2014+ AFM (Active Fuel Management)

14SLTZ71 · September 1, 2014

Could be worse! Im all fired up now LOL . Im calling the dealer and tell them Im coming by to look for my phone charger. See what the hell they are doing. Insert OO7 theme in HERE.

Hopefully it's not sitting in the back lot where they have been canibalizing parts off it to repair other vehicles. Or maybe that would be a good thing?

Edit: Sorry for High-jacking...

Edited September 1, 2014 by 14LTZZ71

scott19677 · September 1, 2014

Wish me luck. Im fighting for all of us. see ya.

14SLTZ71 · September 1, 2014

Not true, anytime you decelerate (foot off the gas) in v4 or v8 and the mpg reads 99 mpg there is ZERO fuel used. The injectors are not even open. There is absolutely no good reason to burn fuel if the engine is spinning above 1000 rpm. You could say the engine is dead and fuel is added back just before it returns to idle. It's also in open loop mode since there is nothing to monitor on the o2 sensors since there is no combustion.

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Can you provide documentation that supports your claim (foot of gas, zero fuel used) since your callin someone out? If this is the case, what is keeping the engine running if it's burning ZERO fuel.

MikeNH · September 1, 2014

Can you provide documentation that supports your claim (foot of gas, zero fuel used) since your callin someone out? If this is the case, what is keeping the engine running if it's burning ZERO fuel.

Go ask google. It's fairly common for the engines to cutoff fuel use for short durations and let momentum keep things moving.

bass mechanic · September 1, 2014

Yes I can easily prove it, it's a known fact! The only thing keeping the engine running is the fact you have a 6,000 lb truck rolling to a stop. The engine still spins, just no fuel used. Every manufacturer uses this fuel cutting technology! How else do you explain 99 miles per gallon, on my ultra gauge it shows 999.99 miles per gallon is as close to infinity as you can display with 5 digits. Because literally if you had a long enough hill you could roll forever without using any fuel. For the same reason the instant reads 0 when your stopped, cause your using gas, but not covering any miles.

As a matter of fact the next time your headed down a small hill depress the gas pedal as you watch the instant mpg go from 99 to any other number, you can hear and just barely feel the engine start making power.

Here is another trick, while costing down hill shift to neutral, at 70 mph you should see about 65-75 mpg instant because now your using fuel to make the engine idle. That much fuel needed at 70 mph equals that much instant fuel economy without even driving the truck, it's coasting!

So when you try the neutral make note of the instant mpg. Now put it in gear and give it just a tiny amount of gas, you'll find it's impossible to get any mpg between 99 and the 65-75 you got at idle, the reason is because the truck will not use any less fuel than it did at idle

Because below that amount is not providing any benefit to making the truck go any faster. It's only wasting gas so it cuts fuel off

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14SLTZ71 · September 1, 2014

Go ask google. It's fairly common for the engines to cutoff fuel use for short durations and let momentum keep things moving.

I never said I agree or disagree. I said if your going to call someone out on something you should provide documentation to support your claim. He didn't call me out.

Edit: your opinion doesn't mean squat at that point.

Edit: and preferably documentation from GM since it's a GM engine design and should discuss their fuel management and delivery technology for their direct injection truck engine.

Edited September 1, 2014 by 14LTZZ71

bass mechanic · September 2, 2014

I never said I agree or disagree. I said if your going to call someone out on something you should provide documentation to support your claim. He didn't call me out.

Edit: your opinion doesn't mean squat at that point.

Edit: and preferably documentation from GM since it's a GM engine design and should discuss their fuel management and delivery technology for their direct injection truck engine.

GM is not going to share their technology with anyone. the bottom line is that i know what i am talking about! every manufacturer does it, it's a common practice. my tacoma used to go to fuel cutoff at 1700 rpm and higher. the GM seems to be cutting fuel around 1,000 rpm.

just keep in mind the engine doesn't have to be "running" it can still be "spinning" and not using any fuel.

look at it this way.. an engine when running is simply spinning things. its turning the alternator, water pump and all the other accessories on the front, and turning the gears and drivetrain at the back.

when your coasting down a hill everything is still turning and that never changes.

but it shouldn't be too hard to believe it is possible to cut the fuel when the vehicle is spinning the engine faster than the combustion process is at idle.

when this happens, they turn off the fuel. why would you need to continue to add fuel to an engine that the driver is commanding 0 torque from?

seems pretty obvious to me.

you can choose to believe it, or not.. doesn't affect my life any! just trying to share some common knowledge with you. you can call me out if you want, and i don't need to prove anything to anyone.

14'SilveradoLT · September 2, 2014

EDIT: I just caught what you were throwing.

This is what Bass Mechanic is referring to I think..

"Almost all vehicles show a pulse width of zero when coasting while in gear. Zero, as in there is no fuel injected at all. Yes, the engine is turning over, the pistons are going up and down, the water pump, alternator and a/c compressor are working, so technically you can say the engine is running, sort of. But it's not consuming any fuel. And that goes for automatic or manuals.

