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Discussion Starter · #1 ·
When I'm cruising with cruise control on and start up a heal I can feel a small jerk and hear it happen in the exhaust. I'm assuming this is when MDS is kicking in the extra cylinders. Do others experience this? Is it normal or should I get it checked out?

Thanks
 

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or, its possible that you just ran over a squirrel...
 

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but yes its normal.

when i had the car 'stock' i never noticed any change. i thought maybe it was make believe.

but after the longtube headers and the borla, i can definitely feel & hear every transition.

its normal.
 

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Discussion Starter · #4 ·
LOL - Nope, no squirrel killing!
 

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no i dont think thats normal. if you have a stock exhaust you shouldnt even be able to hear the difference over the road noise. sometimes i can hear it but i have the daytona exhaust, sometimes i cant hear it. you def. shouldnt be able to feel it though.
 

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Discussion Starter · #6 ·
I never noticed it till I did the brylcreem mod.
 

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Never heard it until I got the Zoomers, and the Superchips.

Before Zoomers & Superchips >> Nothing

After Superchips >> A slight 'jerk'...nothing major

After Superchips & Zoomers >> Just a little drone.

I guess you don't have the EVIC? You could just check to see if "Fuel Saver Mode" kicks on when you feel the bump.
 

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Discussion Starter · #8 ·
Nope, no EVIC but I'm pretty sure that is what I'm feeling. If it gets any worse I'll get it checked out but for now seems like it is probably somewhat normal.

Thanks guys
 

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When I'm cruising with cruise control on and start up a heal I can feel a small jerk and hear it happen in the exhaust. I'm assuming this is when MDS is kicking in the extra cylinders. Do others experience this? Is it normal or should I get it checked out?

Thanks
I think what you're feeling is the torque converter unlocking and spooling up a few hundred RPMs. Keep one eye on the tach next time you're in this situation. You can't feel MDS going on and off.
 

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I would think the car switching over to 4 cylinders would make the rpm of the engine change yet it doesn't. At 60 mph, I am at about 1750-1800 rpm no matter if I am running on 8 or 4.
 

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I guess you don't have the EVIC? You could just check to see if "Fuel Saver Mode" kicks on when you feel the bump.

Really? Wow, that's a nice, new touch. Older models do not have that option (my '06 doesn't, built 11/05).
 

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I think what you're feeling is the torque converter unlocking and spooling up a few hundred RPMs. Keep one eye on the tach next time you're in this situation. You can't feel MDS going on and off.
Sure you can. While the actual 4-to-8 transition may not contribute much to the little "nudge" that you can feel in some cases, the fact is that MDS makes our torque converter clutch behaviour pretty unique among most if not all modern cars: with MDS on, the torque converter clutch is actually slipping a bit.

It's the only application I've ever come across where a torque converter is purposely partially unlocked (pulse-width modulated, most likely) during a steady cruise situation!

When you get on the throttle gently to the point where you reach the MDS cutoff threshold, the remaining 4 cylinders will kick in but at the same time the converter clutch will lock 100%! So you get the weird situation where the RPM will actually go DOWN as you press on the accelerator! :)

As the TCC locks up 100%, depending on the amount of load on the engine you could feel a slight nudge as the RPM of the loaded-up motor is dragged down.

Sound-wise, while faint, I was most always able to detect the MDS transition by sound. When I removed the suitcase it became much more noticeable. I don't expect a regular R/T or an RT/R&T exhaust to make MDS noticeable, but definitely on a Daytona (of course, there could have been a muffler design change between the early and later '06 Daytonas).


So to the original poster: yes have a look at the tach when this happens, I'm thinking that unless the hill is really steep such that cruise control needs to really open up the throttle pretty wide, what you'll see is the RPM drop slightly (100 or 200 RPM tops) when this nudge happens. It's the TCC locking up 100% when all 8 cylinders come back online.
 

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I feel it and hear it everytime it happens in BOTH my Daytonas.... ;)
 

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I have noticed this also. I think triplertransam explained it very wel.
Randy
 

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Sure you can. While the actual 4-to-8 transition may not contribute much to the little "nudge" that you can feel in some cases, the fact is that MDS makes our torque converter clutch behaviour pretty unique among most if not all modern cars: with MDS on, the torque converter clutch is actually slipping a bit.

It's the only application I've ever come across where a torque converter is purposely partially unlocked (pulse-width modulated, most likely) during a steady cruise situation!

When you get on the throttle gently to the point where you reach the MDS cutoff threshold, the remaining 4 cylinders will kick in but at the same time the converter clutch will lock 100%! So you get the weird situation where the RPM will actually go DOWN as you press on the accelerator! :)

As the TCC locks up 100%, depending on the amount of load on the engine you could feel a slight nudge as the RPM of the loaded-up motor is dragged down.

Sound-wise, while faint, I was most always able to detect the MDS transition by sound. When I removed the suitcase it became much more noticeable. I don't expect a regular R/T or an RT/R&T exhaust to make MDS noticeable, but definitely on a Daytona (of course, there could have been a muffler design change between the early and later '06 Daytonas).


