Ram 3.6 Towing

[supton]

It's a bit of a long video, but the TFL guys take the same 7k trailer up the Ike, using a Hemi and then a Pentastar, for a real A/B comparison.



Few thoughts:
-7k at altitude, wouldn't want to do that very many times with that Pentastar. 5k on level ground, once in a while, not a problem.
-the Pentastar was flat out in spots and could not hold 60mph in a couple of sections. Squinting one's eyes though and it sounds like 300hp was the magic number to maintain 60mph for the weight and grade.
-that 8 speed might need tighter gear ratios... It's a nice great spread but at high rpm it's still some large jumps, and possibly too large.
-I don't know if I "trust" the mpg readout. But both trucks indicated 4.7mpg towing up the Ike.
-If that's remotely true, that implies to me that I've been assuming something wrong all these years: a slow rpm motor should be more efficient, on the basis of allowing more time in the cylinder for expansion of hot gasses. Apparently the 3.6 at high rpm is just fine.
-Yes, I get that old school V6's were not efficient at high rev's, they were outside of their powerband (trading engine torque for gear multiplication, running at high rpm to get the last hp to get the job done).
-I wonder... is an engine most efficent at turning fuel into mechanical energy at torque peak, give or take? and once torque nose dives, then efficiency drops? If so, does that mean an engine with a flat torque curve is relatively efficient over that entire flat torque curve?

Something that I don't get: if you fast forward to 14:21, you will see engine temp at 231F. [They don't show what the Hemi was running at.] That is hot! Now, both engines are doing the same amount of work, and burning the same amount of gasoline--so why was the V6 running that hot? Both had the same amount of gasoline going into them, and doing the same amount of work. Ergo, it says to me that the same amount of waste heat should have been going into the coolant.

So... I wonder:
-does the Pentastar get a smaller radiator?
-does the Pentastar get a smaller water pump? Either of these two means it can't get heat out fast enough.
-or does the Pentastar have more heat into the cooling system by virtue of the integrated exhaust manifolds?

Anyhow. More fuel for the V6 vs V8 debates.

 

[SwampSurvivor]

I love watching the TFL towing videos. They really do test the truck AT the limit. I will say, I wasn't too big of a fan of the one where "Mr Truck" wouldn't rev the old 305 above 3000 RPM. I would like to see more older trucks doing it , too. There was a channel on youtube a while back that used to load 14K on a trailer and run up a 14% grade --- a 3.5 EB F150 out towed a 7.3 powerstroke. TFL also saw that if they held a 3.5 EB wide open they would have hit triple digit speeds so they had to let off.

231F is pretty warm, normally I wouldn't be concerned but the Pentastars seem to have a problem with warped heads. I could see that being a long term issue. I imagine the ecodiesel has a bigger radiator (parts lookup on rockauto has the 3.0 using a different radiator than 3.6)

With that said, I ran my 200k mile junkyard 5.4 all out up a hill here and on the scanner , it didn't get above 205F. But it has a mechanical fan and I tried to keep the revs below 4K ... because it was a 200K mile junkyard engine that was dropped in not even a week prior.

It does beg the question -- does one NEED to maintain the speed limit on these higher grades? Mine can pull a lot of hills at 45-50 with maybe 50% throttle, but 60 would be wide open and in a lower gear with more RPMs. I've always been more concerned with getting down the hill safely than up it quickly.

 

[demarpaint]

Interesting video. The Pentastar runs not, in fact the fan doesn't come on until 226F in mine [2016 JK Wrangler] unless the AC is on. I'm not sure how they programmed the PUG update with regard to when the radiator cooling fan comes on. But yes they run hot, scary hot for me. I did some mods to the hood vents, and remove the engine cover in the summer, it helps.

 

[Cujet]

235 (what I saw in the video) degrees is not a problem for a well designed system. A typical cooling system will "overheat" about 260 degrees. This is because water boils at a higher temperature under pressure. So with 16 pounds pressure held in by the cooling system "radiator cap" , the boiling point is about 260 degrees. There won't be a hint of a problem until then.

