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Old 11-25-2013, 11:46 PM
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how do you know when its only using 4 cylinders?

I have seen this thread but searching 4 8 cylinders nothing comes up. How do you know when its only running on 4 (deactivating the other 4). Do you see this as a potential maintenance nightmare later?
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Old 11-25-2013, 11:49 PM
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Re: how do you know when its only using 4 cylinders?

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Originally Posted by yjbeach View Post
I have seen this thread but searching 4 8 cylinders nothing comes up. How do you know when its only running on 4 (deactivating the other 4). Do you see this as a potential maintenance nightmare later?
Any time the ECO symbol is on the dash your running 4cyc no way to turn it off unless you use a tuner like the Trinity from Diablo Sport
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Old 11-27-2013, 12:57 PM
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Re: how do you know when its only using 4 cylinders?

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Originally Posted by xJoshxx View Post
Any time the ECO symbol is on the dash your running 4cyc no way to turn it off unless you use a tuner like the Trinity from Diablo Sport
I think the more correct why to respond would be, any time the ECO switch is enabled, you have the potential to run on 4cyl (MDS). From what I understand, MDS will only come on when you're cruising at ~50 MPH up to about ~80MPH. Some have claimed (with LED indicators) that MDS even comes on as high as 85MPH.

I don't believe there is a way to show MDS is working or not, without modifications. IMO, this info should show when viewing the Economy screen in the EVIC but alas, it doesn't as of now.
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Old 11-27-2013, 12:58 PM
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I was wondering about this as well. I haven't been able to see any visual indication of what is actually going on.
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Old 11-27-2013, 01:26 PM
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Re: how do you know when its only using 4 cylinders?

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Originally Posted by xJoshxx View Post
Any time the ECO symbol is on the dash your running 4cyc no way to turn it off unless you use a tuner like the Trinity from Diablo Sport
Some years and versions don't have that little symbol available as an option any more.
e.g. current 2014 UConnect.

Bummer, as it would be a source of amusement on cross country drives to either try to keep it on--or off as the muse strikes one.

I'd actually prefer a less subtle indicator such as turning the display a tree hugger green or something.

The pistons are still moving so they would be getting lube. The valves are shut to create an air spring effect. Never heard of long term maintenance issues with MDS and it IS one way to extend the sales life of larger engines until they are banned forever.

Does anyone know if it changes the set of 4 cylinders it deactivates to keep from any possible effects by always using the same ones? It would be trivial to implement, but that doesn't mean it would occur to anyone to do so.
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Old 11-27-2013, 02:33 PM
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Re: how do you know when its only using 4 cylinders?

Install an aftermarket exhaust, unfortunately you'll know when it engages. Gets annoyingly loud making parts of the truck rattle.
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Old 11-27-2013, 03:45 PM
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Re: how do you know when its only using 4 cylinders?

According to what I read, I think somewhere on the Jeep web page, it always shuts off the same four cylinders. They claim that high mileage engine tear downs show no excessive mismatch in wear between the two banks.


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Old 11-29-2013, 10:50 AM
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My 2012 JGC has an "Eco" light on the instrument panel. It lights up when 4 cylinders shut down. Always wondered how this works. Recently found this explanation.

www.wk2jeeps.com/wk2_engines.htm#mds
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Old 11-29-2013, 11:10 AM
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Just for clarification. The 2014 v8 will always have the opportunity for MDS to kick on at times in auto mode. Using the Eco mode allows MDS to engage on a wider range... MDS has the potential to kick in when in auto mode it cannot be disabled (without tuning).

I found this out because i could hear the MDS kick in even with Eco mode disabled. Give me a sec to gather more information
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Old 11-29-2013, 11:21 AM
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"MDS is active in both auto and eco modes. The mds has a wider range of operation in eco mode that is why it is more noticeable. It is disabled in Sport and track modes. 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 for '14. "
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Old 12-03-2013, 10:01 AM
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Re: how do you know when its only using 4 cylinders?

Replace your muffler with a Magnaflow. When it start farting, MDS kicked in.
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