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Discussion Starter #1
yes i own a 4.7, no i am not dissing the hemi, a salesman just pissed me off when he brought his new hemi to poker and tried to sell me on mds.


if my 4.7 dies on a grade at 55mph doing 1500 rpm and needs to reach for 3rd, how does a hemi (with its crank still turning 8 cyliders) run on 4 cylinders at sub 2000 rpm on the flats.

hemi is like 345 horse(on premium gas): divide by 2 = 172.5 minus parasitic losses of turning 4 unused cylinders, estimate of 15% = 130 hp

so a 130hp 2.9 litre 4 banger pushing a 5500 lb 4x4 truck down the road at just over an idle?

to me this sounds like a placebo.

so mds must only run when running down hill or with 75mph tail wind. . is that it. and thats 20% fuel economy?????? how???

and does mds run at idle? if so wont cylinder cool and doesn't a cold plug(s) carbon up or foul? isn't that harder on an engine.

why doidnt they just kill al 8 cylinders at idle or downhill and call it a hydrid . . . . like chevy did

and i'll pickup 10% better fuel econ with midgrade on a hilly or heavy ride


no this not a slam hemi forum or 4.7 praise forum, i just want hear how this mds could actually benfit anyone beside a mecanic( and i bet it even pisses them off )

just my 2 cents.
thanx for reading
 

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It only seems to activate when at very light throttle but it works. I also believe it's a useless feature for a big truck.
 

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It wouldn't carbon up the plugs because it shuts off the fuel as well.
 

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Useless or not, DCX wouldn't of put the MDS in place if it did not serve its purpose.
On the other hand, I also agree that the MDS is usless for a heavy vehicle considering most trucks are used as trucks.
 

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It doesn't shut down the same four cylinders every time. They alternate so no one cylinder is left without combustion longer than any of the others.
 

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JeremyJ said:
It doesn't shut down the same four cylinders every time. They alternate so no one cylinder is left without combustion longer than any of the others.[/QUOTE

Yes it dose shut down the same cylinders each time, as strange as it sound.
 

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It has to shut down the same cylinders since the lifters are special and will park in the open position when the MDS kicks in.

MikeyB
 

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I think it works well as far as gas mileage goes. I had an '04 and this one gets better mileage. The MDS will kick in in 1st gear if I drive it normal, the only way I know this is that I had my tailpipe removed going over the rearend and now I can tell when it kicks in. It sounds like a manual tranny in a high gear at low speeds but it does work, and through all of the gears.
 

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bytehoven said:
Is there a way to program MDS OFF?
I don't know about a way to program it, but I know they can remove the solenoids. I don't really haul anything with my truck and my drive to work is 12 miles one way and I usually cruise at 55 mph and it stays on for most of the way unless going up a hill or something. I think it's effectiveness all depends on your driving style, terrain in your area and the weight of your load. For me it saves me alot of gas, for other people it may not.
 

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Bytehoven....If you don't want the MDS activated, just drive around in "tow mode," which will over-ride the MDS. Having owned an 03 and now an 07 Hemi Ram, I agree that MDS makes a difference with gas mileage. The best highway mileage I ever got with my 03 was 16 mpg. With my 07....on a trip from SC to DE (560 miles) with a brand new engine with less than 1000 miles on it...and traveling between 75 and 80 mph on I95, I got almost 18 mpg (4x4 QC).
 

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waldershrek said:
I don't know about a way to program it, but I know they can remove the solenoids. I don't really haul anything with my truck and my drive to work is 12 miles one way and I usually cruise at 55 mph and it stays on for most of the way unless going up a hill or something. I think it's effectiveness all depends on your driving style, terrain in your area and the weight of your load. For me it saves me alot of gas, for other people it may not.

Just curious, how do you know for certain when your MDS is engaged. Can you tell the difference in sound with a stock exhaust? Is there some other obvious sign?
 

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MDS is only good for long trips above 50+ MPH. I get horrible gas mileage in the city 10-13MPG....but then on the highway going around 70+ i get 18-20MPG.
 

