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Maximizing MPG with MDS


Tips from the Chrysler Group on Getting the Most Fuel Savings with its Multi-Displacement System

Chrysler Group MDS improves fuel economy up to 20 percent
Standard equipment on almost all HEMI 5.7L engines


Auburn Hills, Mich., Sep 1, 2005 -
Just a few simple tips can help owners of Chrysler Group engines with Multi-Displacement System (MDS) get the most fuel mileage possible from their 5.7L HEMI® V8 engine.

The customer does not need to drive in a certain way to realize a fuel economy improvement with MDS, but these driving habits can maximize their fuel savings with this technology.

Keeping speeds to 65 mph or below – MDS uses four cylinder mode most at these speeds
Use cruise control – this helps maintain a steady speed, generally allowing the HEMI to run on four cylinders for longer periods
Accelerate more gradually – the HEMI will provide V8 power whenever it is requested by the driver
Use a steady throttle whenever possible – this maximizes four cylinder mode
The Chrysler Group MDS is standard equipment with the 5.7L HEMI on seven vehicles: the Chrysler 300C, Dodge Charger R/T, Durango, Magnum R/T, Ram 1500 and Jeep Grand Cherokee and Commander.

With the addition of MDS to HEMI-equipped Dodge Durango and Ram, MDS-equipped vehicles through the end of the 2007 model year will save more than 60 million gallons of fuel each year.

The Chrysler Group MDS seamlessly alternates between smooth, high-fuel-economy four-cylinder mode when less power is needed, and V-8 mode when more power from the 5.7L HEMI engine is in demand. This optimizes fuel economy when V-8 power is not required, without sacrificing vehicle performance or capability.

Chrysler Group was the first to offer modern, large-volume vehicles in North America with cylinder deactivation - the HEMI-powered 2005 Chrysler 300C and Dodge Magnum R/T went on sale in the of spring 2004 with the Chrysler Group Multi-Displacement System, or MDS. Chrysler Group was also the first to offer cylinder deactivation in an SUV with the introduction of MDS in the 2005 HEMI-powered Jeep® Grand Cherokee. Chrysler Group is the first to offer MDS in a pickup truck - the 2006 Dodge Ram 1500.

MDS is a fuel-saving technology that is here today - customers get the power and capability of the HEMI V-8 that they desire with the fuel economy of a less powerful engine.

Rambit
 

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Yes this works!

Add you MDS LED for even more fun. I am not a fan for giving donations to Shell, Exxon, BP, etc.
 

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Use a steady throttle whenever possible – this maximizes four cylinder mode
I often watch my EVIC mpg when driving on the freeway and a steady/constant throttle clearly has the biggest effect on mpg. But being an aggressive driver, I am always modulating my gas pedal as I follow the car in front of me, and then accelerate when I pass them. Driving with a "steady throttle" is just not possible.

Accelerate more gradually – the HEMI will provide V8 power whenever it is requested by the driver
I don't think this saves much gas. Any acceleration immediately puts us in V8 mode. Once in V8 mode, gas savings between slow and fast acceleration is probably small.

Keeping speeds to 65 mph or below – MDS uses four cylinder mode most at these speeds
This graph shows MDS works above 80mph. Not to argue with the Chrysler gurus, but I think it is just easier to keep a steady throttle at lower speeds (65 at below) then it is at higher speeds (70mph and higher). If I cruise at 80mph with a steady throttle, my EVIC mpg will be around 24 to 25. At 60mpg my EVIC mpg is around the same, 24 to 25mpg. But I havn't had chance to verify this because I don't get out on long hauls enough to test it precisely.
 

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I took my C in to have a scan completed to see if my MDS was functioning as I had my battery disconnected a few months ago for some reason and I kept reading where it could disable the MDS. They put my car through a complete scan and downloaded anything new but could not tell me if my MDS had been disabled.

I think it is time to do something with that mod for the LED light to let a person know if MDS is activated under normal driving.
 

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The steady throttle is key here, less so speed above 65. Try the cruise control on a long trip. It is the smoothest one I've ever had and I got a legit 24 mpg on a 1000 mile trip involving 20% local driving, 40% country roads and 40% interstate.
 

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cmego said:
The steady throttle is key here, less so speed above 65. Try the cruise control on a long trip. It is the smoothest one I've ever had and I got a legit 24 mpg on a 1000 mile trip involving 20% local driving, 40% country roads and 40% interstate.
I agree fully with what you say but it would be nice to know in stop and go traffic if the MDS is fully functional and by adjusting your driving to the LED light it should save on gas, and yes if you want the power then it is there.
 

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It would be nice if it kicked in at idle too. I think that would help with stop and go traffic as well.
 

