Interested in the 6.4, which years?

[SouthTexan]

SouthTexan, how many times have I linked this and you never read it Ram reengineered the block and heads for the HD motor, including the coolant jackets in both. Now maybe your right and it's still heating up, but it's not the same block the cars use(except the Hellcat). Plus to my knowledge most focus in modern day has been more around monitoring cylinder head temps. Maybe Ram/FCA doesn't. Would also be very curious to see how oil temps figure into the equations.

IMO, the motor is very sensitive to octane as you suggested. I could even feel a difference in how the truck ran between 87 and 89 in come cases. When towing I always bumped up the octane regardless.

Sorry, I didn't fully read that the last time you posted it since the post was meant for someone else. From what I gathered from that article it seems that the blocks are the same for the most part besides "improved coolant jackets". That type of stuff was marketing speech for "a few more holes machined into it" back when I used to work for the manufacturers. Not saying that is the case here.

I knew the heads were not the same. There is no way they could be or you guys would be popping heads left and right due to the heat of a trucks duty cycle.

I think they should have done like Ford did with the 6.2L by starting from scratch making a new engine made for an HD truck instead of just making a 6.4L fit into the block dimensions that was originally for a 5.7L and modifying the coolant jackets. That is a lot to cram into such a space. Larger block dimensions would mean larger coolant jackets which means that the limp mode would probably be non existent. Not only that, but I would wager that the power output would have been considerably higher. I think the 6.4L is held back power wise and that it is mainly due to heat management and detonation. If the block was larger and could easily manage the heat in a truck application, I have no doubts it would be in the 440-460 hp range.

I also think they should have mated a better geared transmission specifically geared for a gas engine instead just putting a downgraded transmissions geared for a diesel with it.

 

[drittal]

I have been in these threads that talked about the limp mode and I have never seen anyone say that it will happen on any incline approaching 6% or 7%.

Here ya go... and it goes back a few posts. Basically he thinks the 6.4 had the same performance on the Davis as the Ike because similar grade.

Look at the difference in grades, they don't have to run the davis dam grade to cert and can use a trailer simulating the dynamics. Its all about the grade and different tests pertains to the grades. The davis dam grade was used so the customer could put some kind of physical reference to what the test was to represent, it also have ambient temp limits. Min of 100f I beleive. It involves multipule stop go on grades that has Min speed requirements. Read up on the test...

Ford Employs Virtual Tow Testing for Super Duty - PickupTrucks.com News

Now back to you...

Knowing what I know about engines, I can tell you that it isn't a "high altitude only" thing or dependent upon a certain grade. There is no sensor on these trucks that senses altitude telling the truck to kick in limp mode. That is not how sensors on the engines or ECM mapping works.

How it does work is that the ECM is programmed to throw the truck into limp mode if certain criteria like engine oil temp or transmission oil temp are within certain ranges. This could happen at any altitude and any grade. It could happen at 600 ft above elevation pulling a load through a long hilly area that constantly goes up and down making the engine and trans work hard -IF- the temps get to the certain range that the ECM is programmed to put the truck in limp mode. It is not dependent on altitude or grade and is only dependent on how hot the temps get.

I myself have always wondered what causes the truck to go into limp. I know it is either the trans or engine getting hot, but which one is triggering it is still up in the air. My guess would be the engine for a few reasons. One being is that people have been pulling heavy loads with the 66RFE in the 5.7L for a long time without this limp mode issue ever being mentioned which leads me to believe it is not the transmission temps triggering it.

I disagree, I think it is a number of factors, not just temp. I think it's more about sensing shifts from 1-2 and 2-1, WOT and high RPM over a certain time period.

