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  #13  
Old 01-08-2011, 08:36 PM
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Re: MDS Enable/Disable custom switch?

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Originally Posted by Blutarsky View Post
I've read about the custom led indicator to show when MDS is engaged and wondering if there would be a chance to build a custom switch to enable or disable MDS on the fly, without having to use tools such as Diablo or Superchips.

On my GC 5.7 HEMI - MY2007.

Any idea?
Has anyone done a custom led indicator on their jeep to show if its engaged? if so how did they do it?
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  #14  
Old 01-08-2011, 09:13 PM
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Re: MDS Enable/Disable custom switch?

Yes, I have. I first did this on my LX back in 05. The wiring pin outs are the same and it is actually easier on the WK. There is a grommet in the firewall right behind the PCM where you can easily route the wire into the cabin behind the glove box. Put a Radio Shack LED where you want it and connect it up. Here's the instructions I did back then for the LX. Go back to the beginning of the thread:

http://www.lxforums.com/board/showth...5813#post55813

You can see where I mounted mine in Post #4 of the following thread.

http://jeepgarage.org/showthread.php?t=7566
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Old 01-08-2011, 11:48 PM
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Re: MDS Enable/Disable custom switch?

Mine says when it's engaged in the evic. It says fuel saver over the mpgs.
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  #16  
Old 01-11-2011, 11:43 AM
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Re: MDS Enable/Disable custom switch?

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Originally Posted by jeepgcoman View Post
Regarding the jerking/bucking, I used to have the most problem with everything happening at once while cruising between 60-70 mph. There are a few spots (RPM/speed/incline, etc.) where the transmission would hunt between 4th and 5th gear. This would cause havoc with the MDS and the converter lockup clutch. They would activate/deactivate in response to the continual gear changes.
I have something similar to this between 50-60 mph - if accelerating gradually, when I hit this range I start feeling a shuddering/ vibration. If I give it more gas, it goes away. Not sure if this is the point it is trying to engage MDS or not or if I have a unique issue. I will add that I had a new tranny put in after only a few hundred miles of service due to a faulty fluid pump in the tranny.
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  #17  
Old 01-12-2011, 06:36 AM
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Re: MDS Enable/Disable custom switch?

jeepgcoman, I have read again your GREAT-GREAT explanations!

Summarizing it up, I would say that jerking critical factors are MDS &
Converter Lockup.

In my case I can only feel the jerking when:
- in gear 5, never below
- speed range between 44 - 74 mph
- slightly uphill road, a condition where power required is slightly more than on a plane road

So, I will certainly go for an oil change. If this won't solve the problem (I bet 99% it won't), I will think about the superchips on (verifying Euro-models issue).

How can I test if the converter lockup is involved in the jerking?

Your thoughts appreciated
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Old 01-13-2011, 08:52 AM
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Re: MDS Enable/Disable custom switch?

jeepgcoman, while I understand it would be impossible to leave force 4cyl mode "always on", could it be possible to have a switch enable/disable MDS (back to the original question)?

You didn't comment on this.

I know you can disable it with Diablo & Superchips, however a switch that will enable (default MDS behaviour) and disable (MDS turned off) would be great.

A simple "electric cable" solution that will fool the computer to believe that one of those "no-MDS" conditions is active while it is not.
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  #19  
Old 01-15-2011, 08:45 PM
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Re: MDS Enable/Disable custom switch?

Since the tuners are capable of disabling the MDS, I have not even looked into it. My guess is that since it is controlled through the PCM, it would be difficult to install a simple on/off switch. I suppose you could install a 4 pole switch to the trigger leads of the MDS solenoids, but it may cause a MIL to illuminate. I would still recommend the tuner route.

I just got back from an 800+ mile "vacation" and was able to monitor MDS operations more closely using my DashHawk. I even set up a screen just for MDS parameters....engine load (one of the main ones), absolute throttle position, engine vacuum, engine coolant temp. (may change this one), barometric pressure, and MAP sensor pressure. I know there are other variables involved, but these were the first to come to mind while on the road.