However, clearly the 6500 RPM, 235 degrees and 54 MPH is showing the limitations of the small engine choice.

For those with the V6, don't tow quite so much weight

 

[Delta]

Originally Posted by Miller88
With that said, I ran my 200k mile junkyard 5.4 all out up a hill here and on the scanner , it didn't get above 205F. But it has a mechanical fan and I tried to keep the revs below 4K ... because it was a 200K mile junkyard engine that was dropped in not even a week prior.


That is notoriously tough stretch of 81. Believe it or not you did better than the 2012 Ford Transit Connect I used to have as a company vehicle... There was another spot before you got into Wilkes-Barre that was kind of sketch too.

 

[supton]

Interesting! I always that 220F was bad-hot. Probably depends on where the temperature sensor is, and what will blow if pressure gets any higher. The fact that fans might not even turn on until 226F...

I agree, back off on the really big hills, and wind drag will come way down, leading to the engine having to do less work.

Been watching a few vids recently of the Ridgeline towing up to 5k (albeit not enclosed trailer) and it seems to handle it ok.

 

[ofelas]

Moral of the story - a pickup tows best with an inline-6

 

[Cujet]

It's nice to think that 6500 RPM won't damage an engine, but we must remember that inertia places the highest loads on reciprocating parts. So while damage won't occur with good designs, high RPM does markedly increase wear related loads. Con rod bearings experience far higher loads from inertia (rpm) than they do from boost. Same goes for valves, which slam down on the seats 54 times per second at 6500. This can increase valve face and seat wear (a common problem on high rpm engines) And of course, piston pins, pistons and rings. All subject to significant additional stress.

Interestingly, turbocharged engines with double their normally aspirated output do not exhibit double the con rod and con rod bearing loads (generally considered 14 pounds boost depending on design) This is due to the dense mixture taking more time to burn.

The highest risk is often in tension at redline or above, where insufficient designs have rod bolt stretch issues and eventual failure.

 

[Job]

Is there some happiness in being the first to the top of a mountain? Is everything a race these days? In the olden days trucks had less power and made it up all the grades jst fine on worse roads, just took a few minutes longer. Everyone is in such a rush these days to go sit somewhere.

 

[The_Nuke]

Originally Posted by supton
It's a bit of a long video, but the TFL guys take the same 7k trailer up the Ike, using a Hemi and then a Pentastar, for a real A/B comparison.

Few thoughts:
-7k at altitude, wouldn't want to do that very many times with that Pentastar. 5k on level ground, once in a while, not a problem.
-the Pentastar was flat out in spots and could not hold 60mph in a couple of sections. Squinting one's eyes though and it sounds like 300hp was the magic number to maintain 60mph for the weight and grade..

I am curious why the need to maintain 60mph on the road in question. If someone is hauling 7K lbs in a less than ideal driving situation, I would much prefer they forego trying to maintain some arbitrary speed limit set for non-trailer-towing vehicles and spend their energy on more important things...like trying not to wreck out, trying not to start fires, moving right when applicable to allow for passing, etc.

Originally Posted by supton
-that 8 speed might need tighter gear ratios... It's a nice great spread but at high rpm it's still some large jumps, and possibly too large..
The upper RPM towing experience might improve from differently spaced gears in the transmission, but they just integrated that ZF auto into the LX cars and RAM trucks a few model years back. It's not going to be replaced or significantly modified anytime soon. Gearing issues would have to be addressed by swapping out the rear-end with one that was higher/lower geared according to desired affects on final drive ratios.

Originally Posted by supton
-I don't know if I "trust" the mpg readout. But both trucks indicated 4.7mpg towing up the Ike.

Any time spent at WOT is going to drop the MPGs significantly. The more WOT time, the worse it's going to be. Having said that, I was always amazed at how efficient the 3.6L was in high RPM operation. Granted I never towed anything around other than my big butt.


Originally Posted by supton
-If that's remotely true, that implies to me that I've been assuming something wrong all these years: a slow rpm motor should be more efficient, on the basis of allowing more time in the cylinder for expansion of hot gasses. Apparently the 3.6 at high rpm is just fine..

