Am shopping for a Quad Cab Hemi and notice the Hemi MDS VCT is now "discontinued" -- which even I understand means it ain't made any more. So then I run across a Hemi MDS WT. Is the WT the latest version? What is the change, the difference? Should I avoid the MDS VCT?

 

See VVT below

2009 Ram HEMI Upgrades - 390 HP/407TQ

VCT Variable Cam Timing: Valve controls oil flow to unique camshaft sprocket with a phasing device that advances/retards timing according to oil volume provided by control valve. NOTE: Discontinued to cut production cost. If you find one with VCT grab it cause it'll run stronger. VCT is common in F1 racing.

SRV Short Runner Valve (active intake manifold): Port length changes based on rpm's. Valve closes @ low rpm's for improved low-end TQ (long runners). Valve opens @ high rpm's diverting flow to center of manifold for increased HP (short runners). Cylinder heads improved to increase flow.

MDS Multiple Displacement System: Now operates over wider rpm range increasing efficiency.

VVT Variable Valve Timing: Increased engine breathing through the entire rpm range by varying points which valves open/close in conjunction with piston position.

 

VCT = No 'Fuel Saver Light'
VVT = 'Fuel Saver Light'

 

VCT = nothing to do with the MDS light.

 

how do you go about finding out which version you have?

also this MDS light. where is it located? obviously mine doesn't have it.....
but then again, when driving down the interstate i didn't notice any fluctuation in rpm as i did with my '06 charger....

 

Hmmm, I just checked my window sticker and sure enough, I have the VCT model with no MDS light. So bountyhunter, why is VCT better than VVT? Anybody else know?

 

That's interesting. I was wondering why I have never seen any kind of fuel saver message or light. I would assume that the fuel saver light/message has to do with MDS more than anything, so why would they include it on a MDS VVT motor and not a MDS VCT one?

 

I was just reading the wiki page on VVT and this is what they say:

So if that is true, then VCT might get slightly better horsepower but less gas savings? Which might explain why there is no MDS light on the earlier trucks?

 

Here is the link for VVT and VCT:

http://en.wikipedia.org/wiki/Variable_Valve_Timing
http://en.wikipedia.org/wiki/Variable_Cam_Timing

 

The 2009 Hemi engine is a new version of the Hemi, as you all know. It launched as a VCT only. Some hardware changes were made and a different MDS cal came out to make the engine a VVT. With these changes the 'Fuel Saver Light' was added.

New Rams are now 100% VVT. I believe the only vehicle the VCT is still available on is the Callenger. You get a VCT with a manual and a VVT with the auto. I am not completely sure why, but I have heard that the MDS cal in the VVT causes problems with the manual trans. That is just what I heard though. Go the Dodge website and build a Challenger and notice how there are two hemi engines and it will change depending on what trans you select.

Nothing is wrong with either one, its just that if you buy a Ram with a VCT, you will get an earlier version without the Fuel Saver Light. Simple as that.