Do you see any repercussions to permanently turning off the mds?

[MrDazana]

The cam failure is not caused by the MDS system, its caused by the lack of oil pressure being pumped to the top of the engine when the engine is running idle. Some hemi ticks are caused by the MDS solenoid not being strong enough to engage/disengage it, usually starts happening after 120 000km.

My theory for disabling the MDS is to save the crack exhaust bolts. My theory behind this is when the engine is running on 4 cyl, there is a heat expansion difference on the block. Constant expansion retraction must not be good for aluminium blocks and thus we see a lot of people having cracked bolts and causing another type of hemi tick. Its always the same bolts that break, the ones near the cyl that get deactivated. I've never seen the ones in the middle break. I've had mine disabled since 8000k, now at 105000k, and still running original bolts.

 

[Joe Merchak]

Over the weekend I watched this guy claiming he is a FCA tech working over 10 year at 2 different FCA dealerships. Per him, all the failures he worken on the 5.7 were fleet vehicles due to excessive idling. He also said there were far more failures on the 6.4 then 5.7 but again these were fleet vehicles that had excessive idle hours. My friend works at a local FCA dealership and they see similar results. The only non-fleet vehicles they have seen were ones that did not change the oil at 5K miles. MY dealer recommends not to use the oil reminder but do the oil every 5K or 6 months.

 

[ToTheDarkSide]

Say if your trucks duty is to work non stop. Tow/haul mode 24/7. MDS never activates. You are running high RPMs. Oil pressure is right where it needs to be. The truck is meant to be operated like this right? Or they wouldn’t of given us the tow/haul button. Or they wouldn’t allow the tow/haul button to deactivate the MDS.
Where i drive, the hills never allow MDS to turn on anyways. The highways are rollercoasters so MDS will come on maybe twice in 20 miles.
So I say like many others have said, turn it off if you like. Change your oil at 5k with some good oil.
I think we have become complacent and have become dependent on computers and nonsense to tell us “do it when” instead of common sense telling us “do it now”.

 

[TomB 1269]

I am no mechanic or engineer, but I do research things heavily, I am good at grasping technical concepts and putting things together. I also understand engines well and have been working on my own cars for decades.

Cam / lifter failure from what I have read an pieced together seems to be very heavily related to excessive idling. My theory is that it has to do in part to how the lifters are oiled, and the fact that they are rollers vs flat tappet, as well as the fact that engines naturally get hot spots particularly when idling.

1st - My understanding is the lifters are oiled from top down thru the push rods.
2nd - Roller rockers do not spin in the bore during operation as do flat tappets.

With that being said, at Idle:
- oil pressure is low
- the amount of oil getting to the lifter is reduced
- engine gets hotter as coolant flow and air flow around the engine are reduced

Results:
- lifters get hot, and limited oil scorches on lifter sidewalls causing build up
- Build up increase resistance on lifter movement
- Resisted movement allows for lifter to loose contact with cam lobe
- Loss of contact between cam lobe and lifter results in high pressure impact once lobe and lifter make contact again
- Impact damage over time results in needle bearing failure and more "skidding" on cam lobe verse rolling
- Needle bearings finally fail and fall out and the roller position slides up in the lifter where the "arms" that support the roller shaft make contact with cam

So early stage failure shows signs of lifter roller "skidding" on cam lobe.
Late stage failure, i.e. engine misfire, etc. cam is gouged out.

Lastly, I can advise there is a fine line for idling. If you do not get the oil temp above 110 - 120 F then you will tend to have dry lifter tap upon start up the next morning. This is due in theory to the fact that cold oil does not activate its viscosity modifiers, therefore staying thinner i.e. 5 weight vs heavier at 20 weight when oil is at temp and drains easier & quicker from lifter. As well as the fact that the lifter is the last to get oil up on start up due to the top down oiling design in which oil to the lifters come thru push rod.

 

[HEMIMANN]

The cam failure is not caused by the MDS system, its caused by the lack of oil pressure being pumped to the top of the engine when the engine is running idle. Some hemi ticks are caused by the MDS solenoid not being strong enough to engage/disengage it, usually starts happening after 120 000km.