Anyway, on mine at speeds between 55-70 mph (in both 4th or 5 gear), the MDS comes on at 27-29% or lower engine load, with the throttle position at or below about 22%. It kicks off religiously at 31% load. This is really a very narrow window. When in MDS mode, the converter IS NOT locked up. The RPM difference between the converter speed and engine RPM is less than 100 RPM (usually 50-75 RPM) while cruising. As soon as the MDS kicks off (I currently have the Diablosport Tuner installed with the 91 octane tune installed.) the converter almost immediately (maybe 1-3 seconds) goes into lockup. The engine RPM changes (lowers) to meet the converter RPM and they are usually within ~3-5 RPM of each other. As I said earlier, there are some speed/RPM/highway incline, etc. conditions that can (and does on mine) cause the MDS/converter lockup up clutch to cycle repeatedly in fairly quick succession. When that happens I just change speed slightly or backshift it to 4th gear for awhile. The way you are describing your issues sounds like this is what is happening to you. It really causes considerable bucking and jerking as it cycles on and off. Any slight change in incline, wind conditions, (and I even discovered road surface), and many other factors can make the engine load change a few %age points. If you're operating in and around the 27-32% load range, your MDS will hunt. What is the altitude where you are located? On my trip I operated at altitudes from 2400-7000 ft. elevation. I never encountered the hunting this time, but there were many times when the engine load was just above the MDS "trigger" point. I remember thinking that an extra 10-20 hp would probably have the MDS working at those points.

Some of this was discussed earlier, but the way you can eliminate the converter lock and MDS is by going to the Tow/Haul mode. This eliminates both of those functions. If you just want to eliminate the MDS, shift to 5th (if you have it) or 4th if you don't. This will eliminate the MDS only, but the converter lock up will still work. You should be able to isolate the converter lock up operation this way and get a feel for how/when it works and what it feels like.
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  #20  
Old 01-16-2011, 07:34 AM
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Re: MDS Enable/Disable custom switch?

You're making this as the most valuable thread about MDS!! A sort of MDS Academy!

Quote:
Originally Posted by jeepgcoman View Post
The way you are describing your issues sounds like this is what is happening to you. It really causes considerable bucking and jerking as it cycles on and off.
Correct. It does

Quote:
What is the altitude where you are located?
Say at sea level

Quote:
If you just want to eliminate the MDS, shift to 5th (if you have it) or 4th if you don't. This will eliminate the MDS only, but the converter lock up will still work. You should be able to isolate the converter lock up operation this way and get a feel for how/when it works and what it feels like.
Great!! That goes back to a previous thought, once I asked if shifting to "5" would disable MDS or not, beacause in that condition I still had the feeling something was still jerking. This needs a thorough testing!

More to come!
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  #21  
Old 01-16-2011, 03:26 PM
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Re: MDS Enable/Disable custom switch?

More "feelings" after your thoughts.

Drived a bit today:

- Seems road surface has a BIG impact on this feeling. BTW it seems that road surface in a particular speed range can be nasty.

- Could it also depend on tyres wearing, as mine are quite weared?

- Another behaviour I have noticed, if the car hits a stiff "bump" (ie: within long bridges) the engine has a sort of very short choke.
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Old 01-16-2011, 05:05 PM
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Re: MDS Enable/Disable custom switch?

You're right that tire condition can have a big impact on rolling resistance, as will tire pressure, alignment and a host of other conditions. In my unscientific tinkering on my little trip, at times I noticed a 2-3% change in engine load when transitioning from a medium coarse asphalt to a relatively smooth concrete road surface, or vice versa.

Your "bump" needs to be explained more clearly as to circumstances that cause it. Are you describing an engine flat spot (hesitation)? Is cruise control on when this occurs? At what speed does this occur? Does it do it all the time under these circumstances? Kind of weather? Kind of road surface? How worn are your tires? What kind of pressure are you running in them? Anything else you can think of that could cause or aggrevate this condition?
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  #23  
Old 01-17-2011, 11:08 AM
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Re: MDS Enable/Disable custom switch?

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Originally Posted by jeepgcoman View Post
Your "bump" needs to be explained more clearly as to circumstances that cause it. Are you describing an engine flat spot (hesitation)?
Yes, very quick, very short. Could it be there's a sort of engine's "allowed fluctation", by design (I mean the whole engine block, due to shocks the engine could suffer from when offroading? In this case, if the whole engine "fluctuates" a bit maybe something happens in the transmission? Who knows, but I'm probably OT here!

Quote:
At what speed does this occur? Does it do it all the time under these circumstances?
No. But I need further investigation. I adore the scientific approach of you to this problem! I'll stretch the test and post back results
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