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Discussion Starter #1
Hey everybody this is my first time posting at these forums, which are quite nice btw.

I've been reading up on the new HEMI quite a bit lately, more specifically MDS, but I haven't found out too much other than that it turns off 4 cylinders when the engine is not under load.

This question is more to satisfy technical curiousities more than anything. But I was wondering if MDS when activated (by that I mean 4 cylinders running, and four off) would cycle through the avaible 8 cylinders. By that I mean does MDS alternate which 4 cylinders recieve power during a stroke of the engine, or does the engine simply turn off the SAME 4 cylinders everytime MDS is activated.

Thanks for any insight
-Manris
 

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Discussion Starter #3
I know the cylinders don't shutoff, but they aren't supplied with the means to make power... they aren't supplied with fuel and a spark, but air does pass through them.

Thanks for an answer though, I figured that it be a p.i.t.a. to engineer a system that alternates which pistons recieve power, seems unnecessary.

BTW Rogelio I like the stripes on your Charger
 

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Manris said:
I know the cylinders don't shutoff, but they aren't supplied with the means to make power... they aren't supplied with fuel and a spark, but air does pass through them.
Actually, the system deactivates the valves and they remain closed. Any air/fuel that is "caught" in the cylinder is compressed and recompressed over and over, this creates a "spring" action that helps keep the pistons moving. Most likely there is also some factor of blow-by (air/fuel mix seapage past the rings) but probably very minimal. Since the computer shuts the spark off there is no ignition.

BTW - Welcome to the forum.
 

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I hope that this won't be the same headache as the 4-6-8 Cad motor that was a royal POS. Especially with Chrysler going back to a 3/36
 

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RT-DAYTONA-RT said:
I hope that this won't be the same headache as the 4-6-8 Cad motor that was a royal POS. Especially with Chrysler going back to a 3/36

the Caddy 4-6-8 was a joke... and it shook like crazy... from the test drives I have done in the Charger... alot has happened with this system in the last 20+ years... (edit: my father had a 4/6/8 caddy for 2 weeks, told the dealer when they fix it to call him and he will come buy the car again... they never called him)

Also... I went car shopping with my father (he is still not sure what he wants to get), he wanted to go to the Honda dealership to test drive the odessy.... which has a 3/6 system, like the hemi's 4/8...

light on the dash tells you when you are running on 3, and other then that light... you cannot tell... system works great...

So since honda went and gave people a light telling them when cylinder deactivation is occuring... why can't dodge do that?

I will probably do the mod for this light, per the instructions on the LX board...
 

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So would MDS cause "extra" wear on the 4 cylinders that are always on?

edward
 

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Discussion Starter #8
There are some great threads on this at www.300cforums.com. They know a hell of a lot about the inner workings of the new Hemi, compared to here (I'm judging that based on the number of responses i got from this forum, which is still great btw). I also learned about some other things I didn't know about. But one of the things i read is that MDS will turn off after 6 minutes so that the cylinders, pistons, etc... stay at some sort of acceptable operating temperature. It doesn't say how long afterward it would come back on. Basically what i learned is that the system is not used as much as i thought it would be, it also depends greatly on the terrain and your driving style.

But as far as your question goes... I used to worry about that myself...i do not think that increased engine wear will be a problem in those cylinders, especially if you are keeping a good oil change schedule. Maybe over the course of 500,000 miles it may start to become a problem, but not at 100,000 or 200,000.
 

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