Why? When I experiences the gear hold I was having no problem slowing down for 25mph hair pins then accelerating out of them at ~93% of my GCWR. The truck would shift into 2nd, but not for long as I'd have to slow down for the next hair pin. 5 or 6 hair pins and I went into gear hold. EOT was 253 at this point, but wasn't even at 3/4 gauge. Even furthur from the red. Immediately all temps across the board dropped to just above 1/2. IIRC EOT went to 235. And it stayed there. The truck maintained gear hold after the hairpins stopped. Stayed in gear hold after all temps dropped. It did not come out until the grade lessened and the truck was able to accelerate up to highway speed.

I feel the truck is programmed not to let you out of gear hold until you can maintain 4200 rpm with a certain % of throttle.

The second reason would be the size of the 6.4L itself. After doing some research I found out that the 6.4L essentially uses the same block as the 5.7L but with a 4.4 mm larger bore and a 3.71 mm longer stroke. The coolant jackets on the block were designed to cool a 5.7L and cutting more bore out into the same block along with an increased stroke might be too much for those coolant jackets to properly cool the engine in certain situations with a constant heavy load. The cooling may be fine for the car application that the 6.4L was designed for and for most truck duty cycles, but not for very rare truck duty cycles with constant heavy load. This may also be why Ram changed the fuel to mid grade in 2015 seing that the engine running hotter under certain heavy loads may cause predetonation. This is just my guess though based on what I have read.

Also disagree. For years manufacturers have used same sized blocks for a wide range of displacements.
273-318-340-360
350-361-383-400
413-426-440

Either way, it seems that about 99% of 6.4L owners will ever even go into this limp mode unless they are really pushing the engine for a long period of time which most never will be in the right situation to do so.

Exactly.

I'm not sure where the topic got turned to oil temps, but 240-250-260 is not unheard of. Even among the turbo diesels with huge blocks and 2x the oil capacity. Them temps seen in the turbo are likely even higher.

I imagine with the added piston cooling oil jets and such the 6.4 probably does run warmer than the 5.7. Ram addressed this by improving the cooling and spec'ing a high quality synthetic oil that can operate safely at higher temps.

 

[Danno]

Drittal, no "Here ya go... and it goes back a few posts. Basically he thinks the 6.4 had the same performance on the Davis as the Ike because similar grade."

I feel that the 6.4 under it's max capacity should have performed better than the 6.0 at its max capacity. Also either other manufactures (ford and chevy) are severely underrating the capability and performance of their vehicles or one (ram) has asked theirs to do more than its capable of hints the gear hold feature.

You have experience with this feature correct??

 

[SouthTexan]

Here ya go... and it goes back a few posts. Basically he thinks the 6.4 had the same performance on the Davis as the Ike because similar grade.

Now back to you...

I didn't read anywhere in there where he stated that inclines approaching 6-7% grade will trigger the 6.4L limp mode. It looks to me that he was talking
the J2807 standard and how manufacturers do not have to specifically use Davis Dam just as long as it whatever they use meets certain requirements that are similar to Davis Dam.

I disagree, I think it is a number of factors, not just temp. I think it's more about sensing shifts from 1-2 and 2-1, WOT and high RPM over a certain time period.

Why? When I experiences the gear hold I was having no problem slowing down for 25mph hair pins then accelerating out of them at ~93% of my GCWR. T........

I would have to disagree with you as well. If you look at the 6.4L Ike Gauntlet videos, specifically the second one where they keep a camera on the gauge cluster, you will see that it was not constantly shifting between first and second gear. In fact it stayed in second for a long time and only down shifted to first gear once (and stayed there) before the limp mode kicked in.

Also disagree. For years manufacturers have used same sized blocks for a wide range of displacements.
273-318-340-360
350-361-383-400
413-426-440

Only the modern 5.7L(345ci), 6.2L(376ci), and 6.4L(392ci) share the same basic block and dimensions.

I'm not sure where the topic got turned to oil temps, but 240-250-260 is not unheard of. Even among the turbo diesels with huge blocks and 2x the oil capacity. Them temps seen in the turbo are likely even higher.

