2014+ AFM (Active Fuel Management)

KARNUT · August 4, 2014

Have mine off with module and get 24 mph\g on highway going 70 mph.

At about 3000 miles I went 400 miles round trip at 75 mph I got 19 mpg, truck was stock except for muffler delete. This wk at 7000 miles I went on an 700 mile round trip, 72mph I got almost 22mpg with a Hypertech tune, no V4, on 93 shell gas.

Crf450r420 · August 5, 2014

At about 3000 miles I went 400 miles round trip at 75 mph I got 19 mpg, truck was stock except for muffler delete. This wk at 7000 miles I went on an 700 mile round trip, 72mph I got almost 22mpg with a Hypertech tune, no V4, on 93 shell gas.

V4 modes never applies at those speeds as it won't kick in unless you are going down hill do to friction from the wind. How ever I did see how rich it was on my dyno pull, so there is room for improvement in the fuel maps. Got info like this at speeds V4 applies? Anyone get a tune and leave V4 on have any info that applies to both?

KARNUT · August 5, 2014

V4 modes never applies at those speeds as it won't kick in unless you are going down hill do to friction from the wind. How ever I did see how rich it was on my dyno pull, so there is room for improvement in the fuel maps. Got info like this at speeds V4 applies? Anyone get a tune and leave V4 on have any info that applies to both?

I beg to differ at speeds up to 78 mph my V4 came on, on the flats and would pull some grades in V4. this was with cruise control on and fairly flat ground. It sounded like I had a fleet of helicopters on my tail.

calgator73 · August 5, 2014

I only notice the transition when the engine is under any load. Like other posters when it is noticed it feels like a gear change. Seems to stay in longer since I've transferred to 89. Love how quiet the truck is when turning 3500 rpms towing up a grade. No complaints.

Crf450r420 · August 6, 2014

I beg to differ at speeds up to 78 mph my V4 came on, on the flats and would pull some grades in V4. this was with cruise control on and fairly flat ground. It sounded like I had a fleet of helicopters on my tail.

Sierra getting better aero? I'm pretty familiar with flat driving as I have to drive 3.5 hours to get to a hill. Never had it come on below 65 without drafting a semi with a tailwind on flat ground.

KARNUT · August 6, 2014

Sierra getting better aero? I'm pretty familiar with flat driving as I have to drive 3.5 hours to get to a hill. Never had it come on below 65 without drafting a semi with a tailwind on flat ground.

That would defeat the purpose of having it, if it didn't come on after 65. My truck has stock wheels, a bed cover, 345 rear. It would come on at 75 mph often, that's the main reason I got a can tune, under 60 I ran in M5 to keep it off. Ive had few trucks with this feature they all would come on after 65 all got tuned out, something wrong with your truck?

Crf450r420 · August 6, 2014

I guess there is something wrong with my truck then. Of course, I don't have your custom 345 rear end. I do however have the stock 3.42 rear end with stock tires and a hard bed cover. I also don't have running boards hanging out in the air. Sounds like most of the people on here need to learn what wax you use to reduce your wind friction because most people don't see it above 65 without going down a hill.

KARNUT · August 6, 2014

I guess there is something wrong with my truck then. Of course, I don't have your custom 345 rear end. I do however have the stock 3.42 rear end with stock tires and a hard bed cover. I also don't have running boards hanging out in the air. Sounds like most of the people on here need to learn what wax you use to reduce your wind friction because most people don't see it above 65 without going down a hill.

Yes right 342, I swear my truck spent a lot of time in V4 over 65 on the free way. It would hit V4 in 5th and stay shifting into 6 under light acceleration I hated the sound. I drove in M5 in town and when I got on the free way I would click up to 6 and V4. That's why I spent the money on the tune, I have custom exhaust and didn't like the V4 sound. No need to be an a.. and talk about special wax, not my first cylinder deactivation truck. We will just have to disagree.

KARNUT · August 6, 2014

Yes right 342, I swear my truck spent a lot of time in V4 over 65 on the free way. It would hit V4 in 5th and stay shifting into 6 under light acceleration I hated the sound. I drove in M5 in town and when I got on the free way I would click up to 6 and V4. That's why I spent the money on the tune, I have custom exhaust and didn't like the V4 sound. No need to be an a.. and talk about special wax, not my first cylinder deactivation truck. We will just have to disagree.

Well I read the whole thread, I wanted to see just how many people said their truck wouldn't go into V4 on flat terrain after 65 MPH, I found no one. Could you point the thread out to me? I did see a few post on Hwy V4 operations though. I didn't think I had the only one that would cruise in V4 on flat terrain after 65.

Crf450r420 · August 6, 2014

Second post, guy admits it will only go into V4 after 65 in the right conditions, because starting at 45 wind adds resistance to moving and by 65 it has added enough that the truck doesn't get more MPG in V4 over V8. If I could get into V4 at 70 I'd get better than the rated MPG, but as it is I get about the rated MPG at 70 mph going between 19 and 21 depending on the winds in relation to my direction. I have not tried the trailer tow mode that high yet, but found down low that it often is a wash as the higher revs in V4 use as much fuel as V8 in the next gear. I'm not trying to be an ass by stating the facts of it normal because of physics. V4 is not an interstate help or they would have a better highway rating for MPG. I'm currently running 48 psi in my tires and truck is stock exterior except for the hard bed cover and power steps and with cruise control still no V4 flat ground. If you are in fact getting it to work more than most I'd love to learn how. No point in using more gas than I need.

Edited August 6, 2014 by Crf450r420

KARNUT · August 6, 2014

Second post, guy admits it will only go into V4 after 65 in the right conditions, because starting at 45 wind adds resistance to moving and by 65 it has added enough that the truck doesn't get more MPG in V4 over V8. If I could get into V4 at 70 I'd get better than the rated MPG, but as it is I get about the rated MPG at 70 mph going between 19 and 21 depending on the winds in relation to my direction. I have not tried the trailer tow mode that high yet, but found down low that it often is a wash as the higher revs in V4 use as much fuel as V8 in the next gear. I'm not trying to be an ass by stating the facts of it normal because of physics. V4 is not an interstate help or they would have a better highway rating for MPG. I'm currently running 48 psi in my tires and truck is stock exterior except for the hard bed cover and power steps and with cruise control still no V4 flat ground. If you are in fact getting it to work more than most I'd love to learn how. No point in using more gas than I need.

Wow your just as stubborn as me, I figured more people would jump in on this to get more info on the V4 on the HWY. I tuned mine out cause I saw no gain, just the annoying V4 drone on the HWY. Lets call it a draw ( even though Im right) LOL. I saw what I saw and heard what I heard.

ryandemo84 · August 6, 2014

The fastest I set my cruise at with V4 on the hwy was 72. That is on complete flat hwy on a recent trip from LA to FL. However on my daily drive to work I drive over 70 on hwy with several overpasses causing it to go in and out of V4 which is more aggravation than benefit. Its not so much the drone but that it feels like it keeps shifting. I am actually thinking of getting a tune to delete AFM as it doesnt benefit me much. My truck is CC 5.3 with 3.42.

KARNUT · August 7, 2014

Its going to take flat ground for sure, even then it will come and go. But the point I was trying to make was, its not just going to come on down hill after 65, you would be at fuel shut off any way.

Crf450r420 · August 7, 2014

I tried the tow mode last night and it doesn't help much. The extra revs need more fuel. Looked like maybe a .5 mpg improvement at the most. I also thought about another thing. I have a transfer case that probably adds drag. You two have 2WD trucks?