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So we'd agree that the MDS light will come on when in 4 cylinder mode (and you state it also comes on when getting better mph). Regardless, it use to go into MDS mode when using the accelerator to maintain speed. Now it will only come on when removing all pressure from the accelerator. The only thing I've changed is the mufflers. It was working that way an hour before install and the next day it was not working that way.
You keep saying MDS light. Does 14 have a seperate light that says MDS or 4 cylinder as well as a ECO? Or just ECO?
 

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You keep saying MDS light. Does 14 have a seperate light that says MDS or 4 cylinder as well as a ECO? Or just ECO?
Punisher69 relates to a backpressure sensor that may report to the computer...I believe it is Not necessary to have the sensor...I feel the software notices a loss of Torque...and realizes too much strain on the eng dropping to 4 cyl..[very heavy car]....therefore prevents MDS...I found this statement in a PDF file of engineers discussing backpressure:
"it depends on what you are trying to do. It will change the torque-horsepower curve. In simplistic terms, reducing the backpressure will decrease torque and increase horsepower. So what is it that you are looking for? Reducing the pressure to zero, by removing the exhaust system completely is going to cause problems, as is restricting it so much that the engine can’t rev. Compromises are made to find the proper operating condition "

Back pressure is only useful in certain conditions. (AKA like a two stroke ) These cars are not the that condition. Having a tuned exhaust that promotes better scavenging of gases will perform better than a just huge diameter exhaust pipe everywhere on a four stroke engine. Once again, Scavenging is the key word, not back pressure.

Also always welcome to always link to that PDF file.
 

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You keep saying MDS light. Does 14 have a seperate light that says MDS or 4 cylinder as well as a ECO? Or just ECO?
My 14 only has an "ECO" light, no direct indication of 4 cyl mode. Unless his is special he has no MDS light.
 

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Stated...Scavenging is the key, Not backpressure"...I believe is certainly true...But I also believe it's for the purpose of gaining HP...at the sacrifice of toque...These engines run relatively low RPM when in MDS...and it is "torque that is in demand"...I would think most of us know how difficult it is to maintain staying in 4 cyl mode...My guess..it's cuz of borderline torque available...and the computer is carefully watching the load placed upon the eng....IMO, Slight loss of torque from exhaust mods...are enuf., and computer says "No"... Have noticed some other members have changed the exhaust and not lost 4 cyl mode...Maybe couple different model yrs , different .software...?
 

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Horsepower is a function of torque and rpm, so your two ways of increasing horsepower are by making more torque or revving higher. An exhaust doesn't let you rev higher so if you make more hp at a given rpm as a result that means you've added torque. To your point you may end up shifting the power curve though.
 

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No... sorry. I was jumping back and forth from something else. It is only an ECO light.
The as stated, the ECO light is not a MDS indicator. Both can operated 100% independently. You can ECO lit eon without MDS, and you can have MDS on without the ECO lite. Both do share some of the same operating parameters though.

MDS is looking at speed, oil pressure, oil temps, engine load, throttle position (from my understanding) to determine operation of the MDS solenoids and lifters.

ECO light looks at speed, engine load, throttle position to showcase rather you are driving the car in a "economically" fashion.

Both however will not work if there is any Check engine lights or codes.


I can not explain why it is what is happening with your car. Over the internet kinda hard cause your description may be different of the same situation than mine. Perhaps if you can make a video of inside windows rolled up of you on highway, doing 50-60 ish level ground. give it good throttle, hold it, then back off and set cruise. If camera can pick up exhaust note may help.
 

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You learn something new everyday. I always thought when I saw, "ECO" on my dash that I was in 4-cyl mode. Didn't know that that is not always the case.
 

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OP, if it's that important to have MDS operating, unhook the battery cables for about 30 min (if you haven't already). Also, pull the #11 fuse for a bit and put it back in. This will reset all the adaptives and may have you working again.

So many things could have happened. If they didn't unhook the battery when they welded in the mufflers, there could be an electrical issue, again the CEL should be on. I actually cooked an aftermarket amp not unhooking the battery while doing exhaust work.

I do have some good news for you though. There honestly isn't 2mpg difference between ECO and not. Most of us with exhaust work have eco disabled anyhow because it sounds like poop in 4cyl mode.

