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Chrysler Puts MDS HEMI in New Ram Pickup; Estimates Up to 20% Better Fuel Economy


Chrysler has introduced the new 2006 Dodge Ram 1500, featuring the first implementation of a cylinder deactivation system in a pickup truck. The company estimates that the Ram 1500 equipped with a HEMI engine and Chrysler’s Multi Displacement System will provide up to a 20% improvement in fuel economy over a non-MDS system. (Earlier post.)

The Ram’s 5.7-liter HEMI V-8 delivers 345 hp (257 kW) of power and 375 lb-ft (508 Nm) of torque. The MDS transitions the engine from eight cylinders to four in 40 milliseconds (0.040 seconds) under certain driving conditions.


The RAM 1500 also offers a 4.7-liter V-8 and 3.7-liter V-6 engine. Because of MDS, the 5.7-liter HEMI delivers 46.8% more power than the 18% smaller 4.7-liter V8, it does so with only a 2% penalty in fuel economy. (Chart at right, Click to enlarge.)

That said, and as we noted in the earlier discussion of the Chrysler 300 with MDS, the Ram is still a big, heavy vehicle that consumes a lot of fuel. Fuel economy (combined) for the HEMI version is 15.6 miles per gallon US. Fuel economy for the 4.7-liter V-8 is 15.9 miles per gallon.

2005 Dodge Ram 1500
3.7-L4.7-L5.7-L w/MDS
Power215 hp (160 kW)235 hp (175 kW)345 hp (257 kW)
Torque235 lb-ft (319 Nm)300 lb-ft (407 Nm)375 lb-ft (508 Nm)
Miles/Gallon (2wd)17.915.915.6
L/100km (2wd)13.114.815

Chrysler Group’s MDS-equipped lineup also includes the HEMI-powered Chrysler 300C, Jeep Grand Cherokee, Dodge Charger, Dodge Magnum and Dodge Durango, with the all-new 2007 Jeep Commander arriving in showrooms this fall. By 2007, Chrysler Group will have nearly 1 million vehicles on the road with MDS.

The company’s approach with MDS is comparable to the approach GM has said it will take with hybrid powertrains—implement them on the high-power, high-volume vehicles first.

But with MDS, as with hybrid powertrains, both companies need to apply their technologies to enable engine downsizing, and significant increases in fuel economy, instead of applying the technology to increase power, while maintaining fuel consumption.



MDS reduces throttling losses at cruise, but does not affect internal friction nor idling losses of the bigger engine.  It was a good idea and right up to date... two decades ago, with the V8-6-4.

If DC wanted to make a bigger difference they could go with something like a turbocharged Otto-Atkinson cycle.  Variable compression reduces knocking problems, while turbocharging increases power available from a smaller engine.  If variable intake valve timing is used to cut throttling losses and achieve greater expansion than compression ratios, the economy jump could be considerable.  Another 20% over the 3.7 liter?  I don't know, but I wouldn't rule it out.


The prior attempt at MDS by GM was a resounding failure, as any dealership mechanic that worked when they were out can verify (like myself)No such problems with the MDS Hemi exsist.
In 1981, engineers at Cadillac made an attempt at producing better gas mileage for its line of heavy luxo-liners. Dubbed the V8-6-4 (or, Displacement On Demand), the engine changed cylinder modes, eliminating two cylinders at a time as power demands decreased. The idea was right on the money, but the available technology to implement it was not. Measuring 368 cubic inches, oil pressure to specially-designed hydraulic lifters was shut off by solenoids, which caused the lifter to collapse, and effectively prevented the cam lobe from opening the related valve. The biggest rap with the V8-6-4 was a distinct hesitation when cylinders were deactivated, which commonly became known as a "driveability" problem."

Robert Newton

I have a 2006 Ram 1500 with the Hemi engine with MDS. I find that it works great out on the road but around town it is terrible. It constantly is cutting in and out and I think they should not allow it to cut in until fifty or sixty miles per hour. All of the dealers that I have been in touch with say that they cannot do anything about it.


I'm wanting to buy a 2007 Ram hemi with the MDS. But I'm just a little unfamiliar with this new system they put in the trucks. Does anyone know if they would have alot of computer error and leave you stranded? Or if it fails does it just stay in V8 form?


I have a 2007 Ram 1500 4X4 with Hemi/MDS. I agree with the top writer; it should Deactivate cylinders at higher RPM/Speed. Mine actually will go to 4 mode in 1st gear now, and as low as 850 RPM. Don't think anyone yet has figured out how to make an 8 cylinder engine run smooth on 4 at that shakes and dealer says no relief; not enought pepole have complained for Chrysler to offer a fix. I thought about a performance chip, but mfg's rep discouraged any hope for success. I know for a fact I am not the only one having this situation. It may cause me to dump it!


My 06 ram 1500 quad 5.7 with the mds gets 11-13 mpg on the freeway! I get 10.5 mpg pulling a trailer thru the mountains. The dealer says this is normal for a hemi. It has 13,000 miles so it is broken in. If they adverstise that the mds will get 20% better mileage then why is it only getting 12 mpg. the dealer keeps giving me the run around. anyone have same situation or suggestions?


Can you retro-fit this MDS system to my 2003 5.7 Hemi?
Although after reading the above comments, maybe I should leave well alone!
Anyone found any good fuel saving tweaks for this very impressive but very thirsty lump?


I agree with the statements made above. I got the 2008 chrysler SRT Design w/ 5.7 mds and I hate when it goes to 4 cylinders in first gear because it makes this terrible 4 cyl exhaust leak ticking sound. The only thing I have used to not here the sound is put the car in auto stick where mds is deactivated. I can't believe the chrysler dealers and manufactures act like this isn't something they should resolve. I may be getting rid of this car very soon just because of the MDS.

you suck

mds rules


my 2007 Dodge Ram with mds does the same thing , shuts down to 4 when driving slow , HaHa Ha Gas mileage what a joke my 2005 dodge ram without mds was alot better on fuel . Drive the truck at 60 mph or 160 mph still get 10.5 mile to the gallon . If dodge does not do somthing better with their 2009 model it may be my last of a long line of dodges .


i have an 06 ram w/mds and i take of slow in the city to let the mds kick in so i save gas. dont care if the people behind me get mad from going slow. get about 16 mpg in city. if you get mad from mds in the city then turn overdrive off and it prevents mds turning on


I have an 06 MDS Hemi and am getting 16.7 running around no highway driving. Very happy with it. It IS all in how you drive it though. 345 HP is tempting at times.


I cant find any where does the MDS switch in at idle, i.e. stoped at light? I would hope so, but have found no reference wether it does.

Just like the j. wrght said, in town shut the overdrive off and there is no more MDS vibration or noise, easy, easy fix.

slang blade4

I taked off in my dodj rel slow an save gas 1 tim.

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