My theory for disabling the MDS is to save the crack exhaust bolts. My theory behind this is when the engine is running on 4 cyl, there is a heat expansion difference on the block. Constant expansion retraction must not be good for aluminium blocks and thus we see a lot of people having cracked bolts and causing another type of hemi tick. Its always the same bolts that break, the ones near the cyl that get deactivated. I've never seen the ones in the middle break. I've had mine disabled since 8000k, now at 105000k, and still running original bolts.

You'd think FCA would recommend 0W-20 for the 5.7 Hemi for this reason instead of 5W-20. Especially because weather varies so greatly across North America. Notably, FCA recommends 0W-40 for 6.4 Hemi. Way too wide a viscosity range for quality lubrication, to my knowledge. I'm going 0W-30 in winter and 5W-40 in summer. My truck engine ain't no Hellcat - though now they are with the TRX!

 

[46RamMan]

Don't be affraid to turn off MDS fellas. I know we like to think and ponder with stuff and there are horror stories all over the place pretty much about everything.. if your lifters are about to fail it doesnt matter if MDS is in or off, it doesn't matter you added mistery fluid and magical snake pee to your oil, it won't matter what color of oil you have. So Try to enjoy your stuff as much as you can and stay away from the horror story threads. You will find a more enjoyable experience with your Hemi, knocking on wood.

Sure some engines were built on Friday evening and the dude working on it wanted to rush things out and go home,but i'm sure a lot more were built on Monday when everybody was fresh and peachy.

As a data point,my idle speed is stock. 560-570rpm rigth now idling hot. ECT 203F, IAT 122F, engine oil pressure 43psi. Goes to 49 if I set my idle at 750rpm. Castrol Synth 5w30 with the Mopar oil filter.

Monday when everybody was fresh and peachy. or hung over from the all weekend parties....

 

[Harley Harrold]

Turned off the MDS on my truck at 73K miles in 2016 using my SuperChips CORTEX tuner. I switched engine oil from AMSOIL 5W20XL to AMSOIL 5W30XL at 85K miles, now have 92K miles with no problems. Oil pressure has remained the same @ idle
700 RPM: 35 PSI and 1,500 RPM: 55 PSI.

 

[chrisbh17]

Say if your trucks duty is to work non stop. Tow/haul mode 24/7. MDS never activates. You are running high RPMs. Oil pressure is right where it needs to be. The truck is meant to be operated like this right? Or they wouldn’t of given us the tow/haul button. Or they wouldn’t allow the tow/haul button to deactivate the MDS.
Where i drive, the hills never allow MDS to turn on anyways. The highways are rollercoasters so MDS will come on maybe twice in 20 miles.
So I say like many others have said, turn it off if you like. Change your oil at 5k with some good oil.
I think we have become complacent and have become dependent on computers and nonsense to tell us “do it when” instead of common sense telling us “do it now”.

Tow/Haul does NOT deactivate MDS, BTW.

Yes the Eco light does not come on the dash, but IIRC the only way to disable MDS is the Gear +/-.

 

[ramffml]

Tow/Haul does NOT deactivate MDS, BTW.

Yes the Eco light does not come on the dash, but IIRC the only way to disable MDS is the Gear +/-.

Yes it absolute DOES deactive MDS. I've tested this 20 times in a row. Going down an empty rural road, about 60 km/h, hold stead, MDS activates. Hit TH mode, MDS deactives. Hold steady for 30 seconds, turn off TH and MDS immediately activates.

You can try this a million times in your own truck, but on mine I've never had a single case where turning on TH mode has not turned it off.


Anyway, to the main point; while towing a trailer you won't ever enter MDS anyway, regardless of TH mode, because there is too much load on the engine. However, while towing, usually RPMs are going to be higher or 2000+ anyway, so maybe the higher RPM's would be how FCA intends the lifters/engine is getting oiled properly while towing with MDS disabled/off.

Lots of theorys, but I'm happy to hear the reports from guys with high mileage and disabled MDS, gives me peace of mind.

