Living with MDS, 2019 6.4 w/ 65k

Docwagon1776 · Jan 11, 2023

DA Smith said:
After driving all the Rams I've had and usually putting 100k on them before getting another one adds up to about 900,000 k miles. Never had any mechanical issues so I guess when you drive a Ram you really don't have to be too sensitive or in tune with your Truck because they just keep on going. I think the problem with these people saying how they feel the MDF is mainly a mental issue because they don't like the thought of running on four cylinders when eight is not needed.

Human perception is funny, hence placebos in studies and the fact telling someone to not think about elephants makes them immediately think about elephants. Also why stickers add at least 5 hp each.

Some years ago I hit a snow plow caster that had fallen off a plow with my Charger. This, predictably, damaged the subframe. I was back in a Crown Vic for a bit. I found myself routinely driving 10-15mph slower because the Crown Vic was just so much more visercal in feedback. Clapped out suspension meant more motion, more wind noise and less cabin insulation meant more auditory feedback, etc. The CVPI *felt* faster at the same speed than the Charger due that feedback, despite objective reality differing from my perceptions. So, while I don't doubt people's perceptions I do doubt their version of reality without objective proof. Except stickers. Common knowledge those work.

tron67j · Jan 11, 2023

I know the difference in between MDS engaged and with it off. There is a feeling of sluggishness as I regularly drive a level 2-mile long road if I don't adjust with tow mode button. I also feel it other times, but honestly it doesn't bother me. There is a miles-long thread in 4th gen on this. Consensus there is that the MDS engaging and Eco light have no direct correlation and it makes trucks with performance mufflers sound horrible.

Docwagon1776 · Jan 11, 2023

ramffml said:
Oil viscosity doesn't change it noticeably, in fact there is more viscosity change going from -20 deg C to 100 deg C (like my truck does in the winter) vs going from a 20w to a 30w at 100 deg C.

Sure, which is why the MDS system keeps track of your oil temperature (and won't activate when oil temps are outside a certain range). The computer can compensate for temp changes since it knows that, but obviously it doesn't know what oil you put in and relies on it meeting the requirements.

ramffml · Jan 11, 2023

Docwagon1776 said:
Sure, which is why the MDS system keeps track of your oil temperature (and won't activate when oil temps are outside a certain range). The computer can compensate for temp changes since it knows that, but obviously it doesn't know what oil you put in and relies on it meeting the requirements.

My truck activates MDS when it's still cold. I've never noticed any difference in smoothness based on whatever temperature it's at. Only recently has it gotten better (and again I'm running a thicker oil in cold temps).

Docwagon1776 · Jan 11, 2023

ramffml said:
My truck activates MDS when it's still cold. I've never noticed any difference in smoothness based on whatever temperature it's at. Only recently has it gotten better (and again I'm running a thicker oil in cold temps).

Perhaps this is no longer current, but what I've seen is:

The PCM will activate the 4-cylinder mode when the following enabling conditions are met:

Low engine load

1200 to 3000 rpm

Vehicle speed between 12 mph and 90 mph

Battery voltage from 9 volts to 15 volts

Oil pressure from 15 psi to 147 psi

Oil temperature greater than 120 F

Engine coolant temperature from 158 to 248 F

Ambient temperature from 14 F to 248 F

No throttle position sensor or MDS faults

ramffml · Jan 11, 2023

Docwagon1776 said:
Perhaps this is no longer current, but what I've seen is:

The PCM will activate the 4-cylinder mode when the following enabling conditions are met:

Low engine load

1200 to 3000 rpm

Vehicle speed between 12 mph and 90 mph

Battery voltage from 9 volts to 15 volts

Oil pressure from 15 psi to 147 psi

Oil temperature greater than 120 F

Engine coolant temperature from 158 to 248 F

Ambient temperature from 14 F to 248 F

No throttle position sensor or MDS faults

It activates far lower than 120 F. I can take a pic of my dash next time if I remember.

