Ecodiesel towing test. Suspension sag, mpg, power, and cooling

Laramie Crew Cab, 2WD, 1290 capacity per door sticker. 24' enclosed trailer, ~7200lbs. Tongue weight ~800lbs. Conventional spring suspension assisted by Airlift 1000 airbags (rear).

http://i465.photobucket.com/albums/rr17/RangerGress/Ram/RamTrailer_zps9c51ce73.jpg

http://i465.photobucket.com/albums/rr17/RangerGress/Ram/Airlift1000_zps57777b30.jpg

Rear end sag.
Height from fender to wheel, inches.
Unloaded. Rear 12 5/8, Front 10 11/16
Trailer hitched up Rear 9 5/16, Front 11 9/16
Put 40psi in airbags, trailer still on Rear 11 1/2, Front 10 5/8
Took trailer off, 40psi, Rear 12 7/8, Front 10 3/4
Trailer back on, hitch "tilted" forward 2", weight distro bars on, Rear 11 5/8, Front 10 7/8
http://i465.photobucket.com/albums/rr17/RangerGress/Ram/WeightDistroHitch_zpse4387eab.jpg

I'm working on moving the hitch ball 2" closer to the reciever. This shortens the lever arm the trailer has to move the truck around. This is significant both for truck F/R weighting also for sway. Moving the ball 2" closer means moving the hitch 2" deeper into the hitch receiver. This requires drilling a 5/8" hole in the solid steel hitch for the hitch receiver pin. I spent a bunch of time on this today but all I did was learn that Harbor Freight drill bits are only fine until you come up against solid steel. I got about halfway thru before my drill bit was useless so I'll have to buy some better drill bits and work on that later in the week.

Lessons learned

-800lbs drops rear end 3+ inches and raises front almost an inch. That's a lot.

-40psi airbags changed droop significantly. Rear goes up almost 2". Front down about an inch.

-With no trailer, 40psi airbags don't change ride height much.

-Moving the hitch forward (towards truck) 2" and putting on weight distro bars pretty darn tight changed ride height by only ~1/8". Therefore weight distro bars don't effectively counter rear sag. Note tho that weight distro bars shift do more weight when the rig porpoises so they still fight that pretty well.

-Towing mpg. Went for a 25mi test tow on a flat freeway at 64mph. 14.1mpg. For perspective, my 2000 F-250 diesel would have gotten 13-13.5. My old 2006 F-150 5.4l would have gotten 7mpg.

Lessons learned. I had hoped to get an honest 15-16mpg so this was disappointing. The diesel in the F-250 is regarded as one of the finest diesel engines ever put into a pickup and clearly it's a hard standard to beat. Gas engines suck towing heavy loads. It looks like I ended up with a very comfortable truck that gets great mileage when used as a DD, but isn't much of an improvement towing my trailer.

Towing heat issues. It was 85deg ambient during the above test. Both my coolant and oil got pretty darn hot. Coolant 224deg, oil 237deg. I did not expect this because 64mph on flat terrain didn't seem to stress the engine at all. It's the coolant temp that got my attention. I think I'm going to reduce the concentration of anti-freeze from 50% to 25%, and see how I might optimize air flow for the radiator. Antifreeze has lousy heat xfer specs, so you don't want to use any more of it then you need to. In Savannah, GA it only barely hits freezing a couple times/yr so 50/50 antifreeze is way overkill.

I also want to check if the radiator is adequately shrouded,and I might get a different grill. Radiator shrouds ensure that all air that hits the grill has no choice but to go thru the radiator. The blingly Laramie grill looks it might be blocking a fair amount of air.

Misc. Engine has all sorts of power. Just wish it had all sorts of cooling. Trailer brake controller works well. Since the freeway was flat, I did not engage Tow Mode.

Changing the antifreeze level will likely make your problem worse. Pure antifreeze sucks, and so does pure water. It's when you mix the 2 that the properties change.

And 224 for coolant is the normt hese days. MY jeeps run @ 215 all day long with nothing in tow. And since the coolant cools the oil, the engine oil won't be less than the coolant temp, unless you have a separate oil cooler.

If you have the air louvers that open & close to control air flow thru the radiator, they may have been partially closed to keep the coolant temp in that temp range for better operation.

We disagree about the anti-freeze. A 25% solution will cool better than a 50% solution. Pure water actually works quite well, better if a wetting agent, like WaterWetter is added tho. It does not take much wetting agent to do the job. Wetting agents reduce surface tension.

It does have an oil cooler. Has to, it's a turbo. Oil temp wasn't a big deal tho. Oil will happily run at higher temps then coolant normally would.

