New Dodge Engine
New User
Joined: Jan 2006
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if you remember lincoln had that in the early 70s but they couldnt get the bugs out. all they do is shut down 4 cylinders and retards the timing for improved gas mileage. the viper has been running on 8 cylinders exept when hit hard since 94 its smart to do. its all about the computer and emission controls. hot rod mag had a chevrolet corvette called the greenslime last year the guy spent 15000.00 on the computer set up the car goes 227mph and gets 27mpg if he can doit why cant we.
Elder User
Joined: Nov 2002
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From: Norwood USA
The Viper always runs on 10 cylinders, its never had the cylinder deactivation. The commercial you saw was for the MDS system. Like Shane said, it shuts down 4 of the 8 cylinders during cruising speeds to help save gas. It was used by mercedes for awhile, and when the 300C was introduced with the HEMI, they introduced it on that vehicle. Its a tried and true system that doesn't have any bugs, and works well on the cars. I doubt you'll see much difference on the truck due to the fact that the only time it will shut the cylinders down will be on a flat surface when the motor really doesn't need to do much work.
Elder User
Joined: Feb 2004
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From: Orange
Whoopy-doo. My 2000 Grand Marquis got 29.3 mpgs on the highway with the cruise control set at 65. All it took was a swap to 2.73 rear gears.
Stop playing with shutting the engine off garbage. The new tahoe was tested by Car and Driver and they got an observed...12 mpgs. Yeah, 12. MDS doesn't work that noticeably to the everyday driver.
If manufacturers want better highway mileage, just do what Chevy has already been doing with the Vette--give it a double overdrive. No, performance-wise the Vette doesn't need a 6th gear. It hits top speed in 5th, not 6th. The 6th gear is it's gas mileage gear. Manufacturers should just put gear vendors behind their transmissions and call it a day.
Stop playing with shutting the engine off garbage. The new tahoe was tested by Car and Driver and they got an observed...12 mpgs. Yeah, 12. MDS doesn't work that noticeably to the everyday driver.
If manufacturers want better highway mileage, just do what Chevy has already been doing with the Vette--give it a double overdrive. No, performance-wise the Vette doesn't need a 6th gear. It hits top speed in 5th, not 6th. The 6th gear is it's gas mileage gear. Manufacturers should just put gear vendors behind their transmissions and call it a day.
Posting Guru
Joined: Jun 1999
Posts: 2,404
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From: Everett, Wa
Of course if you jack up the HP on the Vette you can use 6th to go even faster. I think calculated the vette is capable like 306 if you could take 6th to 6500 rpms. Probably need 1000 hp at the rear wheels to do that though.
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New User
Joined: Sep 2005
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Where are the benefits?
The un-even wear was my concern as well. By the way, I saw that commercial again today, and the MPG with the MDS system is only 14 city / 18 highway. Where are the benefits there?
Senior User
Joined: Jan 2004
Posts: 184
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The wear factor is not an issue. The MDS system closes both intake and exhaust valves resulting in the off cylinders retaining the gases and acting like a spring. This is very important for both wear and ring tension.
Mileage varies, the quoted 14 - 18 is for pickups. The MDS cars owers have documented up to 29 mpg hwy and for the most part, average 18 in mixed driving. Many can get the suggested 25 mpg, however, fuel economy is very subjective as it really depends on how one drives. Some get lower, some get higher.
Mileage varies, the quoted 14 - 18 is for pickups. The MDS cars owers have documented up to 29 mpg hwy and for the most part, average 18 in mixed driving. Many can get the suggested 25 mpg, however, fuel economy is very subjective as it really depends on how one drives. Some get lower, some get higher.
Posting Guru
Joined: Jul 2001
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Displacement on Demand is not new to Dodge. All Hemi engines for 2006 and certain 2005 Hemis have it as well. Most folks don't even know they have it. Like it or not, it is the future for HP and fuel mileage.
Elder User
Joined: Oct 2004
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Originally Posted by FRECSF
The wear factor is not an issue. The MDS system closes both intake and exhaust valves resulting in the off cylinders retaining the gases and acting like a spring. This is very important for both wear and ring tension.
What I don't understand is that in these days with variable valve timing and variable fuel injection, why don't manufacturers build ECU's with TWO modes: economy and performance?
Senior User
Joined: Jul 2004
Posts: 376
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with both intake and exhaust valves closed and air acting like a spring....I would think that it takes SOME horsepower to continually recompress those cylinders....even though theoretically you might get something from the "spring".....nothing is 100% efficient