Another MDS Question..... Oh NO! Not Again?

[SniperDroid]

Yeah, again. I read through as many MDS threads as I could stand, reading complaints about the noise and loss of power. More people seem interested in turning it off than anything else. I would like to know a little more about how it operates. I watched some videos on YouTube, and I understand the basic operation. But does it always turn off the same 4 cylinders? Seems that would put a lot more wear and tear on the other four always running cylinders and components....? Are the MDS lifters what cause the dreaded HEMI KNOCK? IF the MDS has been around for a while, how well does an engine so equipped hold up? I can understand the desire for more economical operation, but after all, IT'S A TRUCK! I use it primarily for towing a Travel Trailer, so economy is not what is foremost in my mind. In Tow/Haul mode it is off. Have there been any long term detrimental effects of using it in daily operation?

Sorry for the length, but I really couldn't find the answers to these questions.....

 

[Nick_rp]

You probably know as much as i do but my '12 is at 160k miles and have never had any problems with MDS causing any sort of failure. Ive had the same thoughts about uneven wear and stress. I delved into the bottemless pit that is MDS in search but once and ran away screaming and crying.

Actually, i unintentionally disabled my MDS when i hollowed my cats and thats the only reason i haven't fixed the CIL yet for the downstream o2s. Its my understanding they only moniter co2 output and dont handle anything with the mix. Works for me

 

[2012RAM1500RT]

I won't argue either way on it, I mainly turned it off all the time because I have an exhaust system where I can hear it kick in and out and didn't like it. Now I have a tuner so I had it turned off permanently. I see no difference in fuel mileage which I understand is it's main purpose is to make it better on fuel. If I lost 2 miles to the gallon I may consider turning it back on and put up with the kicking in and out noise but for me I have no noticeable difference. By the way I have 136000 miles on it and no cam or lifter issues SO FAR!

 

[mikeru]

There is conflicting information regarding whether or not MDS causes cam/lifter issues. I tend to believe there would be more wear on the components for the cylinders that are affected by it. But I honestly don't really know one way or the other. I see the same results as 2012RAM1500RT. No appreciable difference in fuel economy with or without MDS. Because of that, and my aftermarket exhaust, I disable MDS every time I shift into D.

 

[HEMIMANN]

Since nobody seems to know exactly what causes the lifter and cam failure, nor how preventable it is, I'm leaving mine active in hopes of providing more oil to the lifter rollers when the system is in V4 mode. You can read up how the system operates elsewhere.

One guy that had to replace his engine had a shop custom build a rebuilt Hemi by machining larger head drainback holes, removing MDS pilot valves, installing non MDS lifters. This configuration provides oil to the lifter bores and rollers all the time. I'm still unclear whether the MDS oil galley feeds only the MDS lifters or all lifters.

 

[Troutman561]

I feel like the MDS crap people complain about is.. crap. It’s a theory that it causes lifter failures. And the noise/ power loss is being nit picky. Yea you can hear and feel it sometimes. But what, does it take .3 seconds for it to activate all 8 cyl when you touch the pedal? These complaints from what it seems are equivalent to the non-ram owners (and some owners) complaining about the rotary knob for shifting like it’s some sort of non-manly thing.

 

[mikeru]

I feel like the MDS crap people complain about is.. crap. It’s a theory that it causes lifter failures. And the noise/ power loss is being nit picky. Yea you can hear and feel it sometimes. But what, does it take .3 seconds for it to activate all 8 cyl when you touch the pedal? These complaints from what it seems are equivalent to the non-ram owners (and some owners) complaining about the rotary knob for shifting like it’s some sort of non-manly thing.

Thanks for your opinion that our opinions are crap. I'll file your opinion into the same round bin you filed ours into.

 

[Firebird]

I always disable MDS in town, use it on the hwy. I hate the sound and lugging.

 

[Fatbob Frank]

I wish it wasn't standard equipment!
If I wanted to drive a 4cyl truck I'd have bought a Chevy...

 

[ramffml]

There was a video posted here(?) a while ago where I guy goes into detail on how it works, all the parts are still moving the same way they would with MDS inactive, accept the valves remain closed, trapping the air/fuel mixture inside it which causes it to act as an air spring.

But I do feel the engine is probably "working harder" in the same way that lugging an engine at too low of an rpm is causing strain. Neither sound like good ideas too me but I'm just a layman so feel free to write off my concerns

It also jerks and tugs going in/out, and the experience is not smooth or linear when trying to get a bit of acceleration.

The rest of the truck is so smooth and refined (for a truck!!) and luxurious etc, no way I'm putting up with a jerky/droning truck so that MDS stuff can stay off thank you very much.

 

[mikeru]

There was a video posted here(?) a while ago where I guy goes into detail on how it works, all the parts are still moving the same way they would with MDS inactive, accept the valves remain closed, trapping the air/fuel mixture inside it which causes it to act as an air spring.

