(Much of this post comes from a
similar post on the RV.net forums.)
Hi all,
We just returned from our second camping trip, a three day weekend venture up to Hills Creek State Park in PA. We had the Inmotion tune performed on our Jeep Liberty CRD which adds a claimed 35hp and 45ft-lb. I can't vouch for the exact gains, but the tune accomplished its goal of helping give a little more oomph up the hills. For steep grades where I had to fall back to 3rd (locked) before and was still still slowly losing speed, I could now pull them in 4th (locked) and maintain speed or even accelerate slightly. When locked in 3rd with the tune, I was able to pull every grade on this trip.
One grade was fairly mild but several miles long. I took the grade in 4th gear (locked up) at 55mph, which is 1750rpm. After the first mile, the temperature gauge started to climb. By the end of the grade, the needle was one tick below 3/4. This seems hot, but my fellow Jeep forum members have scan gauges which read the actual coolant temperature from the computer and they found that 3/4 on the gauge is still a reasonable operating temperature. I'll try to get an idea of exactly what temperature this needle position indicates.
Running hotter is an expected side effect of the Inmotion tune. In the front end, the layering is:
- A/C condenser (top half), transmission cooler (bottom half)
- intercooler
- radiator
Basically, the radiator is on the losing end of the deal. With the higher boost pressures, the intercooler and engine both generate more heat, and the engine runs hotter under heavy sustained loads. The solution is to replace the restrictive factory muffler with a high-flow aftermarket muffler. The factory exhaust system is shared betweeh tne 2.4L 4-cyl gasser, the 3.7L 6-cyl gasser, and the 2.8L 4-cyl diesel. It's just not up to handling the flow of the boosted 2.8L. With the exhaust opened up, the exhaust gas temperatures are significantly reduced and the engine operates cooler (and makes a bit more power as a bonus).
I have a Magnaflow cat-back exhaust system on order. It's stainless steel and mandrel-bent 2.5" pipe, and will be a nice complement to the Inmotion tune. Reports indicate that it sounds identical to stock at cruise, and the turbocharger whine is just a hair louder when you stomp the go pedal. I'm a fan of quiet exhaust systems, so this is a nice upgrade for me. The stainless steel will also be a welcome upgrade for the Northeast daily driver salt duty that this vehicle will get.
I am also looking into adding an additional transmission cooler before the factory cooler in the nose. I am friends with the owner of a local transmission shop, and he does excellent work at great prices. He loves the CRD, and after getting a taste of what it can do with the Suncoast install, is eager to further upgrade it.
Once we got near the state park, the roads were unpaved. At a stop sign going up a steep hill, the rear wheels threw a lot of stones at the trailer and I struggled to get traction. I put the transfer case into 4WD part-time which locks the center diff, and was able to pull the trailer right up the hill from a stop. I could have used 4WD full-time (works on paved roads too) but the transfer case operates with an open differential in that mode, and I figured that it was less stress on the transfer case to keep it locked when pulling a heavy load up a loose stone road.
Once we got to the park and got to our site, the short wheelbase of the Jeep again paid off in spades. Our site was level, but the road going by it was a steep, narrow uphill. I was able to throw the trailer into a tight bend backing up (wasn't too far off from 90 degrees), then swing the nose around and "catch back up" to straighten out. It really made my trailer backing-up skills look better than they really are. I would have been hours of entertainment for my fellow RVers in a pickup truck.
I got a little ahead of myself unhitching, and didn't follow the correct sequence of steps to unhitch the Hensley. I managed to catch the safety breakaway cable and pull it off, and I also forgot to take the tension off the weight distribution bars before pulling the Hensley stinger out of the hitch head. I can now appreciate the value of having handy checklists. I don't care to do that again. I'll need to replace my breakaway brake cable before our next trip.
On the trip there, we went 271.2 miles on 16.9 gallons of diesel. That's 16mpg, but part of that tank (about 90 miles) was unhitched, and part of that was in 4WD full-time exploring back roads near the Grand Canyon of Pennsylvania. On the trip back, we traveled 180.2 miles on 11.4 gallons. That's 15.8mpg, and only about 10 miles of that tank was unhitched. I'm pretty happy with those numbers. For the second half of the trip back, we put the windows up and turned on the A/C. That may have actually helped our mileage. I kept an eye on the temperature with the air conditioning on, but it did just fine. It was about 85F outside.
I stopped at a CAT scale on the way back to weigh in our traveling configuration. First I pulled the Jeep on the scale and unhitched the TT. The weights were:
STEER AXLE 2400 lb
DRIVE AXLE 2080 lb
TRAILER AXLE 5020 lb
GROSS WEIGHT 9500 lb
These weights were without my wife and I in the Jeep but with both dogs loaded. I realized this too late once I stood on my tiptoes to reach the call button. As you can see, most of the weight in this little beast is over the steering axle even without the front seat occupants. It was also nice to see that even with my wife and I added in, we were still under the GCVW rating of the CRD (just a smidge over 10k, will grab the manual later and edit).
To measure these weights, I had to unhitch the Hensley on the scale. While I was hitching up, a trucker came over to me and said, "Hey fella, just so you know, you're holding up a hundred thousand dollars of load, okay?" Even with hitching up straight back, it took me a few tries under pressure to line it up right. Doh, that was fun.
Once hitched up, I set the weight distribution where I normally kept it, drove back around on the scale, and reweighed (only $1!):
STEER AXLE 2460 lb (+60)
DRIVE AXLE 2640 lb (+560)
TRAILER AXLE 4400 lb (-640)
GROSS WEIGHT 9500 lb (+20)
I originally set my weight bars by ride feel and by eye, but I was hesitant with the unibody to err on the aggressive side without being able to actually measure the weight distribution. As you can see, I was way too timid with the weight bars! The transferred tongue weight isn't too far over the 500lb U.S. rating. I turned each weight bar adjustment nut four full turns, drove around the scale again, and reweighed (another buck!):
STEER AXLE 2520 lb (+120)
DRIVE AXLE 2580 lb (+500)
TRAILER AXLE 4400 lb (-640)
GROSS WEIGHT 9500 lb (+20)
Better, but still nowhere near enough. I pulled off the scale and found I was able to only get three more turns on the adjustment nut before I hit the stop. It looks like I'll need to bring the coarse adjustment pin up one hole to get some more adjustment range, but I wasn't too keen on doing this without talking to Hensley first. I asked the scale operator when the scales weren't busy, and he said between 10pm and 6am when most drivers are sleeping. I'll repeat the experiment another time and get it set up better. Even with the modest additional amount of weight transferred to the front, my wife and I both agreed the ride and stability was noticeably better. With the proper distribution, I think it will feel a lot better than it does now. The new Pirelli Scorpion ATR load range D tires should also help improve ride stability. It's good timing too, as the current Firestone Destination A/Ts don't have a whole lot of tread left.
While we were unhitched at the campsite, I recalled what Andy Thomson (on RV.net) mentioned about play in the receiver. I put the Hensley stinger in the Jeep receiver, and sure enough there was some side-to-side play of the 2" stinger bar in the receiver opening! It's maybe 3/16" of movement at the far end of the stinger bar, but it's still a source of play. A very slight bit of extra width on the stinger bar would lessen this play. Is there an easy way to accomplish this? I was thinking of something along the lines of a coat of epoxy paint on both sides, or maybe a strip of some sort of very thin plastic adhered to both sides. I read a post on the RV.net forums about welding a bead along the side of the 2" bar and grinding it down to add a bit of width and reduce hitch play (not Hensley specific), but this seems a little more labor intensive than a couple coats of epoxy paint. Any ideas?
- Chris
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