 

[Zoe Saldana]

Yes it absolute DOES deactive MDS. I've tested this 20 times in a row. Going down an empty rural road, about 60 km/h, hold stead, MDS activates. Hit TH mode, MDS deactives. Hold steady for 30 seconds, turn off TH and MDS immediately activates.

You can try this a million times in your own truck, but on mine I've never had a single case where turning on TH mode has not turned it off.


Anyway, to the main point; while towing a trailer you won't ever enter MDS anyway, regardless of TH mode, because there is too much load on the engine. However, while towing, usually RPMs are going to be higher or 2000+ anyway, so maybe the higher RPM's would be how FCA intends the lifters/engine is getting oiled properly while towing with MDS disabled/off.

Lots of theorys, but I'm happy to hear the reports from guys with high mileage and disabled MDS, gives me peace of mind.

If you want to try an experiment; you could add Lucas Synthetic Oil stabilizer to see if that stops the engine going into MDS under normal operation.

I asked Lucas if I could use it my truck and they said not if you have MDS

https://lucasoil.com/products/engine-oil-additives/pure-synthetic-oil-stabilizer

 

[ToTheDarkSide]

Tow/Haul does NOT deactivate MDS, BTW.

Yes the Eco light does not come on the dash, but IIRC the only way to disable MDS is the Gear +/-.

My 6.4 does

 

[ramffml]

If you want to try an experiment; you could add Lucas Synthetic Oil stabilizer to see if that stops the engine going into MDS under normal operation.

I asked Lucas if I could use it my truck and they said not if you have MDS

https://lucasoil.com/products/engine-oil-additives/pure-synthetic-oil-stabilizer

That sounds like a really terrible experiment

 

[BadHemi2014]

I just wanted to add an observation about oil pressure. My 5.7's warm idle oil pressure is around 48psi at stock idle.
I use the RP 20-820 filter and Redline 5W30.

I would like to suggest trying different oil filters to see if that raises your oil pressure. I know my oil pressure is higher with the RP filter than with the Fram Ultra (the good synthetic one, not the cheapie) I always used.

I should add, I always turn off MDS with the +/- and plan to continue, because I just don't like it!

 

[HEMIMANN]

I just wanted to add an observation about oil pressure. My 5.7's warm idle oil pressure is around 48psi at stock idle.
I use the RP 20-820 filter and Redline 5W30.

I would like to suggest trying different oil filters to see if that raises your oil pressure. I know my oil pressure is higher with the RP filter than with the Fram Ultra (the good synthetic one, not the cheapie) I always used.

I should add, I always turn off MDS with the +/- and plan to continue, because I just don't like it!

Yeah, Red Line's polyol ester formula has a lot stiffer VI than all the other Group III & IV hydrocarbon chain oils. I'm thinking 0W-30 winter & 5W-30 summer. Before I switch, I'm running FCA's recommended PUP 0W-40 in my 6.4 Hemi.

Today it was 23 degrees for a high temp when driving around. With oil warmed up fully, idle oil pressure was 33 psi, highway oil pressure was 55 psi. Oil temp was only 193F due to cold weather. Usually up around 215F on warm days.

What was the difference in oil pressure between Royal Purple & Fram Ultra Filters? If it's significant, I might stick with Fram Ultra. Otherwise RP will go into bypass more often. Maybe that's ok?

 

[BadHemi2014]

What was the difference in oil pressure between Royal Purple & Fram Ultra Filters?

I wish I had a pic to give an exact#, but I know it was in the mid to high 30s, definitely not over 40, with the Fram, and similar #s with another filter which one escapes me at the moment. But now with the RP it is always 47-48 psi at warm idle.

Of course that's just my truck it seems like each of these hemis has its own set of requirements!

 

[Joe Merchak]

Yes it absolute DOES deactive MDS. I've tested this 20 times in a row. Going down an empty rural road, about 60 km/h, hold stead, MDS activates. Hit TH mode, MDS deactives. Hold steady for 30 seconds, turn off TH and MDS immediately activates.

You can try this a million times in your own truck, but on mine I've never had a single case where turning on TH mode has not turned it off.


