2014+ AFM (Active Fuel Management)

[gmc1]

First time poster, but long time browser...

 

I definitely notice the switching between modes and unlike others, I seem to notice it more as the speed increases. It almost seems like my truck is trying to stay in V4 mode longer then it should..for example, on a small uphill I will start to put my foot in the throttle to keep my speed and it will stay in V4 so I keep pressing the gas and then it feels like it downshifts as it finally switches into V8 mode. Not sure if that's normal or not but it does bug me. This is my first GM with AFM...Kinda makes me miss my old 2011.

 

 

 

Yeah that. Totally agree. Maybe since it is a new truck/engine there will be some future software updates that address this, hopefully. Or a custom tune if all else fails.

[pm26]

I could probably not tell when it kicked in on my hemi motor because it probably never did. The fuel mileage on that engine was amazing I could get almost 10mpg and I drove it like a granny. What was even better was that it had about a 17-18 gallon tank so I could almost get far enough away from the house so that I could not walk back and get a gas can when it ran out of gas.

Is the HEMI fuel economy really that bad? I wonder what it does in a 2500 series RAM which does not have the cylinder deactivation.

[Chris]

I could probably not tell when it kicked in on my hemi motor because it probably never did. The fuel mileage on that engine was amazing I could get almost 10mpg and I drove it like a granny. What was even better was that it had about a 17-18 gallon tank so I could almost get far enough away from the house so that I could not walk back and get a gas can when it ran out of gas.

Is the HEMI fuel economy really that bad? I wonder what it does in a 2500 series RAM which does not have the cylinder deactivation.

12-13 highway. Got one and dont like it.

[reldridg]

Is the HEMI fuel economy really that bad? I wonder what it does in a 2500 series RAM which does not have the cylinder deactivation.

I had a Jeep Grand Cherokee Limited with the 5.7 Hemi, and it never got good gas mileage, on the open highway on a road trip we would see up to 15 mpg, normal mixed driving it would get around 11 mpg, if I went through a whole tank in the city we would see around 9.5 mpg. I do not put many miles on in a year so I never chased that cat as to why the mileage was so bad, I doubt the other hemi's are like that or else everyone would hear about it.

 

I have been driving jeeps for 23 years, and the taste from this last one steered me well away from Chrysler products I read these forums with some of the issues going on with the new 1500s and a lot of the issues sounds like a good day I had with that jeep.

 

The last straw was I took it in for a safety recall for the electronic transfer case shifting mechanism. Well the safety recall really worked because once I got it back I could no longer shift into 4lo. The dealership and manufacturer said that meant there was already a problem with the circuit board and it would only cost me around $850-$1000 to fix.

 

I felt like I went to the doctor and he punched me in the face and then tried to charge me for fixing a broken nose Be very leery of safety recalls.

[Joe_K]

Is the HEMI fuel economy really that bad? I wonder what it does in a 2500 series RAM which does not have the cylinder deactivation.

 

Yes, it's horrible. My window sticker said 20 hwy, no way it touches that. Read the forums, even the new ones with the 8-speeds aren't getting anywhere close to the sticker. With my Silverado, I can beat the sticker if I take it easy.

[MikeNH]

I could probably not tell when it kicked in on my hemi motor because it probably never did. The fuel mileage on that engine was amazing I could get almost 10mpg and I drove it like a granny. What was even better was that it had about a 17-18 gallon tank so I could almost get far enough away from the house so that I could not walk back and get a gas can when it ran out of gas.

Is the HEMI fuel economy really that bad? I wonder what it does in a 2500 series RAM which does not have the cylinder deactivation.

 

Until this year HD trucks were exempt from CAFE regulations so Chrysler had no reason to use it. That and I'd guess they don't want it on a truck that is more likely to be worked compared to 1500s which are used as big cars by many owners.

[ZmanII]

I had a 04 5.3 with a 4 speed, then I bought an 11 5.3 with a 6 speed. On paper the 04 was supposed to get 18 mpg highway and the 11 on paper 21 mpg highway. In real life, the 04 got 20 mpg highway and the 11 got 21 mpg. I think the 1 mph came from the extra gears in the tranny. I don't feel AFM buys you much. City mileage is within 1 mpg of the two vehicles also.

 

One major difference in highway mileage I have seen in my trucks is the actual speed, anything over 73 mph, the gas mileage nose dives, at least several miles per gallon. Under that, they get reasonable mileage. When I refer to the 20-21 mpg averages, that is for a full tank, so a 550-600 mile average.

[BringTheRain403]

I never notice it unless I'm looking for it...

 

Sent from my SCH-I535 using Tapatalk 2

 

 

[pm26]

Yes, I think that worrying about your truck's fuel economy too much is a moot point. In my case I drive a lot including a pretty long commute to work, so I use a car for most of my driving and use the truck when I need it, that is for towing my boat and for hauling. Heck, driving at least 35k miles a year, I would go bankrupt if I had to drive only my truck which gets 15 MPG city and 17 highway. I put about 340k miles on my Mazda 626 between 1999 and 2012, and 67k on my Impala in just last two years.

Edited January 9, 2014 by pm26

[Silver space ship]

I live in MN and it's been cold all winter and with the cold my v4 hardly gets used. Most mornings on my 17 mile trip to work it doesn't even go into v4. On the way home when temps might be slightly higher then in the morning it will usually go into v4 in the exact same place on the road but usually kicks back out another 1/2 mile or so down the road. I might see 1/4 mile stretch 2 to 3 times again before I get home where it's in v4.

 

Today I picked up 840 lbs of wood pellets to help offset the $5 plus a gallon propane price. The 840lbs was all in the bed of the truck and I decided to put the truck in tow haul mode. The temp was -17 and the wind was coming from my side, I could see it in the snow blowing across the road and a few flags I drove by. My truck went into v4 about 6 miles down the road (about the same time I put it in tow haul) and stayed in v4 as good or possibly better then when I'm empty in the summer. I could go up some small hills and stay in v4 and also accelerate on the flat road. Other then the bigger hills my truck stayed in v4 doing 60mph to 63mph. I just don't get it! I have almost a 1/2 ton of weight in the bed and now it decides to be fuel efficient! I would have though that tow haul wouldn't allow V4 or at least really limit how much it can use it.

[pm26]

Next time put at least 2,000 lbs in the bed of the truck and hope it will stay in the V4 mode permanently!

 

The only explanation I can offer for the thruck staying longer in the V4 mode with the load is that you drove a lot less agressively with the load and used less throttle.

Edited January 28, 2014 by pm26

[seamonster]

Perhaps you were in a lower gear(because of the tow haul) which would make more rpm's and

maybe enough torque to make the v-4 work better. Try locking out 6th gear and seeing if the v-4 mode

works better. What gears do you have? 3.08?

[Silver space ship]

3.43

[ChevyZ71LTZ]

Or the truck stayed in a proper gear for longer and didnt have to downshift and rev up like without tow/haul mode

[pm26]

3.43

3.42

 

And ChevyZ71LTZ has a point, using the tow/haul mode is the most logical explanation for the increased time in the V4 mode.

Edited January 28, 2014 by pm26