How do I know if my 5.7 has MDS

[Curmudgeon]

Confused me too (4th Gen here) so I checked it this morning.
Sure enough, with ECO showing in my EVIC, I could get the ECO indication to go "off" and then back "on" just by pressing the +/-buttons. No change to speed, accel, etc.

That said, at just 35mph I could feel the MDS running my 5.7 on 4 cylinders no matter what the light said. I consider MDS on my truck to be pretty smooth but I can pick up on it anytime I'm paying attention to it.

Either way, I am almost daily surprised by how much I learn just lurking and reading through, so thanks to all; those with questions and those with answers. Even correct v incorrect leads to interesting conversations.

Note to Self: proofread 1st, THEN click submit.
I just realized my quoted post is inconsistent and makes no logical sense.
So... sorry for my confusion.

 

[Racer9]

On my '18 GMC, if I put the shifter in manual or low, there is an indicator on the dash that reads V8 or V4. I toggle shift it to 5th and it never goes to V4.
On my '11 Ram with 5 speed I don't think there is such a thing, (I deleted via Diablo) but with the 6 speed auto you can. https://blog.1aauto.com/what-is-mds-how-do-i-disable-it-on-my-hemi-engine/

 

[Wild one]

When you're driving in-town in lower speeds, especially in traffic... when you feel the shudder and lag, and a general sense of WTF... that's MDS.

In my opinion, MDS does nothing to better fuel economy and is only a detriment to ones driving experience and transmission as it's hunting to find a happy engine rpm based on load.
I just can't stand MDS and see no need for it whatsoever.

I have excellent fuel economy (or as best as possible in my HEMI..lol) and always put my truck in 8 on the EVIC.

All 8 HEMI cylinders, All the time (my personal opinion only though).

Downside to that,is the lifters get less oil,so it's 6 of 1 and 1/2 dozen of the other type scenerio. When Ma Mopar deletes MDS,she also replaces the solenoids with plastic plugs that allow full oil flow to the lifters.When you defeat the mds via shifter or tune,the solenoids reduce the amount of oil reaching the lifters. Just something to think about.

 

[markabby]

had to drive a while today, so, i turned mine off via the gear selector on the steering wheel...man, what a difference!! The truck was more responsive and, believe it or not, i was getting 22.5 MPG on the highway.

I have to bring it in for an oil change soon, i'm going to ask if they can permanently disable it.

I was just told the dealer will not disable it...so, i'll just use the gear select buttons.

 

[markabby]

There's no mds solenoids or even the wiring for them,left in my 4th gen,and the eco light still comes on in it.
The hemi has had mds right from when it was introduced in 03,the engine was designed from word go with mds.
Some of the earlier HD trucks with the 5.7 were mds delete,but pretty well every other vehicle with an automatic transmission has mds.The exception being the 5.7 and 6.4 Challengers with the 6 speed manual transmission,they don't have mds.
The cams are differant from a MDS cam and a non-MDS cam,and of the course the MDS lifters are differant from a non-MDS lifter.When Ma Mopar deletes the MDS,she also replaces the MDS solenoids with plastic plugs that allows full oil flow to the lifters,as running a MDS engine,in non-MDS mode cuts oil flow to the lifters.If you're one of the guys who likes to defeat the MDS by running it with 8th showing on the EVIC,just be forewarned,you're cutting oil flow to the lifters,which isn't really a wise decision .
Every Hemi from 09 up has VVT / variable valve timing.
From 09 up all 5.7 and 6.4 trucks and 6.4 cars have had the variable intake manifold with a long runner intake for torque,and it switches over to a short runner intake roughly in the 4,000 to 4200 rpm range,the exception to that are the car 5.7's ,which don't have the dual runner intake,they just employ a long runner intake. They also employ a differant cam,from the truck 5.7's because of the intake manifold

just read a big dispute over this in another forum. Some guys believe this to be true, while others strongly disagree. (that lifters are not being oiled when mds is off) Some have said they turned theirs off from the start of owning their trucks and never had a problem. I haven't read anyone having lifter issues because mds was turned off. So, it seems its a theory right now.

I know there's a video on YT and the guy claims the lifters went bad because mds was turned off, but it was his theory, since hemis are/were notorious for lifter issues anyway.

So, if anyone here can honestly make a claim they had lifter issues went bad because mds was turned off, they should post it. I find it had to believe that the hemi was designed NOT to sufficiently oil lifters, because even when towing a heavy load, the mds isn't working...and that's a time when you want your engine oil flowing.

