High Temp Towing Uphill

[SD Rebel]

This is a brand new truck with a spotless radiator. I again forgot to notice the oil temp. I saw the FTL video and they were screaming up a grade similar, or worse, then the one I climbed. They were pulling 10,000 lbs, whereas I'm pulling 6800. I should not be hitting 248!

Yup, that was my initial assumption. Based at least on TFL's results, you should not be at that high a temp. You are towing less weight at a lower incline for less time. The one difference is their elevation, not sure how that factors into it. But considering their high elevation saps power, it should make it even harder for them.

 

[Oroman]

Is it remotely possible that I have a coolant temp sensor recording too high at the high end? I assume that the gauge position is based on the sensor reading?

 

[Oroman]

Also to mention that my truck build sheet shows the truck came with:
Heavy duty engine cooling
Heavy duty transmission oil cooler
Engine oil heat exchanger

 

[devildodge]

All HEMI engines come standard that way.

If you do not get the overheat light...which is set 15 degrees before the 265 degree actual overheat then you are fine.

What grade fuel are you usin?. Did you select a lower gear? Have you checked your fluid level? Have you made sure a shopping bag or other litter or dirt is not blocking the radiator?

You are near Gross Combined. Your truck is working to climb a hill. Then only way I would spend another second concerning myself is if when the grade is over...the truck doesnt cool back down.

 

[Buz]

Not a criticism here, just curious, but how does outside ambient temp really effect operational temp?

Agreed if he was talking about oil or trans temp.
But he's talking about coolant temp. A difference in ambient temps of 25 degrees may have an actual impact on coolant running temps.

 

[SD Rebel]

Agreed if he was talking about oil or trans temp.
But he's talking about coolant temp. A difference in ambient temps of 25 degrees may have an actual impact on coolant running temps.

I don't honestly know, I'm not saying it isn't the case, but I haven't found anything to confirm it.

The reason why I mention it is because I was in 115F ambient temp and my truck's temps were the same as they were at 50F ambient temp. Whether that was cruising at speed or very slowly climbing a off-road obstacle and idling with full A/C on. My truck didn't react any different with temps. I mean ambient temp at 115F is still way below the operational temp of 215-220F of my coolant, so that's why I don't see how it should effect anything other than air intake charge pressures, so the motor should be making less power in that situation.

Now of course I wasn't towing 7,000 lbs up a hill, that could be very different. The only things I've found about ambient air temp's effect on operational vehicle temps is a college paper on PDF that shows no noticeable effect. However it didn't take into account things like towing or heavy use.

 

[Oroman]

Nothing blocking radiator. Cruise control was off. I locked into 4th gear for most of the climb .... 3rd gear for the last steepest portion. Coolant fluid 1/3 above min level...assume that is OK. Using your usual unleaded fuel...should I consider higher grade?. If light goes on at 250, but 265 is "actual" overheat, should I still pull over and let engine cool just before 250 (let's say I had more hill to climb)? It sure looks like the gauge would be pegged before 265? What about the comments on the TFL video? 1500 HEMI pulling 10K up longer grade only got up to 240?

 

[devildodge]

You have 3.21 gears correct.

I am no expert. But I would have towed the whole stretch in third. Possibly 2nd. I habe no experience with the 8 speeds.

On my way home on Sunday I was thinking about this post.

I locked my 392 Hemi in 2nd gear and stayed in it for the whole trip across the leaps and dips here in PA.

40 and 45 mph roads. Even in second I had to hit 55 to get above 3500 rpms. These HEMI engines need to be at about 4500 to be in the power.

So lugging along in 4th gear...alot of heat is being made with little help to the task.

Just my thoughts.

Truck is performing the task...the number just looks scary.

I have said before. And this is just an example of numbers.

A guy buys a HEMI. He drives around town and the truck barely ever sees RPM over 2k

He hooks up his trailer and tries to stay under 2k. And then he curses and says he should have bought a Diesel.

But then he locks the truck in 2nd gear. Brings that HEMI up to 4000 RPM and he is hooked on how well it tows.

5.7 l Hemi 395 Horsepower at 5600 rpm
410 Torque at 3950 RPM

 

[devildodge]

89 octane may be needed to rum that hill. 87 may be causing the need for more fuel causing higher temps. Just a thought. If you are Running 89 then I guess that isnt it.

Then I also see people at elevation needing a lower rating. So maybe vice versa.

 

[Oroman]

OK I'll try higher octane next time. I must say I was not up to 4000 rpm..I was around 3000 - 3500. Can you explain how running at 4000 will help mitigate engine heat accumulation?

 

[LoNeStAr]

To get peak performance from the Hemi the manual says to run 89 octane

 

[SD Rebel]

OK I'll try higher octane next time. I must say I was not up to 4000 rpm..I was around 3000 - 3500. Can you explain how running at 4000 will help mitigate engine heat accumulation?