We disagree about the louvers too. No way the louvers would have been trying to keep the coolant that hot. Sure, 224deg coolant isn't a crisis, but it's a little above the normal range also.

What I might do is just dump the whole coolant load and put in water and a bottle of WaterWetter. Then next Dec put in a little bit of antifreeze so I don't have to worry about a sudden cold spell.

RangerGress said:

-Moving the hitch forward (towards truck) 2" and putting on weight distro bars pretty darn tight changed ride height by only ~1/8". Therefore weight distro bars don't effectively counter rear sag. Note tho that weight distro bars shift do more weight when the rig porpoises so they still fight that pretty well.

Click to expand...

Your bars are pointing up whereas they should be parallel to the trailer frame. Regardless I agree with the overall statement. I find where WD bars shine is in removing bounce from dips in the road.

toofart said:

Your bars are pointing up whereas they should be parallel to the trailer frame. Regardless I agree with the overall statement. I find where WD bars shine is in removing bounce from dips in the road.

Click to expand...

The hitch allows small adjustments to ball height by allowing the ball to tilt back and down. I was playing around with this to get another inch of adjustment. When the ball is tilted, the anchor points of the weight distro bars adopt an angle too.

I don't think it matters what angle the WD bars are at, only that they are fastened good and tight so a bending movement is applied

I might check with the Chrysler tech team before I started to worry about coolant temps. Modern diesel engines are starting to run much hotter to increase efficiency. By lowering the coolant temp, you may be leaving some MPGs and power on the table.

RangerGress said:

We disagree about the anti-freeze. A 25% solution will cool better than a 50% solution. Pure water actually works quite well, better if a wetting agent, like WaterWetter is added tho. It does not take much wetting agent to do the job. Wetting agents reduce surface tension.

It does have an oil cooler. Has to, it's a turbo. Oil temp wasn't a big deal tho. Oil will happily run at higher temps then coolant normally would.

We disagree about the louvers too. No way the louvers would have been trying to keep the coolant that hot. Sure, 224deg coolant isn't a crisis, but it's a little above the normal range also.

Click to expand...

Well, we can disagree all you want, but you need to talk to your chrysler tech and se how hot it is designed to run, as in favor of better emissions, ALL engines are being intentionally run hotter, diesels included. Most cars nowadays don't even kick the fans on till 220 deg or so.

And part of the reason they put the louvers ON the trucks was to cut down on drag from air moving thru the radiator & under the vehicle when it wasn't needed....IE, when the coolant was hot enough. That can indeed control temp in the radiator.

And I never said 25/75 wouldn't work, I just doubt it will work any better, and it may even be worse, especially if the PCM is intentionally keeping the temp up high for emissions. I DID say, pure water or pure antifreeze doesn't work as well as when they are mixed.


I've never had a vehicle do better with just water than a mix, and I have opwned over 20, from stock 4 bangers to a tweaked 12v cummins to a 750 hp N/A V8 that was street driven.

Before I went trying things to cool things down, I'd make sure it isn't supposed to be that hot first. And don't tell your dealer what you are doing, or you'll likely lose some warranty.

Improving the heat xfer capabilities of the coolant won't cause the engine to run too cold, that's what the thermostat is for. It doesn't just open once the engine is warmed up, it dynamically adjusts coolant flow to attempt to keep the coolant at a spec'd temp.

Re. Chrysler tech. Mechanics gain lots of skills thru experience and repetition. But "why" questions are often not their strong suit. They are not Ram engineers. In fact, they rarely have any background in the hard sciences so have little grasp of heat, chemistry, electricity, materials, solid mechanics, etc.

If you want a transmission changed a mechanic can do it in an hour and it takes me 6hrs even on a car that I've done it multiple times on. But if the issue is heat xfer, for example, the mechanic doesn't have the fundamentals.

Often it's hard to even trust the official word from the OEM. They have lot of competing interests other then just engineers. The decision making table has 2 guys from Marketing, 2 lawyers and 3 accountants. And 1 engineer. Consider the OEM specs for alignment that cause cars to handle like understeering pig.

Every assertion in the hard sciences should be mistrusted unless the person can explain the basis for the assertion.

All I can say on the matter is do what ever you please. It's your vehicle. Only thing I hope for is no crying and ******** when something gets effed up and they refuse to repair because of something you did.


Sent from my iPhone using Tapatalk

RangerGress said:

Improving the heat xfer capabilities of the coolant won't cause the engine to run too cold, that's what the thermostat is for. It doesn't just open once the engine is warmed up, it dynamically adjusts coolant flow to attempt to keep the coolant at a spec'd temp.

