For the guys who think deactivating the mds via a tune is a good idea

Wild one said:

I'd lay odds if he's driving it like Grandma,that's probably got more to do with it,then turning the mds off,lol.The Hemi's not an engine that takes kindly to being babied,they'd rather you drive them like you stole it,lol. Running around town just above idle means the mds system never activates

Click to expand...

Bmags said:

FWIW, I’m at 102k, last 50k have been without MDS via a tune, and before that I was disabling with the steering wheel buttons.

Click to expand...

Wild one said:

Keep us updated on it then,as that's a scenerio i've been curious about.

Click to expand...

crackerjack1957 said:

I'm a little confused also if this info is correct from Summit Racing.



So MDS solenoids are open when MDS is activated allowing oil pressure to decouple lifters.
MDS solenoids are closed when all lifters/valves are working on all 8 cylinders.
So how can this be bad on stock engines?

I can see how plugs could help flow on non-MSD cams/lifters by not flowing around/thru solenoids.
But cutting MDS off should not harm valvetrain by the above info if it is indeed correct.
I've been wrong before so someone show me otherwise.......LoL

Hemi Engine Tech - Multi Displacement System (MDS) · Help Center

Click to expand...

Wild one said:

I don't know if i'd say its a recipe for failure,as lots of guys do defeat it,and make lots of miles with it defeated,but it's definitely not the right way to delete it.
As evidenced by this thread,there are quite a few guys who are defeating it with the +/- buttons on the steering wheel,and haven't seen any issues.
I think a bigger recipe for failure is not staying on top of your oil change intervals,and using a good quality oil filter,and long idle times.
There is a caveat though,as i don't know of anybody who's deleted it via just a tune or using the steering wheel buttons,and made a 100,000+ miles,with-out a lifter failure.
I'm hoping somebody who has made it over a 100,000 miles with MDS deleted via a tune,and hasn't had a lifter failure,will post.
Im curious if anybody has turned it off via a tune at say 60 or 70,000 miles and then made it to 160,000+ miles with it just defeated via a tune

Click to expand...

DILLIGAF said:

You ilde time wouldn't matter when your tuned. FRP raises the idle speed . So we always have 45-50 psi at idle

Click to expand...

Bigskyroadglide said:

Agree all my idle speeds are at 750 rpm

Click to expand...

Wild one said:

As Dilligaff stated raising the idle and driving it like a bat out of hell is going to make a big differance in cam life.

Click to expand...

Bigskyroadglide said:

Ok, my combination of bad choices is actually paying off. That rarely happens....

Click to expand...

mikeru said:

After spending some time doing my assigned homework I've come to my own conclusions concerning this. These are my own conclusions. I am in no way looking to convince anyone to disable MDS on their own truck.

First, in my own opinion, disabling MDS isn't any more likely to kill lifters than leaving it on. I based this on the fact that they designed these engines such that the lifters are lubricated with pressurized oil regardless of whether MDS solenoids are open or not. Oil galleries supply constant oil flow to the lifter chambers.

Second, when MDS is active there is additional pressurized oil supplied to all lifters. Since the design of the engine already allows for sufficient oil flow this additional oil is not needed for lubrication. If there was/is a problem with insufficient oil flow you'd see significantly more lifter/cam failures, especially with those who use tow/haul or disable MDS. My estimation is that MDS activates on possibly 10% of my drive to work and 30% of my drive home. My engine should have died long ago if there was insifficient oil supply to any parts of the engine.

Third, my question is what would be considered sufficient oil flow for reliable engine operation? This to me is the meat of the discussion. The general consensus in this thread and in some youtube videos seems to be that there is insufficient oil being delivered to the lifters/cam. I would look to the designers to make that determination. No car company is going to design and offer engines that are oil starved in vehicles for 20 years and be successful. Those who say "they design them to fail after the warranty expries" are basically grasping at straws. Tons of people purchase extended warranties, and the car maker is still on the hook for the repair costs. Finally, My opinion is that these failures seem to have more to do with the design of the lifters. Tiny needle bearings were used that don't seem to have the durability that larger bearings would have. Which they apparently corrected around 2017. Audi had a similar issue with the design of the roller rockers used in one of their engines, which was quietly solved around 2019 with the use of larger needle bearings. But like with the Hemi, there are plenty of those Audi's still on the road with that design. So in the end you probably can't just point to one thing and deem it the cause.

When it comes to the actual cause of engine failures, there isn't much actual reliable data out there. There are plenty of opinions though. While I appreciate warnings such as that provided in this thread, I would encourage people to do their own research if they really want to learn about their trucks. By all means, consider what is presented in the thread, but temper it with your own research. And make decisions based on whatever knowledge was gained from that. But most importantly, maintain your vehicle as best you can, and enjoy the heck out of driving it.

Click to expand...

Wild one said:

Lots of guys have disabled the mds via tune or steering wheel buttons,and haven't had any lifter issues,so that's one thing to take into account. Did you see the lifter scoring on the sides of the lifter about the 14 minute mark in the 2nd video Mike,the scoring would lead me to think there is a lack of oil to the lifter bores at times though,otherwise there'd be no scoring marks on the lifter body.
I agree though staying on top of your oil changes,and using a good quality oil and filter,are still one of the best things you can do to maintain a hemi

Click to expand...

HEMIMANN said:

This is why I leave MDS on, except when towing (when I'm not stopping much so crank is running @ highway speed and splashing cam).

I think it was @Hemi395 that noted his ticking was less with MDS on?

And to think all this b.s. was all due to marketing, the EPA, and bean counters - marketing because the only benefit to a Hemi valve train is for racing rpm, EPA because of imposed CAFE mileage regulations causing engine makers to do dumb stuff like this, and finally the engine makers for going ahead with throwback Hemi anyway, getting a bunch of people to buy, and pretending "Hemi tick" is normal and hiding engine failures.

What an absolute cluster fuch of a product introduction.

Click to expand...

Ram1958 said:

I turned the ECO light option Off in a buddies truck. To this day he swears the truck runs better and has more power. Don't see the light , Don't notice the cylinder change.

Click to expand...

Ram1958 said:

I turned the ECO light option Off in a buddies truck. To this day he swears the truck runs better and has more power. Don't see the light , Don't notice the cylinder change.

Click to expand...

mikeru said:

Yeah, I watched that video too Rick. I don't think we can come to any conclusions about the lifters he used in that video. He doesn't mention anything about the history of them other than to say they were lifters he had laying around from when he used to replace them. We have no way of knowing how many miles were on them, whether the owner kept MDS active, or even if they came from the same engine. I'm not sure I would even consider that scoring to be honest. The fact that he doesn't mention anything about it tells me that he didn't think it was consequental to the topic of the video. The lifters all have similar wear/scoring in the same general location. But that's my take on it.

I will say that I can't think of a scenario where more oil flow is a bad thing. And his solution near the end of his video sounds like an interesting experiment. I'd really like to know what the designers of this engine would have to say about this topic if they could. In the end, for me at least, I'll never put enough miles on this truck to know if I caused any damage by disabling MDS. We've had this truck for over four years and haven't even hit 20k miles yet. We rarely keep any car or truck for more than 5 years. In fact mama has her eye on the new Ramcharger, although I'm not sure I'm ready to go there quite yet.

Click to expand...

Wild one said:

As H stated turning the eco light off in the 4th Gens doesn't turn off MDS.All that light means,is you're driving in an economical manner.My truck has no MDS solenoids or the wiring to them,and it still turns on the ECO light

Click to expand...