So to the original poster: yes have a look at the tach when this happens, I'm thinking that unless the hill is really steep such that cruise control needs to really open up the throttle pretty wide, what you'll see is the RPM drop slightly (100 or 200 RPM tops) when this nudge happens. It's the TCC locking up 100% when all 8 cylinders come back online.
Wow good info. Thanks. I still can't hear/feel pure MDS on/off in my Charger, which is stock. (i.e., if I'm cruising on flat land with cruise on, I never feel it, the only time I percieve anything is when on a hill or changing speeds or doing something else that could cause the converter to unlock)
 

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Yeah, the DCX powertrain engineers really scored a hit with MDS. To be able to make such dramatic changes in engine behaviour as seamless as can be in almost any driving situation... WOW! In my opinion it ranks right up there with any other innovation such as Honda's VTEC, variable valve timing, etc.

I've seen references to this partial unlocking being for improved smoothness in 4 cyl mode and I've seen some refering to a slight improvement in torque multiplication in the partially-unlocked converter. I think it's a bit of both.

1) for sure 4 cyl mode is going to be a bit rougher-running so I can accept that by partially unlocking the motor from the rest of the drivetrain there are going to be less vibrations transmitted to the occupants. For sure I can see that having an unlocked converter (at least partially) is going to make the 8-to-4 (and back) transition seem much smoother... let's remember that when 4 cylinders suddenly cease to suck in air at exactly the same RPM, the manifold vacuum is going to take a huge dump if the throttle blade(s) remain open to the same amount, so the electronic throttle's going to have to very quickly adjust itself the right amount in order to match the current V8 torque production. (which is not a bad thing: a "throttled" gas engine is inefficient, so a wider-open 4 cylinder will always be more efficient than a throttled V8). Any momentary "stumble" of the motor during this transition will be hidden by the less-than-solid connection to the rest of the drivetrain.

2) torque converters do provide torque multiplication in relation to the amount of "slippage" (the difference between the input and output shaft speeds of the converter). My Marauders used this to a scary amount: there was actually a very long point in the car's second gear operation where it actuated the converter clutch to a 50-60% duty cycle... long enough that for months I actually thought that THIS was 3rd gear! The RPM dropped enough that I was fooled, until I slapped on an Autotap and saw for myself that I was still in 2nd gear. Ford needed that "in-between" ratio to help deal with the fact that the 32V 4.6 was gutless under 3000 RPM and couldn't handle 3rd gear so soon, but couldn't stay in pure-unlocked 2nd in order to meet CAFE. Now, on our cars, we have maybe 100-200 RPM slippage when MDS is on? Barely noticeable by many except for those like me who remember doing 60mph at 1700 RPM yesterday on one road but today they're seeing 1900 RPM for the same speed on another road! So is there really much more multiplication going on at that small slippage? Probably not, but if they have to modulate the locking anyway for reason number 1 above, might as well make the best of it? (ie. the 4 cyl won't have to work as hard because the converter's helping out a bit). Nonetheless, with unlocked converters there is a loss of efficiency so I guess that may contribute to why shutting down half the engine's cylinders doesn't result in doubling the fuel mileage (along with the reasons of having to move all that extra deadweight from the "dead" cylinders, etc.).


So yeah, as a gadget and technology freak, all this MDS stuff gives me yet more driving enjoyment as I explore how it delivers great response in such varied driving conditions.

BTW, you want to hear MDS? Try driving a Brylcreem'ed Hemi in 0F or colder... you WILL feel the transition-surge and you definitely WILL hear the exhaust note change! LOL!
 

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Discussion Starter · #17 ·
LOL we don't get too many zero degree days here in central Texas!
 

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:)

Even with my stock Daytona exhaust last summer (temps in the low 90s), I could still hear MDS come on. It was very very faint, but I could tell if I was paying close attention. If anything, at the time it was more of a vibration change that I felt... you could feel more of the individual exhaust pulses in the seat of the pants along with a very faint distant deep "gurgle"... makes sense, because the remaining cylinders were now operating harder to deliver the same power as was coming from all 8 cylinders, so the individual ignition events are going to be more noticeable.

I can understand why the quieter R&T exhaust would make it even harder to detect. And forget the 340hp R/T version... I don't think it would be possible to hear any change there.

With Brylcreem though... :) I should take a quick video one of these days using the bullet camera I just bought.
 

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I can definitely hear the MDS kick in in my R/T(340 HP)
Is your car completely stock? If so, can you describe in your own words what you hear when MDS kicks in? (and are you sure it's MDS... many around my area seem to confuse MDS activity with the torque converter lockup).

Here's a test: cruise at a steady 60-65mph in [D], make sure your throttle position is 17% or less, preferably not lower than 13% (which would make it harder to hear the remaining 4 cylinders work harder during MDS, at those speeds). Move the transmission selector to [5] and see if you detect the exhaust note changes (again, for a completely stock R/T 340hp) as MDS is disabled. Study that exhaust note, and slide the selector back to [D] and within 2 seconds you should be hearing MDS kick back in.

If this isn't the sound you associate with MDS activity, then what you're hearing is not MDS.

If you can easily detect the MDS transition with the above test in your stock 340hp R/T, then we need to figure out why some 340hp owners can't hear MDS activity (heck, even some 350hp R/T R&T owners claim to not hear MDS!).
 
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