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lol on the late...
yeah i dont see any eco light , just to clarify for me so wether i press the eco light or not in auto it will cut in not matter what ? Or is it a more economical map with the eco button pressed as well?
damn they make a complicated car.
 

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MDS is always active in auto and eco modes. The only difference is it has a wider operating range in eco which allows the vehicle to get better fuel economy, at the expense of some drive ability and nvh. There are changes in the transmission shift pattern to support this as well. There is no eco light in the dash that comes on during mds mode anymore.

Next time I'll know not to post a response if it's more than 12 hours after a question has been asked....

J

Sent from AutoGuide.com Free App
 

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Special hydraulic lifters are used on four of the cylinders. They are
controlled by solenoids. Each of the designated cylinders has its own
solenoid which controls two lifters. When the solenoid is energized, oil
under pressure is permitted to flow to the side of the lifter. This
causes a lock pin inside the lifter to compress. When the lock pin is
compressed the lifter contracts and its length is reduced. At its
reduced length the lifter is no longer able to open the engine valve.
To preface this question, understand I'm just a caveman, frightened and confused by MDS and eco buttons. I know the HEMI is an amazing engine, but with four cylinders regularly doing less work than the other four, wouldn't common sense dictate that eventually you'll end up with unevenly worn cylinders?

Maybe "eventually" is 500k miles I need to worry about this as much as if Mr. Fusion and a flux capacitor will be compatible with my 392 in 50 years, but I'm curious nonetheless.

(and yes, this caveman can Google, albeit poorly, and found nothing).
 

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I'll try to find the source, but I've read that numerous testing have been completed to see if running in 4 cylinder mode would have any long-term adverse affects. It does not.
 

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Well the SRT rep got back with me and Phil was right.

Just a few simple tips can help owners of Chrysler Group engines with
Multi-Displacement System (MDS) get the most fuel mileage possible from
their 5.7L HEMI V8 engine. The customer does not need to drive in a
certain way to realize a fuel economy improvement with MDS but these
driving habits can maximize their fuel savings with this technology.

?Keeping speeds to 65 mph or below - MDS uses four cylinder mode most at
these speeds
?Use cruise control -- this helps maintain a steady speed generally
allowing the HEMI to run on four cylinders for longer periods
?Accelerate more gradually - the HEMI will provide V8 power whenever it
is requested by the driver
?Use a steady throttle whenever possible - this maximizes four cylinder
mode"
:rofl:

Keeping speeds lower than 65
accelerate more gradually
steady throttle...

HAVE THEY EVER DRIVEN THIS VEHICLE?:rofl:
 

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I'll try to find the source, but I've read that numerous testing have been completed to see if running in 4 cylinder mode would have any long-term adverse affects. It does not.
According to this data, the engine was designed for the operation and my guess is that they have a routine which cycle through the cylinders to even out wear/temps/etc.


http://www.wk2jeeps.com/wk2_engines.htm#FEATURES
 

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Not trying to call you out but where did you hear this? I'm pretty sure MDS can activate on a 2014 even if the ECO button is not lit up. Pushing the ECO button makes MDS come on more than normal (along with transmission shifting early).

Copy & paste from wk2jeeps.com:
" Standard Fuel Saver Technology and a new-for-2012 active valve exhaust system allows four-cylinder operation to engage over a wider rpm range, to deliver both improved fuel efficiency - an estimated 13-percent increase on the highway - and an extended range of approximately 450 miles on one tank of gas.

Of course, even SRT owners sometimes appreciate driving more fuel efficiently. For those times, the 2014 Grand Cherokee SRT features an innovative Eco Mode that optimizes the transmission's shift schedule and expands the range of Fuel Saver Technology, which - when conditions are right - deactivates four cylinders to conserve fuel. Eco Mode is available in Selec-Track auto mode. Throttle mapping, transmission shift schedules and Fuel Saving Technology work in combination to achieve maximum fuel efficiency."

Jeep Grand Cherokee WK2 - 2011 Grand Cherokee engines

So if you are driving down the highway in AUTO non ECO Mode it will still enter MDS just on a more limited basis.
Very clear and in detail explained.
Thanks for your patience and time.
Thank you, this makes sense and would explain why it seems to come on at times. I hate to be picky but now I wish we had the option to display an indicator for when MDS does kick in...
Hi CLStech
In reality you have your desired option when you change your cluster display into fuel economy display, you will see 4 CYL in the lower center of the cluster when MDS is engaged.
 

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I wonder how bad the MPG would be with it completely defeated...
I've turned the MSD on and off during steady-state cruising on flat ground and have seen a 1.5mpg delta on the MPG readout.
I'll pay the few extra dollars at the pump to get rid of that irritating noise/vibration.

Also, there is no "ECO" button in my SRT.
 
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