Sent from my moto z4 using Tapatalk
 

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OP, if it's that important to have MDS operating, unhook the battery cables for about 30 min (if you haven't already). Also, pull the #11 fuse for a bit and put it back in. This will reset all the adaptives and may have you working again.

So many things could have happened. If they didn't unhook the battery when they welded in the mufflers, there could be an electrical issue, again the CEL should be on. I actually cooked an aftermarket amp not unhooking the battery while doing exhaust work.

I do have some good news for you though. There honestly isn't 2mpg difference between ECO and not. Most of us with exhaust work have eco disabled anyhow because it sounds like poop in 4cyl mode.

Sent from my moto z4 using Tapatalk

City there is min gain. Highway however I lost little over 4-5 mpgs.
 

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Soooo, What did we learn here ?...That tcope was mistaken about 'loosing the 4 cyl mode"...and the reduced backpressure merely effected ECO light? Surprised that his hearing could not determine whether in 4 cyl or not ! Perhaps understandable, with straight pipes sound...!
 

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Discussion Starter #32
Soooo, What did we learn here ?...That tcope was mistaken about 'loosing the 4 cyl mode"...and the reduced backpressure merely effected ECO light? Surprised that his hearing could not determine whether in 4 cyl or not ! Perhaps understandable, with straight pipes sound...!
According to the manual, the ECO light is an indicator of the engine being in MDS mode (it was then commented that it also included an "efficiency" indication). There has been no dispute that this is the case. I've never been able to hear it switch to 4 cylinder mode. I don' think this is unusual. This was true with the stock exhaust as well.
 

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Discussion Starter #33
OP, if it's that important to have MDS operating, unhook the battery cables for about 30 min (if you haven't already). Also, pull the #11 fuse for a bit and put it back in. This will reset all the adaptives and may have you working again.
So I looked into pulling fuse 11. Most of the posts I saw were from 2010 and prior (I have a 2014). I checked the hood fuses and the trunk fuses and I don't think #11 is the correct fuse in my vehicle. I'll keep looking for the correct fuse... or it may just be that a disconnect of the battery or awhile will reset this.

Engine:
291217


Trunk:
291218
 

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Discussion Starter #34
The as stated, the ECO light is not a MDS indicator. Both can operated 100% independently. You can ECO lit eon without MDS, and you can have MDS on without the ECO lite. Both do share some of the same operating parameters though.
From the manual:

This icon will appear whenever the Multi-Displacement System (MDS) (if equipped) allows the engine to operate on four cylinders, or if you are driving in a fuel efficient manner.

According to the manual, this mean the ECO light will come on whenever the engine is in MDS mode. It then states that it will also come on when driving in a "fuel efficient manner". It will come on when in MDS mode... so this will always happen. Or it can also come on when running in a "fuel efficient manner". While this may not be correct... it is what the manual states.


I can not explain why it is what is happening with your car. Over the internet kinda hard cause your description may be different of the same situation than mine. Perhaps if you can make a video of inside windows rolled up of you on highway, doing 50-60 ish level ground. give it good throttle, hold it, then back off and set cruise. If camera can pick up exhaust note may help.
I can record a video while displaying information from the OBD system on the same screen. I looked at it last night and there are some throttle readings that I can display. I could then record the light in the video as well. But the light decently only comes on when decelerating. As soon as I put even the lightest of pressure on the pedal it turns off (not even enough to maintain the current speed on level ground).

Good info... good discussion.
 

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From the manual:

This icon will appear whenever the Multi-Displacement System (MDS) (if equipped) allows the engine to operate on four cylinders, or if you are driving in a fuel efficient manner.


According to the manual, this mean the ECO light will come on whenever the engine is in MDS mode. It then states that it will also come on when driving in a "fuel efficient manner". It will come on when in MDS mode... so this will always happen. Or it can also come on when running in a "fuel efficient manner". While this may not be correct... it is what the manual states.



I can record a video while displaying information from the OBD system on the same screen. I looked at it last night and there are some throttle readings that I can display. I could then record the light in the video as well. But the light decently only comes on when decelerating. As soon as I put even the lightest of pressure on the pedal it turns off (not even enough to maintain the current speed on level ground).