I imagine with the added piston cooling oil jets and such the 6.4 probably does run warmer than the 5.7. Ram addressed this by improving the cooling and spec'ing a high quality synthetic oil that can operate safely at higher temps.

No, diesels generally do not run into the 250F and up range. If it does then that would be very rare. I never even seen oil temps past 220F when towing and they usually stay between 201-203F when not towing. My Ecoboost 3.5L ran a little hotter between 201-210F when not towing and the highest I seen pulling a 10k trailer in the Texas +105F heat was upper 230Fs. I never seen it past 240F even when pulling 10K up and over the Rockies twice.

I have stated before that the reason why Ram requires a special oil is probably due to the higher than most engine oil temps it runs at. I am not saying it will ruin the engine, but I do think hotter temps are the reason why the truck goes into limp mode in certain conditions. Most have nothing to worry about, besides the inconvenience, since the ECM is doing it all to protect itself.

 

[drittal]

It couldn't perform to HP/TQ specs on IKE because of programming.

Thinking the gear hold programming is for anything other than what RAM has stated it was designed for, like oil or trans temps, is pure speculation.

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[SouthTexan]

It couldn't perform to HP/TQ specs on IKE because of programming.

Thinking the gear hold programming is for anything other than what RAM has stated it was designed for, like oil or trans temps, is pure speculation.

Well it is kind of hard to say the limp mode kicks in due to constant gear shifts when both videos clearly show that the truck did not shift gears more than once and that was to shift from 2nd to 1st as it was slowing down. I don't know about you, but I don't count one gear shift as being excessive.

Then there is also the fact that if it were due to transmission shifting then why hasn't anyone reported it in the 5.7L since it uses the same 66RFE? One would think that the transmission would need to shift more often with the 5.7L since it has less torque so by your theory the limp would occur more often with the 5.7L yet I have never heard of it happening with that engine. This is what leads me to believe it has more to do with the engine temps rather than the transmission temps.

 

[Danno]

It couldn't perform to HP/TQ specs on IKE because of programming.

Thinking the gear hold programming is for anything other than what RAM has stated it was designed for, like oil or trans temps, is pure speculation.

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How do you know it couldn't perform to HP/TQ specs on the IKE. It appears like it couldn't perform to the rated capacity from manufacture as we have seen the other can. Lose some weight and I beat it performs better.

Maybe if ram would provide a dyno of the 6.4 we could see the power curve.

Where did ram it was for oil and trans temp??

 

[drittal]

How do you know it couldn't perform to HP/TQ specs on the IKE. It appears like it couldn't perform to the rated capacity from manufacture as we have seen the other can. Lose some weight and I beat it performs better.

Maybe if ram would provide a dyno of the 6.4 we could see the power curve.

Where did ram it was for oil and trans temp??

1) because Ram said they programes it to perform in that manner in certain conditions for economy, driver comfort, and longer powertrain life.

2) ram didnt. It was speculated by South Texan that a temp reading was likely triggering gear hold.

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[SouthTexan]

2) ram didnt. It was speculated by South Texan that a temp reading was likely triggering gear hold.

If it is constant transmissions gear shifting that is triggering the limp mode like you say then tell me why did the truck go into limp mode on both Ike videos even though it only shifted once both times? Also, why hasn't there been any reports of 2500 5.7L owners having this very same issue since they use the very same transmission?

If your theory holds true, then you should be able to easily answer those questions.

 

[Danno]

1) because Ram said they programes it to perform in that manner in certain conditions for economy, driver comfort, and longer powertrain life.

2) ram didnt. It was speculated by South Texan that a temp reading was likely triggering gear hold.

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Driver comfort?? Are you saying they want the driver to have a white knuckle experience traveling 30mph on the interstate.

 

[U&A]

Driver comfort?? Are you saying they want the driver to have a white knuckle experience traveling 30mph on the interstate.

that would scar the hell out of me regardless of the circumstances.

disclaimer. this is not directed to, at form in out side by side, left right, anyone in this thread.

