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A question about the new HEMI and MDS

2003 Views 9 Replies 7 Participants Last post by  JSA 007
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
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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
There are some great threads on this at 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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i believe there is a good amount of talk about this in this thread... pretty long but a good read for the most part if you are curious about the effect MDS has on fuel economy and other stuff
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