisers. Get it out on the highway, and it's much better. As far as the transfer case, if you get binding in tight turns, look into swapping it. When the viscous coupler fails, that can hurt mpg slightly.

However, if the unit is working properly, it really doesn't make an mpg difference. The later version of the quadra-trac unit that came with my Jeep works a bit differently, so it's safe to pull the front shaft, but it's still full time 4wd normally. I pulled the front shaft at one point, and later swapped to a Selec-Trac case (front shaft installed), and didn't notice any mpg difference at all, city or highway.

Also, for best VC lifespan and mpg, when setting tire pressures, measure distance from rim lip to ground to get it even front to rear for even rolling diameter to minimize drag in the transfer case. This will likely have a couple more psi in the front tires than the rear.

I might have to try the grill block on mine for the long highway run home next Friday. I don't think I need all that cooling in February. Of course, around town, I know I'd get mine pretty hot with a grill block.

[texanidiot25]

After snow drifting in the morning in Austin, and mudding/trails with it that night in Houston, I think I killed the VC, it's started to chirp at full lock turns. Could be alignment, could be VC, I haven't really taken a look. Fuel economy is no different from when I bought it.

It's a pig in the city, but it's still pretty maneuverable for a truck it's size. Love it on the highway though, it's nice to have a quiet highway cruiser.

Normally it runs on the 2nd line to the left of 210, and with the grille block on and with A/C it was just under the line just to the left of 210. Off road, it'll sit at that same point, or sometimes right at 210.

As far as the grille block, I kept the center open for the fan clutch, hoping that it wouldn't come on, but in doing so the oil cooler is blocked. It's on the passenger side of the grille, and I think that's where the extra heat would be from. I think your 5.9 has an electric fan, if so I'd keep the oil cooler unblocked with the 2 open slabs.

I'm still surprised the 5.9 has cooling problems, needing a beefier cooling system, hood vents, etc. It's not like it's that much more powerful, and certainly for other vehicles that share same motors with different displacements, they don't have to go through the drastic changes to keep their larger versions cool.

[comptiger5000]

The 5.9 doesn't have cooling issues, per se, but it doesn't have a lot of extra cooling capacity. Keep in mind, it has an e-fan, rather than the mech fan. The ZJ was already a warm running vehicle under heavy load (such as towing), so the bigger engine was enough to push it a bit farther. The hood vents don't flow a heck of a lot anyway.

As far as your running temp, it sounds like it's running way too cold (2nd mark left of 210* is 155*). I'd say it's time for a new 195* t-stat. It should run between the mark left of 210* and the 210* mark itself pretty much all the time.

I'd move your grill block to keep the tranny cooler unblocked personally. These trannies don't like heat at all. Mine actually didn't have the factory tranny cooler (not included on 98s), so I added one.