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50 HP could propel these trucks at steady state cruise at 60 MPH. Yes, it does work. I get 15 MPG around town, a buddy with an '05 gets 12-13 driving like a grandma. If you always have your foot in it, it will never come on. You have to drive like a sane individual for it to kick in, but when it does, you'll save gas.
 

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Discussion Starter #16 (Edited)
DelawareDon said:
Bytehoven....If you don't want the MDS activated, just drive around in "tow mode," which will over-ride the MDS. Having owned an 03 and now an 07 Hemi Ram, I agree that MDS makes a difference with gas mileage. The best highway mileage I ever got with my 03 was 16 mpg. With my 07....on a trip from SC to DE (560 miles) with a brand new engine with less than 1000 miles on it...and traveling between 75 and 80 mph on I95, I got almost 18 mpg (4x4 QC).
18 mpg @ 75 mph with a 4x4? was this towing a boat, with 6 people in the cab driving uphill too?

lpfan4life85 said:
MDS is only good for long trips above 50+ MPH. I get horrible gas mileage in the city 10-13MPG....but then on the highway going around 70+ i get 18-20MPG.
are you in a 2wd?



i get 18 @ 55 when im empty and its not to hilly.

TexasAxMan said:
50 HP could propel these trucks at steady state cruise at 60 MPH. Yes, it does work. I get 15 MPG around town, a buddy with an '05 gets 12-13 driving like a grandma. If you always have your foot in it, it will never come on. You have to drive like a sane individual for it to kick in, but when it does, you'll save gas.
im sure 50 hp could with a power to weight ratio of 1 hp per 100 lbs vs the 20 lbs per hp on a stock 4.7.

the better mileage is propbably from deactivation during idle not the driving itself.

the math just doesn't add up. that truck cant excellerate at 2000rpm with half its cylinders off.

somone be a man and yank 4(or is it 8 because of dual plugs?) plug wires off and trie to drive down the road and get better mileage. ( i would try but i have no pliug wires)
 

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TRICK TURBO
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12many said:
18 mpg @ 75 mph with a 4x4? was this towing a boat, with 6 people in the cab driving uphill too?


are you in a 2wd?



i get 18 @ 55 when im empty and its not to hilly.



im sure 50 hp could with a power to weight ratio of 1 hp per 100 lbs vs the 20 lbs per hp on a stock 4.7.

the better mileage is propbably from deactivation during idle not the driving itself.

the math just doesn't add up. that truck cant excellerate at 2000rpm with half its cylinders off.

somone be a man and yank 4(or is it 8 because of dual plugs?) plug wires off and trie to drive down the road and get better mileage. ( i would try but i have no pliug wires)


It doesnt deactivate during idle and it will not accelerate at 2000 RPM's.. Yank 4 plug wires off and your trucks not gonna start much less getter better mileage..
 

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12many said:
18 mpg @ 75 mph with a 4x4? was this towing a boat, with 6 people in the cab driving uphill too?


are you in a 2wd?

the better mileage is propbably from deactivation during idle not the driving itself.

the math just doesn't add up. that truck cant excellerate at 2000rpm with half its cylinders off.
ok, so you may wanna get the facts straight.

MDS does not come on during idle. There is quite a list of variables which must be met for MDS to kick in. Also, I've got a 4x4 and have gotten up to 23mpg on a 80mile trip.

Around town, I get like 13-15mpg, but on the highway I see a fairly good improvement. Average, for the week, I can get 18mpg which I don't consider too bad for a 6000lb+ truck.
 

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TRICK TURBO
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12many said:
are you agreeing with me or correcting me?
and the plug wire crack was a joke . i think we all new it wouldn't run
guess i should have said it doesnt deactivate 4 cyl at idle.. so yes i was correcting you.. MDS is a huge plus on these trucks for mileage.. With 456's my truck stays in MDS and i see 22 mpg's no problem..
 
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