I tried to search "MDS", but nothing came up. I keep hearing about a lot of people disabling their MDS system and am curious what the advantages and disadvantages are. Why do you disable MDS?

 

People that have aftermarket exhaust systems complain that there's a drone when MDS kicks in. Other people complain that they lose power due to MDS. In theory, MDS saves gas because it is running on 4 cylinders instead of 8 when you are maintaining a constant speed (such as on the highway). It's not supposed to kick in when normal city driving because you are constantly slowing and speeding up. I haven't had any problems with mine, but I don't have an aftermarket exhaust.

 

The only time I ever benefitted from MDS was on the highway going downhill or had a tailwind or going 30mph steadily on flat ground. MDS makes you press the gas quite a bit just to get out of it and then even more to downshift which actually yields worse gas mileage.
I have a Diablo Predator and get better gas mileage on their 91octane tune and the MDS disabled than the factory settings with the MDS enabled. I am seeing 2mpg more on a constant basis on the highway and 1.5mpg improvement in the city not to mention the truck has much more power.
These big trucks just aren't cut out for 4cylinders to move them through the air efficiently. Everytime I was on the highway and the MDS kicked in, I would gradually lose speed and then ofcourse the MDS would kick out, I would speed up and then it would kick in again. Very, very annoying for anyone with an aftermarket catback and there's simply no reason for that anyways. It would do it even worse with the cruise control set. I never noticed it with the factory exhaust on the highway, but I could feel the lag in the city. It wasn't until my Magnaflow catback until I learned why. You can hear and feel it kick in/out constantly. It's the worst idea I have ever come across.
The truck simply shifts so much cleaner and crisper with the mds disabled. It downshifts super quick with no hesitation like it did before. I will NEVER enable the mds ever! Most who disable it with a tuner never look back as there's no real benefit for it. It's all a gimmick for emissions and government regulation for "better" gas mileage. The computers are so well adaptive to your pedal response, it always uses the least bit of fuel possible in any instance.
Last week on sloppy 6" snow covered roads, I drove 23miles of half side roads at 40-45mph and half highway at 70mph all in 4wd. I was still able to maintain 18.3mpg on my read-out. Never even on the highway in 2wd on a dry day could I get that before. I am getting 12.5-13 in the city and that's with always using my car starter to warm up my truck. Before it was at 9-11mpg's.

 

I have a magnaflow on mine. Yea, at first MDS was irritating but now i dont even notice it. For me personally, its no big deal.

 

I too have the Predator and got rid of the MDS. Like DD said its great for highway driving but thats about it. I must drive worse then DD and I am running the 93 tune with Super and I get around 11 MPG but its hard to drive the stealth bomber slow.

 

Load in the 91 tune and you should see a descent gain in mileage. I really didn't notice much more power gain going from 91 to the 93 tune but I did see the meter running at about 9mpg in the city. I loaded the 91 tune back in and mileage is much improved. Try it for a tank of gas and see how you do!

 

Tuning the MDS out is the best thing i've done so far. The truck actually drives normal now and runs a lot smoother...it's like a new truck. Not to mention it doesn't sound like a damn copter anymore. My mileage is about the same on the 91 tune in city...slightly worse on the highway.

 

Worse??? I wonder why? Prob because you can't get your foot out of the added performance...lol

Also, don't be confused GOT HEMI44 The 91 tune the predator has is a performance tune and the 87 oct tune is the stock with added gas mileage and shift functions. There's no way you could not benefit more from their 87octane tune wth MDS disabled than the factory tune. I went from 280 miles to a tank to 320mile to a tank at roughly 22gal. from a preformance tune with mds disabled.

I think this is all getting off the beaten path.

I think if you did a poll strickly for the guys who have had the ability to disable MDS already, you will find that NOBODY would re-enable MDS after shutting it off.

 

Here's some info on MDS, even has some pictures of a cutaway that shows how MDS works, need to scroll down a bit:

http://www.allpar.com/mopar/new-mopar-hemi.html

MDS works well for me, for both around-town driving and highway commute. I'm averaging 18.5-18.8 mpg on a tank, usually includes 2 180 mile round trip highway commutes and 3 to 5 short trips between buildings at work or running errands at home. Round trip highway commute only, keeping under 70mph most of the way (under 65 mph on gradual inclines, trying to keep MDS on), I get 19.7-20.4 mpg.

I don't notice any lag in response; MDS is supposed to react withing 40 milliseconds, which is certainly below my threshold of detection. But that's just me, I'm getting old...

 

MDS is a dog. Can't believe Detroit came up with something so backward.

My 08 HEMI reprogramed with a Diablo Predator and MDS disabled, runs 100% better. Gas milege seems to be better, if I can keep my foot out of it.