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  #1  
Old 05-19-2017, 02:14 AM
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MDS deactivation

This aspect may have been discussed before, but could not find answer to my questions. The MDS on my Jeep works very well, but I have some questions. When I fitted a freeflow exhaust system, I had the cats removed. After 140 000km both cats looked in surprising very good condition. However, the exhaust noise and bad drone when MDS is on, made me put the cats back to kill the MDS drone. Could not find a suitable resonator to fit in place of the cats here in South Africa, or maybe the exhaust shop was not up to scratch.
Using software programs like HP Tuners, the MDS can be deactivated. Then I can remove the cats without having the drone noise. So, following questions:
1. What detrimental effect will result over time by not working the MDS components. Becoming "sticky" due to no movement and not working when switching on again.
2. What fuel saving does the MDS actually give on long distance driving.
3. Does the MDS not cause half the engine to wear much more than the other half, resulting in a "sick" half engine over time and that half becoming more breakdown prone?

Your thoughts please.

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Old 05-19-2017, 08:56 AM
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Re: MDS deactivation

The key to eliminating the "MDS drone" is the exhaust system. If your muffler shop can't do it, they are the problem. With my custom headers and 3 in. cat. back, any drone that I have is so minimal that it doesn't bother me or the wife. I do have, in this order, a 12 in. glass pack, a Magnaflow 14589 muffer and finally in the resonator position an Xlerator AP XS1229 muffler. All of these are straight through with no switchbacks of exhaust flow within them.

To answer your questions:
1. There shouldn't be any detriment by rendering the MDS inoperative, especially if you use a good synthetic oil.
2. On my 06 modified Hemi (see signature) turning the MDS off makes a 2-3 mpg difference on the highway. In town there is almost no difference.
3. I don't believe this occurs, but can't prove it. There are many Hemi's with MDS that have gone over 200,000 miles without issue. Again, with my mods., my MDS is active over ~90% of the time during highway driving. Normally, on stock Hemi's I've read that MDS is active somewhere around 30-35% of the time.

This is my experience, but I hope it helps you a bit.
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05 LX/RT & 06 WK/GCO, modded similarly, MDS "ON" Light, Vortex Gens, Debadged, DashHawk, BT Catch Can, SRT CAI W/Add Air Inlet, K&N Filter, Sonnax Trans Press Booster, SC Tuner W/Adv Trans Tuning App, DS Tuner, Cust tube headers w/3 in. catback, Bilsteins, SRT frt/rear bumpers, Eibach SRT Lwr Sprgs & Sways, FRI Sidewinder Cam Adv 2*, 6.1 valvetrain, SLP 25% UD Pulley, BBK 90mm TB, SOS Coils/.060 plug gaps. 20 in. SRT Reps.
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Old 05-19-2017, 09:17 AM
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Re: MDS deactivation

Thanks Jeepcogman. The MDS on my Jeep is also active most time.
Could you post pics of your custom headers with some details. Also what pos and neg effects do you experience. How difficult was it to fit the headers?
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Old 05-19-2017, 07:14 PM
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Re: MDS deactivation

There are no negatives with the operation of the custom headers and exhaust system and the end result is very noticeable. The only problems I've had were the header flange bolts coming loose causing exhaust leaks. I finally broke the code for a lasting fix after I had to remove them for a third time to have some cracks fixed. This time I used Percy's Seal Forever dead soft aluminum gaskets and a better quality bolt with Nord Lock Wedge Washers. Now they'll never leak at the flanges and the bolts will never come loose unless I loosen them.

Two of the times I had the flange leaks I just removed all the bolts and replaced the gaskets. It's fairly difficult to get to all the bolts but, with the right tools, it is doable. The last time (with the cracks) I had to completely remove both sides and it required cutting the head (Y) pipes just in front of the catalytic converters. Then they come right out. After getting them re-welded, it wasn't too much of a problem placing them back where they belong, but getting to some of the bolts was still a problem. Cost to re-weld the head pipes back in place was $20 US.

See pix with the header sitting on the front support for the "after re-weld" and before the reinstall. The other pix are of part of the build and comparisons with the stock log type manifolds and the headers.
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05 LX/RT & 06 WK/GCO, modded similarly, MDS "ON" Light, Vortex Gens, Debadged, DashHawk, BT Catch Can, SRT CAI W/Add Air Inlet, K&N Filter, Sonnax Trans Press Booster, SC Tuner W/Adv Trans Tuning App, DS Tuner, Cust tube headers w/3 in. catback, Bilsteins, SRT frt/rear bumpers, Eibach SRT Lwr Sprgs & Sways, FRI Sidewinder Cam Adv 2*, 6.1 valvetrain, SLP 25% UD Pulley, BBK 90mm TB, SOS Coils/.060 plug gaps. 20 in. SRT Reps.
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Old 05-20-2017, 03:50 AM
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Re: MDS deactivation

Many thanks. Appreciate
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Old 05-20-2017, 04:29 AM
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Re: MDS deactivation

Jeepgcoman, the air intake tube you fitted, is that from a 6.1 SRT? I also want to change the intake tube on mine, but want to keep the standard airfilter and box setup.
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Old 05-20-2017, 06:15 PM
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Re: MDS deactivation

I use a modified LX (Chrysler 300C, Magnum, Charger) SRT8 intake tube and airbox. The LX SRT8 intake tube is shorter than the WK SRT8 one and I had to extend its length by about 3-4 inches for it to get to the LX SRT8 airbox.
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05 LX/RT & 06 WK/GCO, modded similarly, MDS "ON" Light, Vortex Gens, Debadged, DashHawk, BT Catch Can, SRT CAI W/Add Air Inlet, K&N Filter, Sonnax Trans Press Booster, SC Tuner W/Adv Trans Tuning App, DS Tuner, Cust tube headers w/3 in. catback, Bilsteins, SRT frt/rear bumpers, Eibach SRT Lwr Sprgs & Sways, FRI Sidewinder Cam Adv 2*, 6.1 valvetrain, SLP 25% UD Pulley, BBK 90mm TB, SOS Coils/.060 plug gaps. 20 in. SRT Reps.
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