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I wouldn't put the LED for the MDS in the dash....it would be too distractive. Put it lower where it won't distract as much. Mine is just below the ignition switch and is an illuminated rocker switch. I can turn it off if I want, and it is plenty visible between the steering wheel spokes, especially at night. I am the one that did this mod. and posted a "how to" over on the LX forum. I've used the light now for about 6 months and it definitely can help improve mileage once you learn the how/when conditions that turn it on. In town I can coax it to come on when it normally would not be on....but you need the light to be able to see when it activates. Sometimes, at speeds when it should be on and is not, you can turn it on by slightly goosing the throttle and let it coast down a little to turn it on. Most the time it will stay on if in the proper speed range. Also you must know what speed ranges are "dead spots". Generally (on my car) they are around the shift points which are about 28-32, 38-42 for activation only. i.e. Once activated at speeds above those indicated, the MDS will stay on coasting down to about 30 and 40 respectively. The most annoying for me is the 28-32 dead spot. This is the speed that are driven the most here in town. Also, in town, if you have long stretches/light traffic, use the cruise. Here in my town most major intersections are a mile apart and it is easy to "drive with the cruise". Also, bear in mind, that the selector must be in "D" for the MDS to work. Above about 50 mph, the MDS is very predictable and will activate/stay on maybe 85% of the time as long as you're fairly level, with light load on engine. Again, cruise control is the key....let the PCM manage everything.
There are several other forum members here that have done the mod. Let's here from them on some hints, shortcuts on install, etc. Still, the best way to improve mileage is to slow down and NOT stick the foot in it as much. I know that is tough (I still do it from time to time), but my in town mileage runs 15-18, and on the road is almost always 25-30. My best mileages on the road....29.8 and 30.3 were both attained using 87 octane gas and 6-7 oz. of acetone. Both were also at elevation (4500-7000 ft.) at speeds between 60-65 mph. Other things that seem to help me are tire pressure....40 PSI in fronts, and 36 PSI in the rears; add the additional 3 in. duct from the front of the airbox to behind the grill, and a low restriction filter. I also have a double wall, triple insulated CAI which also helps slightly. See my mileage tests/observations (3500 miles worth) with all my different configurations in the following and referenced threads: http://www.300cforums.com/forums/showthread.php?t=9732

One final thought. I didn't by this thing for mileage, either, but DCX put the MDS in there for a reason.....save gas. IMO, we have the best of both worlds, power when we need/want it and economy (for a vehicle this size) when we need/want it. Gas today (87) is now up to $2.97/gal. Why not maximize the use of the MDS, unless you have money to burn?
 

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Great reply as usual Magnumman! I love the MDS light and you are correct about goosing the throttle then backing off, it works most of the time. I was able to increase mileage somewhat by acceleratinng moderately agressivly then backing off at a little above 40 to get the MDS engaged. I however, cant seem to get the in-town ,mileage above 13-13.7 MPG. I have a little less than 5M miles so it may imrove, hopefully ,as 85% of my driving is in-town! I will try the 40 psi front and 36 rear pressure, I just recently added 5psi from the recommended 30psi and havent seen improvement yet. Does the mileage really suffer using 87 octane without acetone?

Thanks
 

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Re. Tips from the Chrysler Group on Getting the Most Fuel Savings with MDS

Rambit said:
Maximizing MPG with MDS
Tips from the Chrysler Group on Getting the Most Fuel Savings with its Multi-Displacement System

Chrysler Group MDS improves fuel economy up to 20 percent
Standard equipment on almost all HEMI 5.7L engines
Great posts, all.

Bottom line: If you're driving outside of basic pre-defined and immutable MDS parameters, all the super-mojo MDS technique in the world won't help.

Here are some numbers from previous posts here & other forums:

1. Effective speed range: 25-83 mph. (Anyone with an MDS light out there care to confirm or amplify?)
2. Required tranny selection: Drive, and only drive. Not 4, 3, or any of the other numbers that may show up on your gear selection indicator.
 

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Csteve300,
I think you've got it with the MDS, and yes, your mileage should improve with more miles on your "C". I've got over 12,000 now, and it seems that the mileage improved more after the so called magic 7000 mile mark. I can't really say that's true though, for sure. All I know is that is has gotten better with more miles. As for the acetone...I am at 2800 ft. elevation which is no problem for 87. At higher altitudes I've even run 85 and got my second best mileage (29.8) with it, and six oz. of acetone. I think at lower elevations you can get away with it, but your mileage will probably suffer as the PCM retards the timing. Example: My best tank on my first 1500 mile trip was 446 miles on 16 gallons of 87 with 7 oz. of acetone. Same tank first leg at 4500 ft. got 30.3 over 178 miles. Last leg, same tank at 200-1800 ft., 161 miles, I only got 25.3...BIG DIFF. All I can say is try it and see what happens. In town I really don't see much diff. using acetone. Also, if you can, try to use cruise in town if possible, and if you don't have a low restriction filter, try it, and maybe the 3 in. duct added to the front of the airbox....unless you already have a CAI. I just did the spark plug wire mod. and am doing my first mileage check. We'll see if anything changes. 87 is now $2.97/ gal. here.
 