MDS was created to make a large engine, like a hemi, allegedly be more fuel efficient. I stated in a post that i turned mine off today for a 50 mile ride and i actually got better fuel economy and a more responsive truck, but, if you bought a truck with a hemi, fuel economy should not really be a major concern. As i was once told: "A hemi will pass anything on the highway, except for the next gas station"

 

[chopperman1]

The cams are differant from a MDS cam and a non-MDS cam,and of the course the MDS lifters are differant from a non-MDS lifter.When Ma Mopar deletes the MDS,she also replaces the MDS solenoids with plastic plugs that allows full oil flow to the lifters,as running a MDS engine,in non-MDS mode cuts oil flow to the lifters.If you're one of the guys who likes to defeat the MDS by running it with 8th showing on the EVIC,just be forewarned,you're cutting oil flow to the lifters,which isn't really a wise decision .

@Wild one, Do you have a source for "cutting flow to the lifters"? My understanding of it's function is that the solenoid opens the bleed port on the lifter which essentially stops the lifter from pumping up thus stoping in from actuating the valves. The oil supply to the lifter doesn't change.

Source:

1. Then the computer opens the MDS solenoid which supplies oil pressure to the lifter deactivation ports.
2. This oil pressure passes through the hole in the side of the lifter and decouples the inner plunger from the lifter body. This “deactivates” the lifter.
3. The deactivated lifters will not open the valves. However, enough pressure is left to keep the pushrods from rattling and the lifter following the cam.

What are HEMI Multi-Displacement System (MDS) Valves? How do they work?

Multi-Displacement System (MDS) valves deactivate 4 of the 8 lifters in a (V8) cylinder system when the throttle is closed or in cruise mode at low RPM. The purpose of this feature is to enhance the fuel economy available to the HEMI engines introduced by Chrysler. ALL Mopar models 2005+ are...

10secondracing.com

 

[markabby]

if you don't mind reading, found an extensive writing on MDS here:

What are HEMI Multi-Displacement System (MDS) Valves? How do they work?

Multi-Displacement System (MDS) valves deactivate 4 of the 8 lifters in a (V8) cylinder system when the throttle is closed or in cruise mode at low RPM. The purpose of this feature is to enhance the fuel economy available to the HEMI engines introduced by Chrysler. ALL Mopar models 2005+ are...

10secondracing.com

 

[Wild one]

@Wild one, Do you have a source for "cutting flow to the lifters"? My understanding of it's function is that the solenoid opens the bleed port on the lifter which essentially stops the lifter from pumping up thus stoping in from actuating the valves. The oil supply to the lifter doesn't change.

Source:

1. Then the computer opens the MDS solenoid which supplies oil pressure to the lifter deactivation ports.
2. This oil pressure passes through the hole in the side of the lifter and decouples the inner plunger from the lifter body. This “deactivates” the lifter.
3. The deactivated lifters will not open the valves. However, enough pressure is left to keep the pushrods from rattling and the lifter following the cam.

What are HEMI Multi-Displacement System (MDS) Valves? How do they work?

Multi-Displacement System (MDS) valves deactivate 4 of the 8 lifters in a (V8) cylinder system when the throttle is closed or in cruise mode at low RPM. The purpose of this feature is to enhance the fuel economy available to the HEMI engines introduced by Chrysler. ALL Mopar models 2005+ are...

10secondracing.com

The solenoids aren't anywhere near the lifters,and aren't close enough to the lifters to activate any part of the lifter,the solenoids provide more oil flow to push the pins in,to release the lifter body from the lifter plunger




This is right from your article,as you can see the solenoids open and provide more oil to the lifters to deactivate or push the pins in on the side of the lifter body,which lets the MDS lifters collapse .To activate MDS mode,the solenoids have to provide more oil to the lifter gallery.

1. The computer shuts off fuel to the MDS controlled cylinder.
2. Then the computer opens the MDS solenoid which supplies oil pressure to the lifter deactivation ports.
3. This oil pressure passes through the hole in the side of the lifter and decouples the inner plunger from the lifter body. This “deactivates” the lifter.
4. The deactivated lifters will not open the valves. However, enough pressure is left to keep the pushrods from rattling and the lifter following the cam.
5. Since no air can get in or out, the engine is running on the remaining four cylinders. The deactivated cylinders act like air springs. This keeps the engine running smoothly and minimizes pumping loss.

From farther down the article.

Cutaway version of a Hemi MDS lifter. The key thing here is the transverse pin exposed to oil pressure from the orifice in the lifter body. As the fluid circuit energizes, the pin is pushed in, unlocking the plunger inner body from the lifter's outer body. In this manner, the roller tip can follow the cam lobe without the plunger moving the pushrod up and down.