 

[drittal]

Driver comfort?? Are you saying they want the driver to have a white knuckle experience traveling 30mph on the interstate.

I'm saying Ram's explanation for implementing the gear hold program was for the reasons stated. I have posted this already, but if you choose you can rwad their explaination here...

http://www.tfltruck.com/2014/10/2014-ram-2500-hd-6-4l-hemi-and-gear-hold-feature-ike-gauntlet-video/

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[Iron Outlaw]

So with all these theories floating around about 6.4 engine Temps and the limp mode, could we just slap in a big ass radiator, lower temp thermostat and big oil cooler and avoid these high Temps and limp mode? I know my 6.4 runs at around 215 normally (empty) and that's high too me, but from reading around is "normal temp" for them. My old small block Chevys ran at 160-180. When it hit 210-220 I would start getting worried.

 

[SilverSurfer15]

1) times have changed. trans temps, oil change intervals, etc

2) its the thermostat... change to a 180 or 190

 

[Danno]

I'm saying Ram's explanation for implementing the gear hold program was for the reasons stated. I have posted this already, but if you choose you can rwad their explaination here...

2014 Ram 2500 HD 6.4L HEMI and Gear Hold Feature [Ike Gauntlet Video] - The Fast Lane Truck

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poor horse

Boy that 6.0 will run.

 

[drittal]

So with all these theories floating around about 6.4 engine Temps and the limp mode, could we just slap in a big ass radiator, lower temp thermostat and big oil cooler and avoid these high Temps and limp mode? I know my 6.4 runs at around 215 normally (empty) and that's high too me, but from reading around is "normal temp" for them. My old small block Chevys ran at 160-180. When it hit 210-220 I would start getting worried.

We have no idea if oil/trans temp is the trigger. Saying it so is just speculation.

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[drittal]

poor horse

Boy that 6.0 will run.

Then buy one and move on.

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[Dmopar74]

poor horse

Boy that 6.0 will run.

I own both a 6.0 Chevrolet with 4.10s and a 6.4 with 3.73s, the mopar will out perform the Chevrolet with more weight any day or the week. Is the 6.0 a good engine? He'll yeah but sometimes Internet commandos need to tuck their tail and run. Why don't you just go to a chev forum and talk **** about the 6.4, I'm sure you will become a Internet God in no time.

 

[SouthTexan]

We have no idea if oil/trans temp is the trigger. Saying it so is just speculation.

Then what triggers it? If you are about say excessive gear hunting just because that what was reported by TFL then answer these two questions.

1)Why did the 6.4L in both Ike videos trigger the limp mode even though it only shifted once?

2) Why hasn't this happened to the 5.7L trucks since they use the same 66RFE transmission?

These question should be easy to answer if your theory holds true. Although I do think it is funny that you have made comments against TFL basically saying they don't know what they are doing. Yet you will hold on to their words as if it is the Bible when it coincides with what you want to be true even though it defies logic.

 

[drittal]

South Texan, I watched the 2nd Ike again. You are correct, it pretty much shifts from 2nd to 1st once at 5:04 mark. Immediately the rpms rise and the truck starts to pick up speed and holds 5500 for a bit then smoothly the rpms fall to 4200 and it maintains that. When they were working it before they commented and laughed about 1mpg instantaneous at around 4000-4500 rpm in 2nd. When the Ram settles in at 4200 in 1st they comment about the 3mpg instantaneous.

To me, the gear hold program isn't temp related. They are 3 minutes and change into the run. As I stated before, mine kicked in before any temps were near the red. There are no warning lights or chimes. It isn't de-fueling until the the temps come down either. It is a threshold where through the programming it can tell if the truck can shift into 2nd and hold or accelerate. If the conditions aren't met and the program doesn't think it can hold 2nd it holds the engine at 4200 rpm until it can.

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