kingofdodge7131

have something like that MDS? I know what they do in the gassers.... i dunno how they get it all to balance out but meh im not the engineer. But why not a diesel? Lookin at New megas...... basing this all off of over head. on my 04 its not more than 1 mpg off so it works. i can get 17 out of a hemi. and 18 out of the cummins. But if they would mds that thing. we would be doing good im sure

pronstar

I think MDS works for personal-use trucks (half-ton)...but not so much for working trucks.

MDS doesn't come into play if the engine has a good load on it...and I think most diesel engines are designed with the assumption that it will be put to work /loaded up for most of it's life.

kingofdodge7131

although that does make sense.... Still doesnt explain why it CANT do it. the hemi does it in a 2500.... and itsa "work truck" Who knows. Guess im greedy haha

Tate

VP trucks have a 3 cylinder idle, which is that same thing. I've never heard or seen it, but I've read that it sounds like the engine is coming apart. I don't think many people would want their engines sounding like that on the highway.

pronstar

True enough... but the Hemi is is also shared with the 1500.

One other thing to keep in mind:
Government CAFE (Corporate Average Fuel Economy) requirements apply to vehicles with a GVWR of 8,500 lb. or less. Which means that carmakers must use MPG-boosting technology for lighter vehicles, including half-ton trucks that fall into this category...but there's no incentive for them to do it for a heavier vehicles because they don't count against their CAFE requirements.

shonne

from what I have read recently, the decision to switch from full power to cruising mode is determined by the pcm. The pcm then monitors engine vacuum as the indicator of the vehicle's power demand. Diesel engines do not create an engine vaccuum, aka no throttle body and why exhaust brakes work. Now, having this work with an inline engine and with charged air, I would be impressed. I can only wonder what the mods like with MDS. A programmer would be a MUST!

I doubt there is not enough beer for a rational answer. I am sure someone here can explain this.

MikeyB

The Hemi in the 2500 does not have MDS. Only the 1500 regular and QC models have MDS.

For the MDS to properly work the intake and exhaust valves must be parked in the open position to remove the friction from the compression on the dead cylinders. Somewhat easy to do with hydraulic lifters. But not so easy with solid lifters like the Cummins. Plus the Cummins has 4 valves per cylinder whereas the Hemi only has two (and I think 3 for next year).

MikeyB

kingofdodge7131

The 2500 mega i just drove had it.... But thats neithe here nor there I wasnt aware that he hemi had Hydro rockers.. Not sure I said i dunno how it works exactly i think ha. Either way. It wasnt a war type thread. Just a lil rant of mine.

CNeubauer

Back in the mid '70s International had the 1468 and 1568 tractors which used a 550 cid V-8 diesel engine so they would cut down to four cylinders under light loads and alot of them were converted to run on all 8 all the time. That was along time ago using an all mechanical engine but in that application at least it didn't work out very well.

johnny5.9

The MDS only applies to 1500 truck the hemi does not have MDS in the 2500 or 3500.

I think MDS would not benefit a diesel for the reason that diesel engine components are too heavy to be rotating at any rpm over idle without generating power. The vibration this would cause would seriously affect NVH and longevity. Diesels can drastically reduce the amount of fuel injected when power demands are low, so precise fuel injection software is the key to efficiency not shutting off cylinders. This can all be done now but people are too concerned with quiet and smoothness. Advancing timing and eliminating pilot injection events would yield impressive economy but at the expense of diesel rattle which is becoming unfashionable.

rjm022

like stated earlier- the 2500 hemi's do not have mds-only the 1500's

cbtumedic

2500 does have MDS with the hemi, look here http://www.dodge.com/en/2008/ram_250...ility/engines/
Also, just because it didn't work in the 70's doesn't mean it won't work today, look at the old v-8-6-4 cadillac's they didn't work, but similar tech works now. But i believe it would be quite a nightmare to make it work in a truck that is intended to pull heavy loads.

johnny5.9

Dodge must have added the MDS feature to the 25 and 3500's. I asked when I was at the dealer buying my durango the salesman specifically said only the 1500 had the MDS. It's cool they all do now. I wonder if they changed the programming of it though. My durango won't stay in MDS with much throttle application at all and it has 3.90 gears. I can't imagine it would be any good in a heavier vehicle unless they made it less sensitive to throttle application.

rjm022

something new for the 08's. i stand corrected.

kingofdodge7131

Ha i wasnt gonna argue. It was the window sheet that said what it had. I called dodge a lil while ago to get he build date of my 2004. 2 dealers told me it was 12/6/2005 I bought it july 04..... I wonder sometimes


But yeah. I really dont NEED another diesel. just the bigger cab. My moms bonnieville gets 23 and my neighbors charger gets 19. the charger gets around ok in the winter being awd. but the bonnie no go. So i figured mega cab here I come