Okay, eventually, at the bottom of the hill or as you creep up to the traffic light, the engine finally will slow to idle rpm—at which point the fuel injection will wake up and start adding fuel to keep the engine from stalling. That usually starts at around 1000 rpm, and if you pay attention, you can sense when it's happening as the engine will rev up slightly. And that's when the scan tool or oscilloscope will show injector dwell rise from 0 to 5 to 10 percent. So you're actually wasting gas by putting your car into neutral." ----http://www.popularmechanics.com/cars/alternative-fuel/news/coasting-in-neutral-fuel-economy

Edited September 2, 2014 by 14'SilveradoLT

14SLTZ71 · September 2, 2014

GM is not going to share their technology with anyone. the bottom line is that i know what i am talking about! every manufacturer does it, it's a common practice. my tacoma used to go to fuel cutoff at 1700 rpm and higher. the GM seems to be cutting fuel around 1,000 rpm.

just keep in mind the engine doesn't have to be "running" it can still be "spinning" and not using any fuel.

look at it this way.. an engine when running is simply spinning things. its turning the alternator, water pump and all the other accessories on the front, and turning the gears and drivetrain at the back.

when your coasting down a hill everything is still turning and that never changes.

but it shouldn't be too hard to believe it is possible to cut the fuel when the vehicle is spinning the engine faster than the combustion process is at idle.

when this happens, they turn off the fuel. why would you need to continue to add fuel to an engine that the driver is commanding 0 torque from?

seems pretty obvious to me.

you can choose to believe it, or not.. doesn't affect my life any! just trying to share some common knowledge with you. you can call me out if you want, and i don't need to prove anything to anyone.

Once again, I didn't say I agree or disagree, I am merely stating that you can't go around saying that's not true to people and then not providing documentation to back it up. If you don't want to provide reputable documentation just quit saying "that's not true" because it's ....................

scott19677 · September 3, 2014

I can'not quote exactly what I was told about how the fuel is cut. The dealer General manager explained this to me over a year ago when I bought my first 2014 and went round and round about the smoking at start up. But 14LTZZ71 is pretty close about the fuel cut off. Maybee Im a Dinosaur but if you think that AFM is going to save the Planet, Guess again. AFM good for longevity of engines? yeah right!. Do you really think these 'FREE' oil changes for the first two years are for our benefit or GMs? Its a race to the bottom for that HolyGrail of one more MPG than the other guy. At the very least AFM should be selectable. AFM is just more of the Govt. sticking their MPG nose in where it doesn't belong. GM knows it sucks, but they probably allocated millions to making it work to save half a gallon per mile just so the Socialist arm of the EPA and the Annointed One himself will allow V8s to exist. I'll put my right foot up against V4 any day of the week. And if you think AFM is seamless, just drive in M5 for a week. Then switch back. I would LOVE to tune it out. But seeing how many issues these 14s are having. I'll have to pass.

WANT A FOUR BANGER , BUY FORD.

The V V T is where GM can really show advancements. Between V V T and cylinder head design and cam grinds. That is where the benefits are. Think about it ,

11.5 to 1 compression ratio on pump gas! And you want to run on 'ALL FOUR'. Well there is always a PRIUS with your name on it.

Edited September 3, 2014 by scott19677

Higgs Boson · October 14, 2014

Deceleration Fuel Cutoff has been a part of GM's fuel strategy for at least 15 years....since the late 90s. I don't remember the first tune I saw it in but 0% throttle definitely means no fuel injector activity until it drops below around 1100 RPM and it kicks back in for idle.

mdmischief · October 28, 2014

Once again, I didn't say I agree or disagree, I am merely stating that you can't go around saying that's not true to people and then not providing documentation to back it up. If you don't want to provide reputable documentation just quit saying "that's not true" because it's ....................

We're all going to say that "it's not true" because it's well known fact that can be found anywhere. DFCO removes all fuel.

Nargg · October 29, 2014

Mine is similar to Danial. 5.3 4x4 also

I dont understand why they didn't have idle at v4.

At idle, they'd actually have to burn more gas in V4 mode to overcome the negative inertia needed to keep the engine running.

V4 mode actually works by using the momentum of the vehicle as it rolls to keep the engine moving as much as burning gas.

I've got a 5.3 2015. Traded in a 2011 5.3 I'm amazed at how much more the V4 mode kicks in compared to my older truck. Much more. Even as I press the gas just a little bit, it still stays in V4. I'm also getting almost 3 MPG better in town than I did with the 2011 5.3...

Also, in regard to the gas comments before I've always burned 89 octane or better in my 5.3s Even the 5.3 non V4 mode version I had before the 2011. These just run better on anything higher than 87 octane. At least with the E15 fuels, with pure gas it does fine on 87 octane.

Oh, and to the doubters, yes, V4 does save gas. http://www.rangetechnology.com/pages/v4 If you want a "muscle truck" then you are obviously not interested in saving gas, so why even go there to argue against V4? You don't need it anyway.

Edited October 29, 2014 by Nargg

stevencox93 · November 7, 2014

I got a question. I see a lot of guys wanting to disable their V4 mode when they get a tune. I read that the old style of motor had issues with the AFM burning oil but haven't read any of these new models doing it or have I missed it? Please if you can explain why you are or are not disabling the V4 mode

KARNUT · November 7, 2014

I got a question. I see a lot of guys wanting to disable their V4 mode when they get a tune. I read that the old style of motor had issues with the AFM burning oil but haven't read any of these new models doing it or have I missed it? Please if you can explain why you are or are not disabling the V4 mode

Most people when they mod the exhaust don't like the v4 sound, so they turn it off. I picked up a slight vibration along with the V4 sound so I turned it off. I had neither when the exhaust was stock. I think by now they fix the V4 oil burning problem. Edited November 7, 2014 by KARNUT