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Author Topic: MDS Sucks  (Read 4395 times)

Offline 04QC4X4

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MDS Sucks
« on: January 02, 2009, 12:44:15 am »
I've had my truck for a little over a month now and I've come to hate the MDS system.  It sucks in town and on the highway.  It kicks in way too early and kills throttle response.  On the highway it kicks in and out constantly and is really annoying.  The kicker is that this truck doesn't get any better mileage than my previous HEMI that didn't have MDS.  I now find myself driving in Tow/Haul mode because it disables the MDS, but it locks out 5th gear so I can't use it on the highway.  I'm considering buying a programmer that can disable MDS, but I hate to spend $400 just to disable MDS.  I really wish the dealer would disable it for me.  Just some info if anyone is considering buying a late model HEMI.

2008 Ram 1500 QuadCab 4X4 Lone Star Edtion
5.7 HEMI, Automatic Transmission
 
2006 VW Jetta TDI (40 mpg)

Offline Parts/Service

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Re: MDS Sucks
« Reply #1 on: January 02, 2009, 01:11:13 am »
I have not found a way to disable the MDS with the StarScan.  But I bet you could un-plug the MDS solenoids and use a resistor in its place to fool the PCM to thinking the solenoid is still plugged up.  Just have to figure out how to not fry the PCM when it tries to activate the MDS...

Offline Cumminalong

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Re: MDS Sucks
« Reply #2 on: January 02, 2009, 04:22:06 am »
Dave, what is the voltage that the MDS solenoids send back through the signal wire to the ECM?

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Re: MDS Sucks
« Reply #3 on: January 02, 2009, 04:34:48 am »
The wiring diagram does not show me the voltage, But i ASSUME it is 5 volts. Gonna have to do more research....

Offline noplugs

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Re: MDS Sucks
« Reply #4 on: January 02, 2009, 04:43:22 am »
I have not found a way to disable the MDS with the StarScan.  But I bet you could un-plug the MDS solenoids and use a resistor in its place to fool the PCM to thinking the solenoid is still plugged up.  Just have to figure out how to not fry the PCM when it tries to activate the MDS...

I think the problem you'll run into is that even though the PCM wouldn't be activating the solenoids is that the PCM will still not inject fuel nor fire the sparkplugs so it will still disable half the cylinders.(or whatever it actually does)
You may have to find a PCM altering way to fix this.
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Re: MDS Sucks
« Reply #5 on: January 02, 2009, 05:06:11 am »
The MDS actually works off of oil pressure, so It is a little difficult to disable...   

The Multiple Displacement System (MDS) provides cylinder deactivation during steady speed, low acceleration and shallow grade climbing conditions to increase fuel economy. Both four and eight cylinder configurations have even firing intervals provide smooth operation. Two cylinders on each bank are active when the engine is in four-cylinder mode – every other cylinder in the firing order. All of the cylinders that are deactivated have unique hydraulic valve lifters that collapse when deactivated to prevent the valves from opening. Engine oil pressure is used to activate and deactivate the valves. It is delivered through special oil passages drilled into the cylinder block. Solenoid valves control the flow. When activated, pressurized oil pushes a latching pin on each valve lifter, which then becomes a “lost motion” link. Its base follows the camshaft, but its top remains stationary, held in place against the pushrod by light spring pressure but unable to move because of the much higher force of the valve spring.



NOTE:  It is critical to use the recommended oil viscosity in 5.7L engines that use MDS. 

Deactivation occurs during the compression stroke of each cylinder, after air and fuel enter the cylinder. Ignition then occurs, but the combustion products remain trapped in the cylinder under high pressure, because the valves no longer open. No air enters or leaves. During subsequent piston strokes, this high-pressure gas is repeatedly compressed and expanded like an air spring, but fuel is not injected.


Offline i11m10c2

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Re: MDS Sucks
« Reply #6 on: January 03, 2009, 08:54:48 am »
Thats why the other truck we bought (08 1500) we asked for the new 4.7 v8 we had mds on the jeep and it was anoying as hell always ticking shaking and the throttle response was terrible. and the new 4.7 is a regular pushrod v8 with no crap all over it and the hemi was only 30 hp more

hey couldnt you get a ecm from a non MDS hemi and install in place of the other one ?

Offline 04QC4X4

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Re: MDS Sucks
« Reply #7 on: January 03, 2009, 06:21:07 pm »
Thanks for the info.  I've been reading on other forums and I don't think anyone has found a way to disable it besides using a programmer.  I'm going to keep my eyes open.  I probably would have gotten a 4.7 if I had know the MDS was this annoying though.
2008 Ram 1500 QuadCab 4X4 Lone Star Edtion
5.7 HEMI, Automatic Transmission
 
2006 VW Jetta TDI (40 mpg)

Offline Woligator

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Re: MDS Sucks
« Reply #8 on: January 07, 2009, 02:21:37 pm »
does my 05 5.7 have that mds ????

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Re: MDS Sucks
« Reply #9 on: January 08, 2009, 03:08:57 am »
does my 05 5.7 have that mds ????

Being a 2005, I don't think yours has the MDS Woli...

Offline Woligator

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Re: MDS Sucks
« Reply #10 on: January 09, 2009, 03:17:34 am »
does my 05 5.7 have that mds ????

Being a 2005, I don't think yours has the MDS Woli...

anything else that might suck on that truck???

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Re: MDS Sucks
« Reply #11 on: January 09, 2009, 03:32:05 am »
does my 05 5.7 have that mds ????

Being a 2005, I don't think yours has the MDS Woli...

anything else that might suck on that truck???


The only thing that sucks on a Hemi truck is the fuel mileage.

Offline 04QC4X4

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Re: MDS Sucks
« Reply #12 on: January 12, 2009, 01:32:46 am »
I agree.  Besides the fuel mileage they are great engines.
2008 Ram 1500 QuadCab 4X4 Lone Star Edtion
5.7 HEMI, Automatic Transmission
 
2006 VW Jetta TDI (40 mpg)

 

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