But I do feel the engine is probably "working harder" in the same way that lugging an engine at too low of an rpm is causing strain. Neither sound like good ideas too me but I'm just a layman so feel free to write off my concerns

It also jerks and tugs going in/out, and the experience is not smooth or linear when trying to get a bit of acceleration.

The rest of the truck is so smooth and refined (for a truck!!) and luxurious etc, no way I'm putting up with a jerky/droning truck so that MDS stuff can stay off thank you very much.

That's pretty much the same description of MDS that I've read, except there is only air that's trapped, not air/fuel. The injectors are shut off when MDS goes active. Otherwise, your engine oil would get contaminated with fuel.

 

[Jeff Strader]

There are several rumors and false claims, stating that the Chrysler MDS System was created in order for the Hemi to achieve better gas millage......"I don't care what you've found on the internet or what your best bud tells you, that is 100% TOTAL BS!"...............The actual facts pertaining to the creation of the MDS System was for and is, for one reason alone (POLLUTION). I worked in the automotive production industry for years. I know exactly why it's there...............The 5.7 Lt/345 Ci V-8 Hemi, is a POLLUTING HOG!. It had such a high pollution rating on the EPA scale, that the ONLY way that engine could be used in that operating form, was to reduce its overall pollution rating and the best way to do that was to borrow an idea already in use by GM. GM devised a way to do so. They created a system to reduce emissions by reducing the # of operating cylinders at a given rpm. Chrysler followed in the same suit with their MDS System. This is knowledge I have acquired over my many years in the industry, that is NOT common public knowledge. The first thing I did when I acquired my 2007 RAM 1500 Bighorn 5.7 was to turn that worthless MDS GARBAGE OFF!. My mileage went from around 16-17mpg up to 18-20mpg.............however, don't take my word for anything, believe what ever you want.

 

[2012RAM1500RT]

Don't take this as an argument but just a question, how can I put out less gas (you said you get 2 to 3 MPG more with MDS turned off) in more miles and put out more pollution if the MDS is for pollution only? I'm not claiming anything, I didn't see any difference on mine myself but not saying anyone else doesn't. Mine is off and staying off.

 

[CG2742]

When mds is active doesn’t the remaining 4 cylinders actually work harder? I thought more fuel and air was added to help the truck along. Mds is garbage if you ask me. I drive all highway at 80-85 daily. Mds gave me less mpg than running 8 cylinders. Hand calculated

 

[SniperDroid]

The first thing I did when I acquired my 2007 RAM 1500 Bighorn 5.7 was to turn that worthless MDS GARBAGE OFF!. My mileage went from around 16-17mpg up to 18-20mpg.............however, don't take my word for anything, believe what ever you want.

Okay, that's the kind of information I'm looking for, but you didn't say how you turned it off...!

 

[HEMIMANN]

When mds is active doesn’t the remaining 4 cylinders actually work harder? I thought more fuel and air was added to help the truck along. Mds is garbage if you ask me. I drive all highway at 80-85 daily. Mds gave me less mpg than running 8 cylinders. Hand calculated

Somewhat. MDS is active only when engine is lightly loaded overall.

 

[ram1500rsm]

I’ve disabled the 4 cyl crap via tuning in All the applications that had such a system since 2009, the RAM happened to be one of them. Never had any issues.

Most important my mufflers doesn’t sound horrible because there is no more 4 cyl operation. To those of you with performance mufflers if you knew how bad your truck sounds from the back when mds is active you’ll want that pos system disabled rigth away. Go ask your wife or friend or relative etc to drive your truck while you hear your truck from behind. You’ll appreciate having 8 cyl all the time

 

[mikeru]

I’ve disabled the 4 cyl crap via tuning in All the applications that had such a system since 2009, the RAM happened to be one of them. Never had any issues.

Most important my mufflers doesn’t sound horrible because there is no more 4 cyl operation. To those of you with performance mufflers if you knew how bad your truck sounds from the back when mds is active you’ll want that pos system disabled rigth away. Go ask your wife or friend or relative etc to drive your truck while you hear your truck from behind. You’ll appreciate having 8 cyl all the time

I have no doubt you're right about that. But I don't care if other people think it sounds bad. I care how it sounds to me. And since I can hear it when I'm driving, I will be disabling it. I just won't use a tuner since I'm still under the factory warranty for a few more years LOL.

 

[Troutman561]

Thanks for your opinion that our opinions are crap. I'll file your opinion into the same round bin you filed ours into.

You're welcome. Does anyone have any prof there is widespread, long term issues with MDS? Other than hearsay?

 

[2012RAM1500RT]

You're welcome. Does anyone have any prof there is widespread, long term issues with MDS? Other than hearsay?

It works both ways, is there any proof that MSD doesn't cause long term issues. Mine will stay off until there is. If there's no harm either way then neither way is wrong.