Docwagon1776 · Jan 12, 2023

ramffml said:
It activates far lower than 120 F. I can take a pic of my dash next time if I remember.

Don't have to prove it to me, I'll take your word. Like I said, that list may be outdated. The point remains the system knows the oil temp and can adjust for it.

ramffml · Jan 12, 2023

Docwagon1776 said:
Don't have to prove it to me, I'll take your word. Like I said, that list may be outdated. The point remains the system knows the oil temp and can adjust for it.

This is what you wrote:

Docwagon1776 said:
Of course the 6.4L is different, but using a thicker oil than called for likely would delay the pressure building back up and exacerbate it in colder temps.

My point was that the thicker viscosity of the oil that some of us are running isn't what is causing the MDS jerkyness. Because oil naturally gets thinner as it heats up and my truck (when it jerks) doesn't jerk worse or less depending on how hot is, and secondly because my truck (if anything) is jerkying less now with 0w-30 than it ever did running 0/5w-20.

Docwagon1776 · Jan 12, 2023

ramffml said:
This is what you wrote:

Right...not simply because the oil is thicker but because it won't be the thickness the computer thinks it is based on temperature. If the computer is adjusting based on temperature, which it is, it's doing so based on a formula that assumes a certain weight of oil is in the motor.

And if a thicker oil works better, awesome for those who have all the maladies.

ramffml · Jan 12, 2023

Docwagon1776 said:
Right...not simply because the oil is thicker but because it won't be the thickness the computer thinks it is based on temperature. If the computer is adjusting based on temperature, which it is, it's doing so based on a formula that assumes a certain weight of oil is in the motor.

And if a thicker oil works better, awesome for those who have all the maladies.

I'm not sure what part you're not getting; there has been no difference in jerkyness regardless of temp or oil viscosity in my truck. Viscosity has nothing to do with how jerky it can be in some trucks.

Docwagon1776 · Jan 12, 2023

ramffml said:
I'm not sure what part you're not getting; there has been no difference in jerkyness regardless of temp or oil viscosity in my truck. Viscosity has nothing to do with how jerky it can be in some trucks.

ramffml said:
and secondly because my truck (if anything) is jerkying less now with 0w-30 than it ever did running 0/5w-20.

Which one am I supposed to reply to? No difference or (if anything) less jerky? Again, perception that even you can't quite quantify.

Docwagon1776 said:
And if a thicker oil works better, awesome for those who have all the maladies.

Do you need to argue so badly that even once I say great if it works for you need to recant to keep it going? Damn. You can have the last word.

ramffml · Jan 12, 2023

Docwagon1776 said:
Which one am I supposed to reply to? No difference or (if anything) less jerky? Again, perception that even you can't quite quantify.

Do you need to argue so badly that even once I say great if it works for you need to recant to keep it going? Damn. You can have the last word.

Actually I'm just replying because I have no idea what you're trying to argue half the time. As of your second last post it seems to me you're still implying that "out of spec" oil can be causing the MDS to work worse than the "real" oil. If you're no longer suggesting that, great, no more arguments from me and I just read your post wrong.

Bandit1859 · Jan 12, 2023

DerickE said:
Hi all, I've been thinking about, testing, and playing around with MDS on my new-to-me 2500. I guess my question is simply this: what is the best way to manage MDS and live with it?

I've tried doing the gear limit thing to temporarily disable it. My fuel efficiency drops but its predictable and dont have the 'thunk' of MDS engaging and disengaging. The process works fine, but it's dumb and I really dont care to do it each and every drive. So, are we doing 3k oil changes....or using additives...or what? Obviously Durge designed an entire engine platform around it...so they felt it was something to buy into....I just want to know what the average joe can do to make sure the motor is in a reliable state while using the designed MDS system.

Really my 2019 you can’t hardly tell it is doing it. Maybe yours needs to be looked at. Not a big deal

Riccochet · Jan 13, 2023

I can 100% tell when MDS activates and deactivates. Then again I'm a gearhead that's used to hearing/feeling changes in engine function.