The lifter valley of a stock 5.7L Hemi without MDS. Notice the two white plugs next to the cam tunnel? These are where the MDS solenoids would normally go. Truck engines like this one were not equipped with MDS, and had these plugs instead.
Photo by Douglas Glad.

This is the MDS solenoid that plugs into the lifter valley in four holes adjacent to the cam tunnel. These go where the blank plugs were shown in an earlier photo of the lifter valley.
Photo by Dave Young.

At first glance, this replacement Dorman MDS lifter transducer looks like an injector, as many of its parts act similar to an injector's. These often get clogged with particles from the oil. When that happens, the lifters can fail if the solenoid is not replaced.
Getting cylinder deactivation to happen from a practical standpoint takes some pretty precise engineering. Within the lube circuit of the Hemi's hydraulic roller lifters are four control valve solenoids that when energized by the ECM through the harness divert pressurized oil to a locking pin in the lifter. When this pin is pushed into the body of the lifter, the roller on the lifter can still follow the cam profile, but the motion is no longer translated to the plunger—the part of the lifter that engages the pushrod. When the ECM de-energizes the solenoid, the spring-loaded pin engages with the plunger and all the parts of the lifter have the same motion again.
A few things can happen that can cause this mechanism to break down, the most common of which is oil contamination. When small pieces of dirt block the lube circuit, the lifter may not be able to change state, or the change may happen slower, or only partially. A common scenario with the MDS system in Hemis is where the ECM believes the lifter is engaged at higher rpm when it is not. Here, the internal pin that locks the lifter body to the plunger is still disengaged when the engine rpm goes up. In this failure mode, the roller follows the cam lobe, until it reaches an engine speed where it can't, and the roller crashes repeatedly on the lobe. Eventually, the lifter, roller, needle bearings, and the lobe surface become damaged to the point of failure.


And then there's also this video,that goes into a good explanation of how the MDS system works,and the differance in the MDS block off plug,and the MDS solenoid. Towards the end of the video,he talks about the factory MDS block-off plugs.

Is MDS Damaging Your HEMI? The Answer May Surprise You!

I feel like MDS has been unfairly made the culprit for the lifter failures we see on Gen 3 Hemi engines. In this video I explain exactly how the system works...

www.youtube.com

 

[Wild one]

Uncle Tony also has a good video,that's worth watching if you haven't seen it. It shows the downfall of the redesigned 09 and later VVT block. It also shows why one of the best benefits to oiling the lifters is to up the idle rpm,and drive the engine in an aggressive manner,as the oil flung off the crank,is still where the the lifter roller and cam lobe receive the majority of their lubrication

A Closer Look At The Mopar Gen 3 Hemi And It's Often Fatal Flaw

Our first video concerning Mopar's Gen 3 Hemi's notorious camshaft and lifter failure phenomenon caused a lot of discussion and controversy. It has nothing ...

www.youtube.com

 

[diymirage]

Uncle Tony also has a good video,that's worth watching if you haven't seen it. It shows the downfall of the redesigned 09 and later VVT block. It also shows why one of the best benefits to oiling the lifters is to up the idle rpm,and drive the engine in an aggressive manner,as the oil flung off the crank,is still where the the lifter roller and cam lobe receive the majority of their lubrication

A Closer Look At The Mopar Gen 3 Hemi And It's Often Fatal Flaw

Our first video concerning Mopar's Gen 3 Hemi's notorious camshaft and lifter failure phenomenon caused a lot of discussion and controversy. It has nothing ...

www.youtube.com

not sure if id trust tony on much of anything

 

[Wild one]

not sure if id trust tony on much of anything

Really not much to distrust on this video,on some things i'll admit you have to take him with a grain of salt,but in this video,he's pretty well just pointing out the obvious. Tom Hoover is the famous engineer that was consulted on the vvt,the man was a veritable genius in some respects,but i think he seriously flucked up by putting the vvt tunnel where he did.They had to redesign the block anyways,so why they didn't locate the vvt oil passage above the cam i don't know.If the oil passage was above the cam,that would of allowed them to keep the cam in the same position as the earlier blocks,and they could of re-engineered the lifters to be closer to vertical,so they'd at least have a little more benefit from the oil leaking past the lifter body. But those are only my thoughts,and i'm not the sharpest cookie in the bag

 

[04fxdwgi]

As I mentioned before, a set of piston squirters (like in the truck engines), mounted under the valley and fed from the oil galley would do the trick. They could be aimed directly at the individual lifters where they exit the bore, and would ensure the exposed lifter body and roller were lubricated, with pressurized oil, not just splash.

 

[CanuckRam1313]

I don't disagree that there is merit to these published articles.

From my personal experience, I have used my gear selector and put it in 8 since day one, almost 5-years and almost 160,000Km's ago.

