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Unread 03-06-2011, 07:37 PM   #16
LuckRider
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Well, the MDS works up to 90mph in the computer, so you can go that 80mph you want. Speed limit is slower than that though.

In my Jeep, heck, 55MPH is fast. In my mom's, 80 is slow.

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Unread 03-07-2011, 08:22 AM   #17
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Quote:
Originally Posted by LuckRider View Post
I hope people find this information useful and informative.
Absolutely. This answered some questions I had in the back of my head, namely "what the hell is going on in the cylinders when they're "deactivated?""

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Unread 03-07-2011, 08:29 AM   #18
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I am glad it taught you something. I am VERY VERY slowly working on adding more articles like this to the FAQ posted in the sticky. My hope is to have a comprehensive overview of the entire vehicle. From what I can find, there is a factory service manual, but it is only in the dealership computers.
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Unread 03-08-2011, 09:35 AM   #19
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In our 07 5.3L Avalanche it's a joke. Here in Florida it NEVER kicks in and when we are in TN it only kicks in when I'm completely off the accelerator going down a mountain. I get about 17mpg hwy in FL about 15.5mpg in TN out of the Avalanche.
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Unread 04-25-2011, 02:34 PM   #20
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Quote:
Originally Posted by LuckRider View Post
just rolling through some old threads. i noticed that this is not a picture of a WK2 evic display. on the 2011+ grand cherokee, the eco light will be at the top of your EVIC.
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Unread 04-25-2011, 10:38 PM   #21
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Yeah, that is from a truck. I just posted for people to realize that it is right in the middle of the display (between the speedo and tach).
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Unread 04-26-2011, 05:50 PM   #22
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Quote:
Originally Posted by ram2 View Post
Why would I buy a Hemi to drive 65mph or slower?
I usually cruise at 75-80 on my interstate trips, and I assure you that ECO mode kicks in over 65 often, also. If you're not speeding up or climbing a hill, it'll kick in at higher speeds just as often as lower speeds.
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Unread 04-28-2011, 05:27 PM   #23
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To disable the MDS, put your shifter from D to 5 (as displayed on the EVIC or cluster). With the console shifter, this is just one hit to the left. With the column shifter you need to push the +- button - one time.

Your trans will still shift up and down automatically through all the gears.

This is helpful for those who wish to disable the MDS. It works great and it come straight from Hemi Engineers....
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Unread 04-30-2011, 08:23 AM   #24
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Interesting...I'm impressed we can control this.
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Unread 05-01-2011, 05:35 AM   #25
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Very interesting article - thanks alot for the effort. I was excited to see this technology in the hemi and it definitely factored into our decision to purchase. We have gotten used to the same system on our 2006 Honda odyssey and although I was suspicious at first, it really works. That vehicle gets 28 mpg highway with a full load of 7 people in it. ( and it doesn't feel underpowered, at least for a mini van.)

I had wondered ever since why this wasn't used in bigger engine vehicles. Makes all the sense in the world... Power when you need it, more efficiency when you don't...

Go jeep! Anyway / I'm in love with the 2011 GC - what a great truck....
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Unread 05-01-2011, 07:15 AM   #26
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Yeah, this system was in our 2008 Tahoe as well. The gas mileage wasn't as good as my 5.7L, but it was decent given the size of the vehicle/engine.
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Unread 12-22-2011, 05:15 AM   #27
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Why would I buy a Hemi and worry about gas MPG !
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Unread 12-22-2011, 06:04 AM   #28
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ECO will display any time the computer is in an economy setting. So when the VVT kicks into economy mode ECO will display as well as when it drops cylinders. That is how I understand it at least.
We would worry about mileage in the hemi because gas is $3 a gallon. It's the nature of the beast. I didn't buy it for good MPG obviously. But I sure can pay attention to it. I. Bought it for towing.
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Unread 12-22-2011, 08:38 AM   #29
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I've got the Hemi in my WK2, but call me a skeptic as far as the MDS types of systems are concerned. While I do get 21-24mpg highway with my Hemi 4x4 WK2, it's more to do with me using cruise control and keeping it around 65-70mph. A friend of mine has the same vehicle and gets 23-24mpg regularly driving the interstates on a regular basis. Around town I bump the shifter left to go into "5" and avoid MDS, and one day got onto the highway to see a friend down state and I still got 22mpg........in "5" without MDs ever being activated.

I'm sure MDS might add 1mpg but it isn't as big a deal as some think because on a big engine there are still pumping losses from the deactivated cylinders. You're not running as efficient as a 4cyl engine when you shut off 4cyl from a V8. It's kind of like the rpm arguments: it's not how slow your engine turns, it's how much power you need to maintain speed that matters. Whether or not it's at 1000rpm or 2000rpm, you still need to make X-horsepower to cruise at Y-mph. Aside from marginal pumping losses (an engine is essentially a big air pump), the reason 6cyl and 8cyl engines get poorer economy than a 4cyl, all else being equal, is due not to simply pumping losses and idle time but is also greatly affected by driving habits where people USE the extra power in the I6/V6 or V8.
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Unread 12-22-2011, 10:14 AM   #30
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We have the v6, and we are averaging about 21 on the highway right now... that means the MDS is actually working because the 3.6L is a much more efficient motor (not just that it uses less fuel, but the fuel to power output ratio is better).
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