I almost always manually set to gear 8 or use tow/haul. The change in fuel economy is nearly zero without MDS. Some say that MDS causes premature lifter/cam failure. Whether that is true or not, who knows.

JerryETX · Jan 13, 2023

Bandit1859 said:
Really my 2019 you can’t hardly tell it is doing it. Maybe yours needs to be looked at. Not a big deal

From what I gather in reading hundreds of comments on MDS sounds like it's not nearly as loud or noticeable in the 5.7 as it is in the 6.4. And I think it's even worse on sub 2019's with the 6.4 and the 6 speed. I'd be shocked if one person out of a 100 drove my 2016 6.4 and didn't immediately notice when the MDS kicked in.

buckeyexx · Jan 13, 2023

JerryETX said:
From what I gather in reading hundreds of comments on MDS sounds like it's not nearly as loud or noticeable in the 5.7 as it is in the 6.4. And I think it's even worse on sub 2019's with the 6.4 and the 6 speed. I'd be shocked if one person out of a 100 drove my 2016 6.4 and didn't immediately notice when the MDS kicked in.

I‘m on my third ram with mds. My first was a 2011 1500 with the 5.7 and I could definitely tell when it kicked in but nearly as much as my 2015 2500 with the 6.4. Even before I installed the after market exhaust it was noticeable right away. With the aftermarket exhaust it was ridiculous. Now with my 2016 power wagon with the 6.4 and with stock exhaust I can honestly barely feel it. I know it’s there obviously because I’ve dealt with it in the past but I can run down the highway and forget that I didn’t disable it. I still disable it even though it’s not as noticeable just because it still has that lag I don’t like. When I eventually swap the exhaust on this one Im sure it will be much more noticeable. Not sure why it seems to behave better in the 2016 but it does for sure. To be honest the 6.4 in this truck it a lot quieter all the way around. The 2015 motor was a very noisy motor compared to the 2016.

AlexC2350 · Jan 14, 2023

JCE said:
FYI, my 2019 2500 6.4 doesn't "clunk" when MDS activates or deactivates and I'm just over 66k miles.

My 2020 does clunk when mds disengages. It comes on way too easily and stays on far too long. Even when gently accelerating up a hill. This is my third and hemi and second 6.4. The other ones acted much differently. My 5.7 1500 was seemless. My thought is that my ‘20 has 4.10s and this has something to do with it.

I deactivate MDS all the time unless I’m doing strictly highway, For the reasons above.

DerickE · Jan 17, 2023

Bandit1859 said:
Really my 2019 you can’t hardly tell it is doing it. Maybe yours needs to be looked at. Not a big deal

I dont think so at this point...as others have said it varies a bit, but perhaps youre just used to it. I notice it way more when I'm driving with my foot, than when on cruise control though. I barely notice it at all there. Also, because it was a new-to-me situation, I was probably also hyper sensitive to changes on a new vehicle while getting used to it. With the commentary of folks here, I chilled out about it, and stopped paying SO MUCH attention to it. lol.

Docwagon1776 · Jan 18, 2023

DerickE said:
I dont think so at this point...as others have said it varies a bit, but perhaps youre just used to it. I notice it way more when I'm driving with my foot, than when on cruise control though. I barely notice it at all there. Also, because it was a new-to-me situation, I was probably also hyper sensitive to changes on a new vehicle while getting used to it. With the commentary of folks here, I chilled out about it, and stopped paying SO MUCH attention to it. lol.

If I pay attention to it and consciously look for it, I can hear the slight change and feel the slight vibration and mostly through the pedal like you. I'm not a machine whisperer, or alternately have driven so many older trucks were noise and vibration were much more prevalent, that as I've said I don't notice it at all normally. I mean, I drove an '87 318/4M with 35" tires for a *long* time and it had a touch more of the shakes.

Living with MDS, 2019 6.4 w/ 65k

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