Good info... good discussion.
On the light,

MDS can be active without the light. Light can be active without MDS. As I said, they both share alot of the same operating parameters for function so it is naturally on when either or may be happening. Does not mean it always will be so using it as a sure fire indicators is incorrect. Before I deleted MDS I could be on the highway and keep the car in MDS mode, but never see the ECO light by applying throttle. Or driving above 80.

Fuse 31 Top box I believe is ECM.


Do you have a tuner on it by any chance? I forget if you mentioned it or not.
 

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Discussion Starter #36
On the light,

MDS can be active without the light. Light can be active without MDS. As I said, they both share alot of the same operating parameters for function so it is naturally on when either or may be happening. Does not mean it always will be so using it as a sure fire indicators is incorrect. Before I deleted MDS I could be on the highway and keep the car in MDS mode, but never see the ECO light by applying throttle. Or driving above 80.

Fuse 31 Top box I believe is ECM.


Do you have a tuner on it by any chance? I forget if you mentioned it or not.
I'm open... but as I quote, the manual states if MDS is active, the ECO light is on.

I do have a tuner.
 

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I'm open... but as I quote, the manual states if MDS is active, the ECO light is on.

I do have a tuner.
Oh I know. And if I didn't see physically how and what the car does (mines a 2011 Pursuit BTW) I wouldn't argue an alternative point. I drew my opinion from watching both of the actions of MDS and the ECO light in relation to each other.


What kind of Tuner, Tune, and what are the Throttle Booster settings? When did you put the tune on in rleation to the exhaust install?

Possible the TB booster may be up big high. I tried out a high setting on mine and noticed ECO light (without MDS as I deleted it but car did come with it) would quickly go off with throttle input. And I didn't like how the car behaved so I dropped it back down. Wanna say 5% or so.
 

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Discussion Starter #38
Oh I know. And if I didn't see physically how and what the car does (mines a 2011 Pursuit BTW) I wouldn't argue an alternative point. I drew my opinion from watching both of the actions of MDS and the ECO light in relation to each other.
I'm not 100% convinced that the ECO light is not as mentioned here, really only comes on when the system "thinks" it's getting good fuel usage. I've had this type of ECO light on a vehicle before and used the option to turn it off as it was pointless (basically, press lightly on the go pedal and it tells you fuel economy is good. Yeah, no kidding. But on my charge it was coming on when maintaining a speed. Now it's not doing that. It kind of makes me think I'm getting worse mpg from the muffler change. However, perhaps I'm jus throwing off once of it's calculations so it is no longer valid. This is what I'd like to try to figure out. That is, I'm more curious in knowing how my car is running/operating rather then overly concerned.


What kind of Tuner, Tune, and what are the Throttle Booster settings? When did you put the tune on in rleation to the exhaust install?
It is a Diablosport tuner.

The tune is an email tune to go with my Procharger. But yes... the ECO light was operating after the supercharger and the tune just as it had been before. It was only after the last muffler change that it more or less stopped working.

About the only other difference I can think of is that I've not driven the vehicle on the highway for long periods of time in the cold weather since the muffler change. But I've drive it for 30 minutes or so around town and then been up on the highway for 5 minutes or so. So I don't think that would change anything.

Today I just disconnected the battery for an hour. No change to operation.
 

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If you have a Diablo, you should be able to data log while driving. It won't show you ECo light stuff but you can see enough to see what is going on.

However, I wonder if with that tune of MDS was turned off. I am unsure how MDS would work out with a S/c on the vehicle and chances are really really good that MDS has been turned off and that is why you have never noticed any sound transition with it. Honestly, you should have mentioned this from the get go then all this would have been shorter in discussion.



***added note, after 5 mins of searching running MDS with a boosted application is basically a 100% no no. So I pretty sure your tune has MDS turned off. So MDS really isn't the issue here.


How many miles since the install and subsequent tune? How many miles since tune and muffler removal?
 

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You can go into the Uconnect menus and in the "Display" menu there's a "Fuel Saver Display" setting where you can turn it On/Off. If the setting is On, the ECO icon will display whenever you're driving in a fuel efficient manner; regardless of MDS. Of course MDS may also be engaged if you're driving in a fuel efficient manner. MDS will be disabled if you have a custom performance tune or you disable MDS using the Diablo Modify Parameters menu. I have the Fuel Saver Display setting Off and MDS disabled with a custom tune. For me the ECO icon displayed in the EVIC is just a fading memory.
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