Re. Chrysler tech. Mechanics gain lots of skills thru experience and repetition. But "why" questions are often not their strong suit. They are not Ram engineers. In fact, they rarely have any background in the hard sciences so have little grasp of heat, chemistry, electricity, materials, solid mechanics, etc.

If you want a transmission changed a mechanic can do it in an hour and it takes me 6hrs even on a car that I've done it multiple times on. But if the issue is heat xfer, for example, the mechanic doesn't have the fundamentals.

Often it's hard to even trust the official word from the OEM. They have lot of competing interests other then just engineers. The decision making table has 2 guys from Marketing, 2 lawyers and 3 accountants. And 1 engineer. Consider the OEM specs for alignment that cause cars to handle like understeering pig.

Every assertion in the hard sciences should be mistrusted unless the person can explain the basis for the assertion.

Click to expand...

So you want a PhD to work on your truck? I hate to imagine what the labour costs would be.

Two Dog said:

So you want a PhD to work on your truck? I hate to imagine what the labour costs would be.

Click to expand...

Nope. My point was only that when a person asks "why", they shouldn't buy into the answer unless the physics behind the answer gets explained. People have all sorts of silly ideas why this or that happens. Just because a guy means well, doesn't mean he knows what he's talking about.

I am very intrested in what axle ratio you have in your ecodiesel ?

3.5 or 3.9 as the full load Laramie Crew I tested seemed to be running out of breath at 60 on a freeway 'on ramp'

my test drive was only a couple of miles so there is no hard science in my opinion but I am sure interested in what others have to say on the subject of axle ratios in the 3 liter diesel

twooldfarmers said:

I am very intrested in what axle ratio you have in your ecodiesel ?

3.5 or 3.9 as the full load Laramie Crew I tested seemed to be running out of breath at 60 on a freeway 'on ramp'

my test drive was only a couple of miles so there is no hard science in my opinion but I am sure interested in what others have to say on the subject of axle ratios in the 3 liter diesel

Click to expand...

3.55 on 20's. Unless I was towing up mountains I wouldn't get the 3.92. The tranny is perfectly capable of putting the engine in it's rpm comfort range.

The little engine did darn well. 15yrs ago the big diesels owners were happy with the 420ftlbs we're getting out of this little Italian.

I've never named a vehicle before. I might have to name the truck Valeria, after a smoking hot Italian tourist I dated the summer after college. Wow, what a summer that was.

Might neglect to tell the wife about that tho.

Apparently our turbo is watercooled and the tstat doesn't fully open until 222deg.
2014 Grand Cherokee Eco Diesel - Page 12 - Airstream Forums

If that's accurate then my coolant temp wasn't that high after all.

RangerGress said:

Apparently our turbo is watercooled and the tstat doesn't fully open until 222deg.
2014 Grand Cherokee Eco Diesel - Page 12 - Airstream Forums

If that's accurate then my coolant temp wasn't that high after all.

Click to expand...

People who were doing the same testing as you were with the ecodiesel grand cherokee's were seeing about the same numbers as you, so that seems accurate.

Obviously designed to run at those temps by the engineers. As long as it has adequate cooling capacity to control it once therm is open, I wouldn't worry about it.

I decided how to mount the air nozzle for the Airlift1000's. There's a couple holes in the receive that are about the right size.

RangerGress said:

-Towing mpg. Went for a 25mi test tow on a flat freeway at 64mph. 14.1mpg. For perspective, my 2000 F-250 diesel would have gotten 13-13.5. My old 2006 F-150 5.4l would have gotten 7mpg.

Lessons learned. I had hoped to get an honest 15-16mpg so this was disappointing. The diesel in the F-250 is regarded as one of the finest diesel engines ever put into a pickup and clearly it's a hard standard to beat.

Click to expand...

I am very impressed with this personally. 14 MPG towing is a pretty darned good number for a 'light duty' truck. The big difference is that empty, the ED will reward you with mid-high 20s MPG, something a PowerStroke would not see (not in stock form, anywho)

You might look into getting the Ram ST (open mesh) grill for more airflow.
That being said, I don't think your temps are anything to be concerned with.

Sorry to dredge this up, but one reason nobody has stated not to change the mix in your cooling system is because it also changes the BOILING point, not only the freezing point. More water- easier to boil over. The coolant temp in these trucks handles a lot more than just cool the engine. Keeps the transmission temp in the optimal range, oil, everything. Oil absorbs heat as well, and that is also part of the design- the oil and coolant are designed to keep that engine in the sweet spot for temps. If it's running too hot, you're going to know it. The temps listed wouldn't alarm me at all.