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cloud11244 11-24-2011 01:53 PM

MDS droan
I know this topic has been covered before but I want to make sure I understand what is happening.

SITUATION: cruising on highway at 70 MPH with cruise control. ECO light on and I hear a slight droan in engine/driveline. RPM is about 1600 rpm. I assume MDS is on. Slight incline comes up and ECO light goes off and droan goes away. I assume eight cylinders are working at this point.

Also, if I tap shifter to left, rpm shoots to 2100 rpm and 5 is displayed. RPM settles to 2000 rpm. ECO light is off and there is no droan. (Transmission TSB has been applied so it acts like a 6 speed).

So seems that droan is associated with 4 cylinder operation in MDS. Is it enging lugging with 4 cylinders trying to move a 5000 lb JEEP?

ryorde 11-28-2011 09:15 PM

Re: MDS droan
You are correct.

cloud11244 11-29-2011 05:58 PM

Re: MDS droan
Thanks for your confirmation. I guess I could run in 5th gear instead of "D", and have 8 cylinders working all the time. I wonder what the difference in MPG would be if I cruise at 65 MPH in 5th gear (at about 2000 RPM) rather than in "D" (at about 1600 RPM)? On the other hand, having bought the HEMI, I wasn't really too concerned about gas mileage. Guess there would be more wear and tear on the engine running at higher RPM.

ryorde 11-29-2011 11:16 PM

Re: MDS droan
FWIW, I don't notice much difference at all. I had the same concerns you do, but after 20k worth of test mileage I'm not to worried any more. MPG was difficult to test when you consider all the variables involved. I only noticed about 1 mpg difference at best. To test for wear, I have sent my oil to a lab for analysis about every 5k miles. My TBNs have averaged about 2.0 after 7500 miles. Oil contents have also been well within acceptable limits.

kazak 11-30-2011 10:21 AM

Re: MDS droan
not to hijack the thread but what does MDS stand for?

PECo 11-30-2011 12:11 PM

Re: MDS droan
MDS Stands for Multi-Displacement System, which is a cylinder deactivation system that is designed to improve fuel efficiency:

And it should be "drone", not "droan" [sp]. :rolleyes:

kazak 11-30-2011 08:47 PM

Re: MDS droan

cloud11244 12-03-2011 08:48 AM

Re: MDS droan
I have been experimenting with running my Overland in 5th gear (not in "D"), both city and highway. I like the feel of 8 cylinders working all the time, avoiding MDS with 4 cylinders trying to move this beast, and the associated slight drone.

nosfed347 01-14-2012 08:06 PM

Re: MDS droan
I have an 11 Grand with the hemi. I have brought this thing to multiple dealers and they all have said the same thing, it is MDS. On a long drive it gets so bad that the shifter will have a slight vibration and the dash. No other jeep that I have driven does this, but mine just started in the last 10k miles.It was some what confirmed when I test drove the vehicle while the deactivating the MDS. I did this by unplugging the MDS solenoid connector behind the drivers head. They cel light came on but the drone went away, or not as noticeable. I believe that it is in the exhaust and I am wondering of the corsa exhaust might help with this problem. Any ideas on the exhaust swap? I am also going to hang a weight from the exhaust at various places to try and cancel it out.

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