I'm not sure what you're referring to with the expanding of hot gasses reference, the gasses' compression and expansion will be most directly affected by the movement of the piston (up/down). A slow RPM motor may not be any more efficient than a high RPM motor, it's all in how the motor is designed and built plus what kind of gears are used to transfer its power to the drive wheels, not to mention the type of load the motor is trying move/haul/pull.

Either way, I will go on record again as saying the 3.6L excels at high RPM operation efficiency in my experience. Now, my experience was with it in a Dodge Challenger (4K lbs) with the A5 trans and a 2.65 rear-end. That would be a terrible setup to try to haul a load in, and I would expect it to disappoint greatly if put to the same test here. But cruising at 70mph and suddenly executing a passing maneuver to overtake 2 to 3 cars in a row was a blast. I could that all day long during a 5 hour road trip and still pull 30 mpg for the trip.,

Originally Posted by supton
Yes, I get that old school V6's were not efficient at high rev's, they were outside of their powerband (trading engine torque for gear multiplication, running at high rpm to get the last hp to get the job done).
-I wonder... is an engine most efficent at turning fuel into mechanical energy at torque peak, give or take? and once torque nose dives, then efficiency drops? If so, does that mean an engine with a flat torque curve is relatively efficient over that entire flat torque curve?.

When you use efficiency, are you talking about the engine's Volumetric Efficiency? If so, yes, its largest VE will usually be the same RPM as peak torque, and after peak torque (max VE) is reached, continuing to raise the RPMs will be subject to the law of diminishing returns. It's best not to go too far beyond that unless it occurs at such a low RPM so as to be ineffective at accelerating the vehicle in question.

Originally Posted by supton

Something that I don't get: if you fast forward to 14:21, you will see engine temp at 231F. [They don't show what the Hemi was running at.] That is hot! Now, both engines are doing the same amount of work, and burning the same amount of gasoline--so why was the V6 running that hot? Both had the same amount of gasoline going into them, and doing the same amount of work. Ergo, it says to me that the same amount of waste heat should have been going into the coolant.

So... I wonder:
-does the Pentastar get a smaller radiator?
-does the Pentastar get a smaller water pump? Either of these two means it can't get heat out fast enough.
-or does the Pentastar have more heat into the cooling system by virtue of the integrated exhaust manifolds?.
This one would be my best guess for why it might have a propensity to run hotter than other engines in high load situations.

Originally Posted by supton
Anyhow. More fuel for the V6 vs V8 debates.


Having owned both the engines in the comparison (though not a pickup truck), I will say it's a fool's errand to debate the 3.6L vs. the 5.7L. There are too many other variables involved usually (vehicle weight, transmission, rear-end gearing, intended operation).to be able to effectively compare/contrast their operation. If I were making the run outlined in the video once per year, I would go with the 3.6L to save on gas most likely. If I were making it often, I would probably go with the Hemi to keep the maxed-out run time to a minimum on the engine in my particular vehicle. It always boils down to personal preference and view though, so the V6 vs. V8 is one debate I would venture to guess has never had even a single person defect from one side to the other, due to the debate itself. Kinda like politics and religion - it doesn't matter who's right and wrong, it will never be resolved in favor of one or the other.

 

[supton]

Originally Posted by The_Nuke
Originally Posted by supton
It's a bit of a long video, but the TFL guys take the same 7k trailer up the Ike, using a Hemi and then a Pentastar, for a real A/B comparison.

Few thoughts:
-7k at altitude, wouldn't want to do that very many times with that Pentastar. 5k on level ground, once in a while, not a problem.
-the Pentastar was flat out in spots and could not hold 60mph in a couple of sections. Squinting one's eyes though and it sounds like 300hp was the magic number to maintain 60mph for the weight and grade..

I am curious why the need to maintain 60mph on the road in question. If someone is hauling 7K lbs in a less than ideal driving situation, I would much prefer they forego trying to maintain some arbitrary speed limit set for non-trailer-towing vehicles and spend their energy on more important things...like trying not to wreck out, trying not to start fires, moving right when applicable to allow for passing, etc.


