Just because I'm curious and somebody might know...

When MDS is active, the telescoping lifters don't open either the intake or exhaust valves, and the spark plugs aren't fired, but the piston is still moving in the cylinder. With the piston itself still active, won't there be added drag on the crank from having a vacuum in the cylinder (since no "intake" stage is performed)? Engine pistons always compress air, and don't usually create vacuums in the cylinder.

 

Apparently Limedust, the spark plugs still fire.
The other stuff..........it's been covered on here in an earlier post.
Can't remember what post it came in under though.
A search on MDS might pull it up.
Al.

 

Did a little searching since I first posted...

According to this article by Popular Mechanics, the computer doesn't fire the spark plugs during MDS operation, but I've read a lot of conflicting descriptions of how MDS fully functions. The article also states that the MDS function is activated in such a manner that exhaust gas is trapped in the cylinder, causing the piston to continually repeat a "compression" stage.

If you can link to the thread discussing the operation that would be appreciated. I couldn't find it.

http://www.popularmechanics.com/auto...tml?page=4&c=y

 

Here's another link to some more info :-

http://www.allpar.com/mopar/new-mopar-hemi.html

Enjoy.

Al.