Anyway, to the main point; while towing a trailer you won't ever enter MDS anyway, regardless of TH mode, because there is too much load on the engine. However, while towing, usually RPMs are going to be higher or 2000+ anyway, so maybe the higher RPM's would be how FCA intends the lifters/engine is getting oiled properly while towing with MDS disabled/off.

Lots of theorys, but I'm happy to hear the reports from guys with high mileage and disabled MDS, gives me peace of mind.

I pull a trailer alot, so I use Tow/Haul alot. Eco and MDS does engage in tow haul. When on flat road and trans is in 8th and not calling for much power the engine will go into eco and MDS. I usually tow with the trans set to manual in gear 8, but I have had times were I stopped and forgot to put it back in manual mode and it will switch, then I get the reminder from the wife as she can even tell it switch to 4 cyl mode. I dont think yours is a good test since you are switching mid cycle. Start out in tow/haul and try it.

My truck is a 2018 express, hemi, 8 speed, 3.21 gear in case that matters.

 

[chrisbh17]

I pull a trailer alot, so I use Tow/Haul alot. Eco and MDS does engage in tow haul. When on flat road and trans is in 8th and not calling for much power the engine will go into eco and MDS. I usually tow with the trans set to manual in gear 8, but I have had times were I stopped and forgot to put it back in manual mode and it will switch, then I get the reminder from the wife as she can even tell it switch to 4 cyl mode. I dont think yours is a good test since you are switching mid cycle. Start out in tow/haul and try it.

My truck is a 2018 express, hemi, 8 speed, 3.21 gear in case that matters.

Reading around it seems either hit or miss (some trucks do, some trucks dont use MDS in tow/haul) or its hard to tell if its MDS engaging or the torque converter locking up. Im guessing its the latter, I cant see Chrysler having unique programming for certain trucks.

The 8 speed trans can have partial or full lockup in any gear, so its possible we're feeling that OR MDS OR both. I was looking through AlfaOBD last night to see if there is a data point that can be monitored to tell if MDS is engaged, but I could not find one.

Tow/Haul supposedly changes the shift points, so when you press it while driving it will most likely "buck/boost" the gear you are in. That feeling isnt MDS engaging/disengaging.

 

[Joe Merchak]

Reading around it seems either hit or miss (some trucks do, some trucks dont use MDS in tow/haul) or its hard to tell if its MDS engaging or the torque converter locking up. Im guessing its the latter, I cant see Chrysler having unique programming for certain trucks.

The 8 speed trans can have partial or full lockup in any gear, so its possible we're feeling that OR MDS OR both. I was looking through AlfaOBD last night to see if there is a data point that can be monitored to tell if MDS is engaged, but I could not find one.

Tow/Haul supposedly changes the shift points, so when you press it while driving it will most likely "buck/boost" the gear you are in. That feeling isnt MDS engaging/disengaging.

You can here the engine is in 4cyl mode as the exhaust note changes. That would not happen with a torque converter lockup.

 

[ramffml]

I pull a trailer alot, so I use Tow/Haul alot. Eco and MDS does engage in tow haul. When on flat road and trans is in 8th and not calling for much power the engine will go into eco and MDS. I usually tow with the trans set to manual in gear 8, but I have had times were I stopped and forgot to put it back in manual mode and it will switch, then I get the reminder from the wife as she can even tell it switch to 4 cyl mode. I dont think yours is a good test since you are switching mid cycle. Start out in tow/haul and try it.

My truck is a 2018 express, hemi, 8 speed, 3.21 gear in case that matters.

My truck won't even enter 8th gear when pulling my trailer, there is no way it's going into MDS since even unloaded, anything other than a flat road with no wind will cause MDS to deactivate. Like I said, when empty I play piano on the TH switch and the ECO light will flicker in and out, 20 times in a row, along with the corresponding jerk + exhaust note. I won't argue that the 4th gens might be different, but that's probably where the confusion lies because at one time ECO light just meant "driving economically" but as of 2019/5th gens it's definitely tied to MDS.

 

[RedSRT4Me]

My 2015 had MDS turned off at 28,000 near the end of 2016. She has 107,000 now and runs like a ***** ape.