New cars with the longest ranges?

[LTC8K6]

I didn't think the 6.1L had MDS. I think the new 6.4L does.

My 5.7L GC has MDS. There's a message on the dash when it's running on 4 cylinders. It still drops into 4 cylinder mode even at 80mph.

There have been a few TSBs to make adjustments to the MDS system.

Here's a graph of the typical early hemi MDS duty cycle. I would say my GC runs on 4 cylinders quite a bit, especially if you use the cruise control.

http://www.wkjeeps.com/engine/mds_graph2.jpg

 

[Childs]

That depends. On the SRT8s at least, MDS is very, very conservatively set up. It only kicks in when power demand is incredibly low. In fact, unless you're going downhill, the air-resistence once you hit 70ish is enough that it won't ever come on unless you are losing speed.

I don't know how it is set up on the 5.7L R/Ts though.

It kicks in all the time in my Challenger R/T. If I am not accelerating it comes on after a couple seconds. I am in ECO mode 90% of the time.

 

[LTC8K6]

What Chrysler, and everyone else, has done with newer cars is to make the fuel cutoff much more aggressive. The engine computer cuts the fuel off at the slightest opportunity in the 2012 GC. I think this causes optimistic MPG readouts. For the V6, the ECO indication on the dash is when the fuel has been cut.

Chrysler calls it iDFSO, intelligent Deceleration Fuel ShutOff.

 

[LTC8K6]

It kicks in all the time in my Challenger R/T. If I am not accelerating it comes on after a couple seconds. I am in ECO mode 90% of the time.

Not sure if ECO indicates iDFSO or 4 cylinders on the Hemi engines or if they also say Fuel Saver for 4 cylinder mode. The GC owner's manual seems to indicate both. ECO for fuel cutoff and Fuel Saver for 4 cylinder mode.

I drove a 2012 Hemi, and as I recall, it never displayed Fuel Saver, just ECO.

 

[Childs]

Not sure if ECO indicates iDFSO or 4 cylinders on the Hemi engines or if they also say Fuel Saver for 4 cylinder mode. The GC owner's manual seems to indicate both. ECO for fuel cutoff and Fuel Saver for 4 cylinder mode.

I drove a 2012 Hemi, and as I recall, it never displayed Fuel Saver, just ECO.

I have never seen Fuel Saver on the EVIC. It is my understanding that MDS cuts fuel to 4 cylinders, and this is what ECO represents. I do not think there is a separate Fuel Saver/fuel cutoff feature apart from MDS. At least not in a Challenger.

 

[LTC8K6]

I have never seen Fuel Saver on the EVIC. It is my understanding that MDS cuts fuel to 4 cylinders, and this is what ECO represents. I do not think there is a separate Fuel Saver/fuel cutoff feature apart from MDS. At least not in a Challenger.

Oh yes, the Challenger will definitely have iDFSO. It will definitely be cutting off the fuel when you are decelerating.

I think that on cars without MDS, ECO indicates the fuel cutoff, and on cars with MDS, ECO indicates 4 cylinder mode, and there is no separate fuel cutoff indication.

One thing you can do if you have the auto trans is to manually select 5 instead of D. This will turn MDS off.

If you still get an ECO indication, then ECO may only be indicating the fuel cutoff, or it may be indicating both the cutoff and MDS. Or not.

The owner's manuals are confusing, because they don't match what the vehicle actually displays. The Challenger owners manual says FUEL SAVER indicates MDS, and ECO indicates that you are driving with good economy. But I believe they got rid of the FUEL SAVER display and just have ECO.

I think ECO indicates fuel efficiency, whether MDS or iDSFO or just driving like grandma.

 

[LTC8K6]

My 2008 Jeep says FUEL SAVER when MDS is active. There is no ECO display. The ECO was added in 2009, I think.

 

[LTC8K6]

http://www.fleetchrysler.ca/en/innovation.php

 

[JTsyo]

So how hard is it to mod you car with a bigger tank or an aux one?

 

[Childs]

I think that on cars without MDS, ECO indicates the fuel cutoff, and on cars with MDS, ECO indicates 4 cylinder mode, and there is no separate fuel cutoff indication.