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Meister,
On mine, about 20-28, 32-38, and above 42 works. Those mph's in between are the approximate shift points (29-31 and 39-41). The highest my MDS has worked is about 82 mph. The low numbers are coast down. Generally, you have to get toward the middle/top of those ranges to get it to come on though. Ocassionally, it will come on in a narrow range16-19, but so seldom I can't figure out how to get it to come/stay on. Basically, above 45 or so it's very predictable and will be active most of the time, if you're within the parameters, and have the cruise on.

For the MDS to work, the selector MUST be in "D". When it's on, as soon as you downshift out of "D" it will kick the MDS out.
 

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magnuman said:
Meister,
On mine, about 20-28, 32-38, and above 42 works. Those mph's in between are the approximate shift points (29-31 and 39-41). The highest my MDS has worked is about 82 mph. The low numbers are coast down. Generally, you have to get toward the middle/top of those ranges to get it to come on though. Ocassionally, it will come on in a narrow range16-19, but so seldom I can't figure out how to get it to come/stay on. Basically, above 45 or so it's very predictable and will be active most of the time, if you're within the parameters, and have the cruise on...
magnumman, thanks for the amplification of the low end numbers and verification of the high end number. Cruise control set at 82mph, or 81mph for increased liklihood of engaging, appears to be our fastest "econo" cruise setting. That's what I've been using since end of break in, but can only stand it for so long until I have to let her run a bit.
 

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no high tire pressures here

If i run over 30 psi my 300 hits the bumps hard, i'm keeping my pressure at 30 psi as reccommended. My best milage has been 26 mpg with the a/c running.
This was at 69 mph indicated. Why the fingernail polish remover acetone?
 

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Jimmy said:
If i run over 30 psi my 300 hits the bumps hard, i'm keeping my pressure at 30 psi as reccommended. My best milage has been 26 mpg with the a/c running.
This was at 69 mph indicated. Why the fingernail polish remover acetone?
You're right, Jimmy. The ride will be harder and noisier, but the handling and tire wear will be better. At 30 PSI, you'll probably start noticing excessive feathering on the outer edges of the tires, maybe a little squealing in the corners, and shorter tire life.....but your ride will be softer and quieter.
 

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You're right, Jimmy. The ride will be harder and noisier, but the handling and tire wear will be better. At 30 PSI, you'll probably start noticing excessive feathering on the outer edges of the tires, maybe a little squealing in the corners, and shorter tire life.....but your ride will be softer and quieter.
I have never achieved more than about 20 MPG at 80 MPH on cruise control on smooth roads in my 300C. Wish I could!
 

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This graph shows MDS works above 80mph. Not to argue with the Chrysler gurus, but I think it is just easier to keep a steady throttle at lower speeds (65 at below) then it is at higher speeds (70mph and higher). If I cruise at 80mph with a steady throttle, my EVIC mpg will be around 24 to 25. At 60mpg my EVIC mpg is around the same, 24 to 25mpg. But I havn't had chance to verify this because I don't get out on long hauls enough to test it precisely.
That's strange, because I have noticed the contrary. On a 350-mile highway trip, I kept a close eye on the fuel economy. I set the cruise control at various speeds to observe the effect on MPG, and would reset the MPG each time I made a change in speed. At speeds just under 80mph, the EVIC would indicate 22-23MPG. Once I got over 80mph, the MPG would drop to 19-20MPG. This was a pretty significant change, and able to be duplicated as I tried it both ways a couple of times.

This was on I57 in Illinois, which is pretty flat and doesn't have many curves. I was heading south during the winter and I don't recall how much wind resistance I was fighting. Based on what I was observing, it would seem to suggest that the MDS was not operating much if at all above 80mph.
 

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You're right, Jimmy. The ride will be harder and noisier, but the handling and tire wear will be better. At 30 PSI, you'll probably start noticing excessive feathering on the outer edges of the tires, maybe a little squealing in the corners, and shorter tire life.....but your ride will be softer and quieter.
Actually, handling and tire wear generally decrease if you increase the tire pressure too much. For optimal handling, depending on conditions, you'll want to have 30-33psi in the tires. (This comes from autocross and roadracing experience.) Going a bit higher than that will improve wear patterns and gas mileage. Going significantly higher will only improve mileage but may cause excessive tire wear on the center of the tread and will compromise ride comfort. (Ever look at the charts in auto parts stores that try to help you diagnose suspension problems by looking at tire wear? Too much pressure wears the center, and too little wears the outside edges.)

Man, if only bumping up the tire pressure helped mileage, handling and wear. That would be just plain awesome!
 
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