Not getting run over by other traffic, I'd bet, along with getting there all the sooner.

Quote
Originally Posted by supton
-that 8 speed might need tighter gear ratios... It's a nice great spread but at high rpm it's still some large jumps, and possibly too large..
The upper RPM towing experience might improve from differently spaced gears in the transmission, but they just integrated that ZF auto into the LX cars and RAM trucks a few model years back. It's not going to be replaced or significantly modified anytime soon. Gearing issues would have to be addressed by swapping out the rear-end with one that was higher/lower geared according to desired affects on final drive ratios.


Not sure I agree. there was a point where he downshifts, wanting a bit more rpm, but the trans wouldn't allow it. And I want to say it was in 3rd gear, "needing" 2nd gear. Usually gear ratios tighten up as you go up, but here was a case where closer spacing down low might have yielded a 500rpm bump.

Quote
Originally Posted by supton
-I don't know if I "trust" the mpg readout. But both trucks indicated 4.7mpg towing up the Ike.

Any time spent at WOT is going to drop the MPGs significantly. The more WOT time, the worse it's going to be. Having said that, I was always amazed at how efficient the 3.6L was in high RPM operation. Granted I never towed anything around other than my big butt.


Well, yeah... My point was, both motors returned the same mpg. Same work being done, but same mpg. As you'd expect. But over the years many will said the V6 will burn more gas because of high rpm, or somesuch.

Both motors did the same job, nearly the same speed, and returned the same fuel cost. Impressive I think.

Quote
Originally Posted by supton
-If that's remotely true, that implies to me that I've been assuming something wrong all these years: a slow rpm motor should be more efficient, on the basis of allowing more time in the cylinder for expansion of hot gasses. Apparently the 3.6 at high rpm is just fine..

I'm not sure what you're referring to with the expanding of hot gasses reference, the gasses' compression and expansion will be most directly affected by the movement of the piston (up/down). A slow RPM motor may not be any more efficient than a high RPM motor, it's all in how the motor is designed and built plus what kind of gears are used to transfer its power to the drive wheels, not to mention the type of load the motor is trying move/haul/pull.


Conversion of gasoline (chemical) energy into mechanical energy. Power out divided by power in, or a similar ratio. Usually we boil it down to miles per gallon, with all other factors held the same (which in this case, they were--same size truck, same load, same trailer). The hot expanding gasses have less time to expand in the cylinder--at 6k, it's half the time at 3,000rpm.

But that doesn't seem to matter.

Quote
Either way, I will go on record again as saying the 3.6L excels at high RPM operation efficiency in my experience. Now, my experience was with it in a Dodge Challenger (4K lbs) with the A5 trans and a 2.65 rear-end. That would be a terrible setup to try to haul a load in, and I would expect it to disappoint greatly if put to the same test here. But cruising at 70mph and suddenly executing a passing maneuver to overtake 2 to 3 cars in a row was a blast. I could that all day long during a 5 hour road trip and still pull 30 mpg for the trip.,

Originally Posted by supton
Yes, I get that old school V6's were not efficient at high rev's, they were outside of their powerband (trading engine torque for gear multiplication, running at high rpm to get the last hp to get the job done).
-I wonder... is an engine most efficent at turning fuel into mechanical energy at torque peak, give or take? and once torque nose dives, then efficiency drops? If so, does that mean an engine with a flat torque curve is relatively efficient over that entire flat torque curve?.

When you use efficiency, are you talking about the engine's Volumetric Efficiency? If so, yes, its largest VE will usually be the same RPM as peak torque, and after peak torque (max VE) is reached, continuing to raise the RPMs will be subject to the law of diminishing returns. It's best not to go too far beyond that unless it occurs at such a low RPM so as to be ineffective at accelerating the vehicle in question.


IIRC VE is horsepower per cubic inch, not power out / power in.

Quote
Originally Posted by supton

Something that I don't get: if you fast forward to 14:21, you will see engine temp at 231F. [They don't show what the Hemi was running at.] That is hot! Now, both engines are doing the same amount of work, and burning the same amount of gasoline--so why was the V6 running that hot? Both had the same amount of gasoline going into them, and doing the same amount of work. Ergo, it says to me that the same amount of waste heat should have been going into the coolant.