Definitely use 89 octane to get the best power/mpg on the Hemi. I think he means 4,000 rpms to get into the ideal powerband, the engine will lug more if too low an rpm, creating more friction and heat. Though your engine should be picking the best gear to be in while in tow/haul mode.

 

[silver billet]

At the risk of starting another octane war... agreed with other posters here, when towing, do not try to save a few bucks on gas, these hemis absolutely need 91+ octane as you can see if you start data logging your ECU. When coasting around in town, it's less obvious, but feeding it 87/89 is like trying to put in a full day of work with milkshakes and celery sticks.

As for the tow haul mode, I've found in my towing that it doesn't always pick the right gear, for me. I'd much rather rev a little higher and feel that there is power left in the pedal without a downshift, than having it lug and knowing that another slight dip in the pedal will cause a downshift. If you have that feeling, that a slight dip in the pedal = downshift, then you're next door to lugging it; if you're going up a hill like that, just downshift it manually.

If you're maintaining freeway speeds (63 mph), I tow my trailer in 6th and rev about 2300 rpms. Transmission would sometimes upshift, but I don't let it, and gear limit to 6.

When going up a hill, right before the hill I'll force a downshift so that the truck is already making more power before it hits the hill, sometimes gaining a bit of speed in the process, giving me a buffer to climb up the hill. Transmission won't automatically downshift until it is already working harder than it should be and losing a bit of power.

 

[LoNeStAr]

Hey I can work the whole day on milkshakes and cheeseburgers

 

[devildodge]

First. When towing, use 89 octane. Especially in the heat. In the cool, the air is more apt to help create some power and in the heat the air is apt to hinder power. If that makes sense. (I sure wish sometimes we had a clubhouse to meet in to discuss topics...much easier to get a point across) I see there is a thread now saying 93 is helping some...not sure about that...but may be worth a try sometime.

Do you have a large grade near you?

If so try this experiment. Go to it. Climb it with just the truck in drive I at 55 mph. Record (or remember what gear it used.)

Now go back up it in 3rd gear. Notice how you can get to 55 and leave out of the throttle and then can actually increase speed with very little throttle input.

This is why it will run cooler in a lower gear in the Powerband. In a higher gear you have to dump more fuel to keep the RPM momentum. In a lower gear you can dump less fuel and therefore create less heat.

@silver billet nailed the explanation above.

Tow/haul pics the best gear based on fuel mileage and comfort.

Selecting the gear yourself allows you to just select for power.

My 99 V10 Magnum with 5 spd and a 3rd pedal could tow most every hill in 4th...even 5th...but put that truck in 3rd and it was a blast to throttle up the hill.

That said...also in 3rd...i knew I would not have to downshift for a turn...in 4th or 5th I would.

Does that make any sense? I hooe so.

 

[RunsWithBeer]

Why would you manually choose a gear rather than keep it in "automatic" and let the ECM figure out the best gear for the load / conditions?

 

[devildodge]

Why do I? Because I tow with a manual more often and I get to make the decision.

I feel that the computer does not pick the best gear...just the best gear for the program.

I feel picking 3rd or even 2nd allows me to feel more in control and ready for the next hill either going up or going down.

Picking a lower gear allows you to start adding throttle without worry of a down shift or upshift and lets me have momentum for a hill...which here in PA is going to hace a sharp turn in it and most likely have a downhill drop.

I like picking my gear because the computer can not see the terrain I see.

If I was towing out west where it is flat and then you start to go up...maybe I would justblet the computer do it. But here in PA you can be going up to a turn that then goes down to a turn. That then goes up.

That is why i do it.

The main reason being it keeps me at 3000 RPM FOR BOTH POWER AND ENGINE BRAKING.

try selecting a low gear once...and then romp around town. You will see how it stays in the power and you actually have a gas pedal sweep you can use.

 

[JJRamTX]

Why would you manually choose a gear rather than keep it in "automatic" and let the ECM figure out the best gear for the load / conditions?

I pick one just so it doesn't hunt when I don't want it to like passing a semi on a grade or slowing down due to a vehicle in front of me but not wanting to let it shift to a higher gear.
And on the other Octane note, 85 is what is regular unleaded here in Colorado which is what I used the last 2 times I have done the Ike Gauntlet, no issues.

 

[Oroman]

I just read a summary of SAE J2807. The towing capacities listed by truck manufacturers must be established using this standard starting several years ago. The grade test component is called Highway Gradeability and requires the truck to pass the following test criteria:
Climb the 11.4 mile Davis Dam Grade (5% throughout; 3000 ft elevation rise) at minimum 40 mph during a 100 degree; day with AC on full blast. There must be no cooling warnings or check engine warnings to pass this test.

There is no way in heck my truck would pass that criteria without hitting 250 degrees or more! I was at 248, 2 degrees from a warming light after just 6 miles. It's ridiculous to think I could have gone another 5 miles without overheating. Something is wrong with this truck for sure. I'm taking my truck and SAE J2807 in to the dealer for an autopsy.

 

[LoNeStAr]

Out of curiosity what temp do you think your truck should have been running temp wise?