Not one issue, and only a happier HEMI with no lag issues and stumbling transmission.

 

[markabby]

I don't disagree that there is merit to these published articles.

From my personal experience, I have used my gear selector and put it in 8 since day one, almost 5-years and almost 160,000Km's ago.

Not one issue, and only a happier HEMI with no lag issues and stumbling transmission.

i read in another article that they turn off the MDS in police highway vehicles to give them more response and speed. So, the state police vehicles have been doing that for years without any problems. In those police cars, the MDS is completely eliminated from the engine....i believe at the manufacturer.

 

[Wild one]

As I mentioned before, a set of piston squirters (like in the truck engines), mounted under the valley and fed from the oil galley would do the trick. They could be aimed directly at the individual lifters where they exit the bore, and would ensure the exposed lifter body and roller were lubricated, with pressurized oil, not just splash.

I've been saying the same thing for years to, the piston squirters should be aimed at the cam lobes instead of at the upper rod bearings and bottom of the pistons.

 

[Wild one]

i read in another article that they turn off the MDS in police highway vehicles to give them more response and speed. So, the state police vehicles have been doing that for years without any problems. In those police cars, the MDS is completely eliminated from the engine....i believe at the manufacturer.

I'm a firm believer in deleting MDS,but only if it's done properly. That entails swapping the cam / MDS lifters for non-MDS lifters,and swapping out the MDS solenoids for either Ma Mopars plastic block-off plugs or Stanke's billet aluminium plugs,and then increasing the idle rpm to at least 750 rpm. But i'm no fan of defeating MDS via a tune or using the gear limiter button , as that cuts oil flow to the lifter bores.

 

[mikeru]

Downside to that,is the lifters get less oil,so it's 6 of 1 and 1/2 dozen of the other type scenerio. When Ma Mopar deletes MDS,she also replaces the solenoids with plastic plugs that allow full oil flow to the lifters.When you defeat the mds via shifter or tune,the solenoids reduce the amount of oil reaching the lifters. Just something to think about.

I've heard this theory before. And at the time it made sense to me. I've also seen conflicting theories where someone was debunking it, saying that the oil that is cut off when MDS is disabled isn't used for lubrication. The MDS lifters are still being lubricated the same way as the non-MDS lifters. I can't say either way because I'm not intimately familiar with how the MDS lifters work. But I do know that on 5th gen 1500's, the tow/haul button disables MDS. I doubt they would design an engine in which four of the lifters received less lubrication when it's being used the hardest. Just my take on it.

 

[Wild one]

I've heard this theory before. And at the time it made sense to me. I've also seen conflicting theories where someone was debunking it, saying that the oil that is cut off when MDS is disabled isn't used for lubrication. The MDS lifters are still being lubricated the same way as the non-MDS lifters. I can't say either way because I'm not intimately familiar with how the MDS lifters work. But I do know that on 5th gen 1500's, the tow/haul button disables MDS. I doubt they would design an engine in which four of the lifters received less lubrication when it's being used the hardest. Just my take on it.

There is a "but" to that theory though,and that "but" is why does Ma Mopar change the solenoids out for block off plugs that allow full oil flow to the lifter bores on the factory non-MDS vehicles ,if they didn't think the lifter gallery needed more oil flow. Tony's video shows a lifter with scuffing/wear on the lifter body,and that only occurs because of lack of oil to the lifter bore. I actually think the trucks aren't really designed for towing as much as they're designed for the average driver who never tows or goes off road , that's their biggest market share , and is the one they worry about the most . The majority of drivers only look at the milege sticker when buying a new vehicle , and MDS allows them to post a higher milege number on the window sticker , i've never seen a window sticker list towing milege

 

[mikeru]

Who is this Ma Mopar and why is she deleting MDS? Actually, as I said I'm not familiar enough with the system to really argue either way. So any argument I'm providing is pretty much my way of thinking. I know plenty of people who never tow with their 1500 (myself included), but I also know lots of people who do tow their toys with them regularly. Lots of people here do the same. While it's true that truck makers don't include towing mileage, I don't see how they possibly could. There are too many variables involved to do that. They do give tow ratings, so how can that not influence vehicle (engine) design? In the end, plenty of people disable MDS either with the buttons or tow/haul. Anecdotal evidence would show that there isn't a higher percentage of lifter related engine failures with those engines. I have no idea of any real data on this. I'm going strictly by what I read in three Ram truck forums LOL.

 

[JHoward]

Note to Self: proofread 1st, THEN click submit.
I just realized my quoted post is inconsistent and makes no logical sense.
So... sorry for my confusion.

You have the capability to go back and edit your post(s)? I do ...