One thing you can do if you have the auto trans is to manually select 5 instead of D. This will turn MDS off.

If you still get an ECO indication, then ECO may only be indicating the fuel cutoff, or it may be indicating both the cutoff and MDS. Or not.

I think this is probably the case. I see MDS on when maintaining a constant velocity or a very gradual acceleration, which is probably why its almost always on. Unless I'm alone as far as I can see, I tend to drive fairly conservatively. While IDFSO could be working in situations where MDS would be in use at the same time, there are situations where IDFSO won't be working and MDS is. This is when ECO is displayed. When using the paddle shifters I have never seen ECO on, but you are actively shifting to keep the rpms optimal, so I don't think IDFSO would ever work in that case anyways. I suppose I could leave it in 5th and coast off the hwy tonight to see if it comes on.

 

[soccerballtux]

You would have to be driving under the most ideal conditions to get that mileage and do so for hrs on end. Not going to happen in the real world. I have a close friend that has one and if he pulled 17, that would be good.

oh : (

 

[soccerballtux]

Buddy who test drove the hemi 392 model told me the 8 speed is very efficient,when it got up to highway speed,either there was a option or engine function that would shut off 4 of the cylinders and mpg would just sky rocket.

Same for the v6?

Weird, why did no manufacturers do this before? Doesn't make sense.

 

[Ferzerp]

One thing you can do if you have the auto trans is to manually select 5 instead of D. This will turn MDS off.

Only when you feel like shifting manually. You put it in 5th, it's staying in 5th until you slow down to stop. It's not going to change. Not on the SRT anyway.

Beyond the odd sound, MDS is so conservative that it's rarely on.

 

[Ferzerp]

Buddy who test drove the hemi 392 model told me the 8 speed is very efficient,when it got up to highway speed,either there was a option or engine function that would shut off 4 of the cylinders and mpg would just sky rocket.

Same for the v6?

None of the 6.4L engines are paired with an 8-speed currently. Probably can't handle the power.

 

[Ferzerp]

Weird, why did no manufacturers do this before? Doesn't make sense.

Cadillac/GM tried..... They failed. Big time.

GM and Honda did it recently too.


It seems much simpler to implement on pushrod engines, too.

 

[LTC8K6]

Only when you feel like shifting manually. You put it in 5th, it's staying in 5th until you slow down to stop. It's not going to change. Not on the SRT anyway.

Beyond the odd sound, MDS is so conservative that it's rarely on.

MDS is nearly constantly on with my 5.7L if I am not on the gas. I can even get some light acceleration in 4 cylinder mode.

With my trans, putting it in 5 just cancels MDS. It shifts normally.

Putting it in 4 gives me 1 thru 4, etc.

It doesn't stay in that gear like the SRT's do.

 

[LTC8K6]

Weird, why did no manufacturers do this before? Doesn't make sense.

GM's Active Fuel Management is fairly widely used and works just as well.

Honda has it as well on their high end V6. Honda has 2 stages, down to 4 cylinders, and down to 3 cylinders. Variable Cylinder Management.

MPG goes up a little bit on the highway.

No skyrockets. :biggrin:

 

[LTC8K6]

Mine sounds like a John Deere tractor in need of a tuneup when it drops into V4 mode.

 

[Childs]

One thing you can do if you have the auto trans is to manually select 5 instead of D. This will turn MDS off.

FYI, ECO never comes on when coasting in 5th, or breaking. Coasted from 65 mph down to 20 or so before I used the break.

 

[LTC8K6]

FYI, ECO never comes on when coasting in 5th, or breaking. Coasted from 65 mph down to 20 or so before I used the break.

It's probably only indicating MDS then, and you have no indication of the fuel cutoff.

If you get a scangauge, you can see the iDFSO in action.

Keep in mind that all modern cars with fuel injection shut the fuel off on deceleration. Unless your car is very old, it is shutting off the fuel when you decelerate.

iDSFO is just a better controlled implementation of it.

 

[Squisher]

Yea Haw, just add a 50 gallon auxiliary tank to bed of the truck.