Because of the system design. There is not enough room in the heads to do this. The plumbing and valving are in the block by cam and lifters. The OHC design of the 4.7L does not provide enough space to add these components.

It does save me gas on the highway even with my Predator.

 

Hey lxman1, didn't you dissable your P.O.S. MDS with your predator? Coulda swore you did. :}

 

MDS: Multaple delusional system.

Works well on a charger, but not in a truck, turning over the od will disable mds, city mpg will improve, over 50 mph, shift into od ...

 

wow never knew mds was so ****ty lol . I guess thats cus ive never had it . I supopse to cant believe something is so great just cus ppl use it . And as for the hybrid yes dodge ram is coming in a hybrid mode in late 2009 early 2010. Its gonna be the two mode system with electric engine that is said to reduce fuel comsumption by 40% in the city and 25% overall

 

Bingo...even if they could come up with a new design for the MDS on a 4.7 it just isn't needed from an marketing point of view (that's all that matters to DCX). They made it for the hemi because the word hemi just screams gas guzzler in the minds of most potential buyers. With MDS all they have to say now is "Yes it's a hemi but it also shuts down to 4 cylinders when cruising".....and all the hippies rejoice. The 4.7 gets decent milage as is and the smaller displacement jumps out as better mpg to most people...including the 4.7 owners here

That's my opinion anyway

 

I did turn it off and my highway mileage dropped by about 1mpg. Above 55mph, is does kick in and out depending on the grade of the road, but it stays in longer with the 91 octane tune due to more torque I guess. Part of my 72 mile round trip to work is hilly and it stays engaged when going down hill which keeps 4 injectors from firing and saves fuel.

 

There is a reason for that high of gas mileage. Those POSs' have electronic throttle. We have an 08 avalanche with the 5.3, and its pathetic. at wot you don't go anywhere, you just make noise. My 5.2 has better throttle response, and I know for a fact that it runs quicker than the avalanche on the 1/8 mile.
I will give the damn things this though: they handle like a go cart.

 

Our 3rd gens have electronic throttel also.

 

Remeber this was the previous gen avalanche. I might not be an expert but I am pretty sure that an electronic throttle will hamper the speed of the truck sure throlltel response will be a little more dull but that is done on purpose to smooth driving dynamics and what not. Also this avalanche was a Z71 with 3.73 gears so it was snappy off the line and I am most certain it would do more than pull on any 5.2 ever could. I mean the avalaches have a good 75 to 100 hp on a 5.2.

 

I read on another web site that MDS was designed into the hemi from the beginning, it is cast into the block. they would have to redesign the 4.7 and that costs money. this site also said a smaller hemi might be coming.