So... I wonder:
-does the Pentastar get a smaller radiator?
-does the Pentastar get a smaller water pump? Either of these two means it can't get heat out fast enough.
-or does the Pentastar have more heat into the cooling system by virtue of the integrated exhaust manifolds?.
This one would be my best guess for why it might have a propensity to run hotter than other engines in high load situations.

Originally Posted by supton
Anyhow. More fuel for the V6 vs V8 debates.


Having owned both the engines in the comparison (though not a pickup truck), I will say it's a fool's errand to debate the 3.6L vs. the 5.7L. There are too many other variables involved usually (vehicle weight, transmission, rear-end gearing, intended operation).to be able to effectively compare/contrast their operation. If I were making the run outlined in the video once per year, I would go with the 3.6L to save on gas most likely. If I were making it often, I would probably go with the Hemi to keep the maxed-out run time to a minimum on the engine in my particular vehicle. It always boils down to personal preference and view though, so the V6 vs. V8 is one debate I would venture to guess has never had even a single person defect from one side to the other, due to the debate itself. Kinda like politics and religion - it doesn't matter who's right and wrong, it will never be resolved in favor of one or the other.

The debate will rage eternal (at least until Musk has us all driving electric trucks), but I do like engaging in them, time to time. Sometimes I learn new things. I try to keep my opinions in check against reality--sometimes reality changes (gas motors have come a long ways in my lifetime). V6 used to mean cheap truck that can barely get out of its own way.

Twenty years ago, thirty years ago... none of this would be imagined. Today's V6's and today's transmissions hold their own against what used to be sold back in the day.

 

[SwampSurvivor]

Originally Posted by Delta
Originally Posted by Miller88
With that said, I ran my 200k mile junkyard 5.4 all out up a hill here and on the scanner , it didn't get above 205F. But it has a mechanical fan and I tried to keep the revs below 4K ... because it was a 200K mile junkyard engine that was dropped in not even a week prior.


That is notoriously tough stretch of 81. Believe it or not you did better than the 2012 Ford Transit Connect I used to have as a company vehicle... There was another spot before you got into Wilkes-Barre that was kind of sketch too.


What's funny is I did get passed by a full sized Transit pulling a jeep.

That part of 81 is probably the worst part from the Canada border until you get down into TN/NC

 

[The_Nuke]

Actually, a more interesting video to me would have been to throw in a truck with the 3.6L's predecessor, the much-maligned 3.5L, to also compare how it does. I get it, that's impossible since there aren't any modern trucks with that 3.5L in them, and no one except me would even care about the results, but i'm telling you, that 3.6L was leaps and bounds above the 3.5L in terms of, well...everything. I think a comparison in this sort of test would be just the thing to illustrate how much distance the engineers covered in replacing the 3.5L with the 3.6L.

 

[supton]

3.5? I thought it was the 3.7... which was based on a cut-up 318.

TBH, they probably are running that test right now. It's just that the truck still hasn't made it.

I thought GM was shooting itself in the foot when they kept saddling the 4.3 and 4.8 with their old 4AT while only the 5.3 got the much improved 6AT. They were milking the last pennies out of that engineering.

 

[The_Nuke]

Originally Posted by supton
3.5? I thought it was the 3.7... which was based on a cut-up 318.

TBH, they probably are running that test right now. It's just that the truck still hasn't made it.

I thought GM was shooting itself in the foot when they kept saddling the 4.3 and 4.8 with their old 4AT while only the 5.3 got the much improved 6AT. They were milking the last pennies out of that engineering.


The LX cars got the 3.5L, but the trucks may well have had the 3.7L instead.

All I know, is sticking that 3.5L in a 4K lb car like the Charger/Challenger and saddling it with 2.xx gears like they did was a travesty. That's the only car I ever drove where I was in constant danger of getting a parking ticket while driving!

"Uh, no officer, I am NOT illegally parked, as I am actually moving forward at this very moment.
I know it may not look like it, but I am in fact right in the middle of a 0-60 mph run right now!!!"

 

[JTK]

I own a 2017 Ram 1500 pentastar 4x4 with the quad cab, 8spd trans and 3.21 gears. Per my truck's configuration it can only tow 4440 lbs. I don't own a thing to tow and mostly haul air as we say on BITOG. LOL!

What's funny is my brother just purchased the same truck, but a brand-new 2019 "classic". For a whole $95, it has the 3.55 gear ratio option which boosts the towing capacity to 7420. The pentastar and 3.55 combo is bit harder to find, but they're out there. Just have to put "3.55" in the search bar when searching a dealer's inventory, or they're about impossible to find because it's a stand alone option. He wanted the 3.55s because he does some boat towing. Nothing huge. Maybe 3-4K lbs.

You have to keep in mind the Pentastar powered Ram 1500s have the lower torque handling capability 8HP45, where the Hemi powered Rams have the 8HP70.

Like said, both engine and trans run hot by design. I've read that the ATF danger zone is anything above 240F for these 8spds. The ATF cooler is integrated into the A/C condenser like most FCA vehicles. There is an ATF heater/heat exchanger that is mounted on the outside of the 8spds. The electronic 3-way coolant valve either sends coolant to the heater core, trans heater or any combo of the two. I've found with our recent single digit ambient temps, if the heater is on full blast, my ATF temp will run in the 120-160F range after a 40 mile drive. Turn the cabin heat down and you can watch the ATF temp rise some. In the summer, on a super humid 90F+ day with the A/C cranking, I've seen engine coolant, oil and ATF temps in the 200-215F range after a lot of mixed driving.

The E-fan looks huge and moves a serious amount of air. In terms of radiator size? Not sure if the pentastar and hemi share the same or not.

 

[demarpaint]

I would like to see the Ram equipped VM diesel vs. the Hemi. If anyone even thought for a second the V6 was going to do well against the Hemi they were dreaming. Having said that the Pentastar still impressed me.

 

[supton]

Originally Posted by demarpaint
I would like to see the Ram equipped VM diesel vs. the Hemi. If anyone even thought for a second the V6 was going to do well against the Hemi they were dreaming. Having said that the Pentastar still impressed me.

TFL did test the Ecodiesel. It was slow. They seemed surprised, but... Surprise! 240hp is still 240hp, regardless of how many "torques" it has.

I don't think it was apples to apples, might not have been same trailer and load.

Of course, the ED wasn't turning 6k, and I don't remember the mpg but it had to have been better.

I'm quite frankly quite impressed with the Pentastar. If anything, I bet if you wore one out towing... it'd cost pennies to drop a new motor in. Fiat must be making a million of them a month now.

 

[ragtoplvr]

In the not so distant past, the first ford 6.9 diesels made 175 horsepower. The passes all have slow lanes, and you will be in them. The world did not stop and no harm was done except to pride. just pull those passes at the speed of the semi at about 30/40ish ad you will be just fine, heads will not warp and kittens will not die. Use that $1000 plus you save over the 5.7 to take more vacations.

Rod

 

[supton]

Originally Posted by ragtoplvr
In the not so distant past, the first ford 6.9 diesels made 175 horsepower. The passes all have slow lanes, and you will be in them. The world did not stop and no harm was done except to pride. just pull those passes at the speed of the semi at about 30/40ish ad you will be just fine, heads will not warp and kittens will not die. Use that $1000 plus you save over the 5.7 to take more vacations.

Rod

The weird thing is, back when I was on Tundra forums, they'd all recommend you to spend the extra grand and get the 5.7 over the 4.6, so you wouldn't have to slow down and so that no kittens would die. And better resale value.

TBH if I had to buy a truck today I'd very much be looking at a Pentastar with coil springs and 3.55's. It'd do what I needed (or wanted). Not sure about 2019's (new fangled electric start blah blah blah) but I think I'd be content otherwise. The Ridgeline is close but while looking today I found out that you can't force it to hold 1st gear (or prevent from shifting above 2nd, or 3rd) and I don't think I care for that kind of programming.