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Promising better fuel economy for AFM engines, the Range

Zane

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8.1HD/ALLISON Senior Enthusiast

8.1HD/ALLISON

Posted
Posted

Nope. GM actually did a well engineered system and mechanically everything is basically still "moving up and down". The system just shuts the valves for the deactivated cylinders completely and turns off the coil (no spark) and injector (no fuel). That makes those cylinders like an air spring so you don't lose energy pumping air through them (pumping losses). You still have the same mechanical friction and such (actually slightly less since there's no combustion causing side loading). It's a sound basic design (and Chysler has a similar system for their hemi).

 

There's nothing to cause any excessive wear or oil consumption or anything, except the additional moving parts that turn the lifters on and off.

 

 

I was told when I took the GM training on AFM that the coils stay active to keep the spark plug at operating temp. Did they change this?

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Range Technology Enthusiast

Range Technology

Posted
Posted

I was told when I took the GM training on AFM that the coils stay active to keep the spark plug at operating temp. Did they change this?

 

 

Ooops... my bad ... got carried away. They do keep the secondary voltage hot across the plug and trap the exhaust on deactivated cylinders. Sorry 'bout that.

travis73 Enthusiast

travis73

Posted
Posted

This is an intresting product however I think most people who own the AFM engines actually would rather spend a tiny bit more on fuel and have all of their cylinders activated all of the time,this company should make an opposite product that does just that.Myself I would not even consider using the Ranger as I don't like how my truck operates in 4cyl mode,and with me using this truck for work(reading meters)it is very inconvienient to put it in manual mode then select a gear only to get to my next house and have to put it in park again.If there was a product as simple to install as the Ranger that did not change the factory programing and would allow me to run my truck in 8cyl mode all the time I would be all over it.just my 2 cents worth.

NitroMusky Enthusiast

NitroMusky

Posted
Posted

It does feel like the truck comes out of 4cyl mod at the slightest tip of the pedal and that it can probably handle staying in 4cyl mode under slightly greater load (power-wise at least).

 

That said...for all the engineering and testing that GM has done on AFM to get it right in light of the 8-6-4 debacle, and coupled with GM's need to squeeze every last drop of MPG for CAFE mandates (afterall, that's the reason they did it right?), a key unanswered question remains in my mind:

 

Why wouldn't GM have programmed the AFM system along the lines of the Range in the first place?

 

I understand that these trucks are subject to widely varied weight loads etc, and I guess the 'lowest common denominator' factor could play a part but I haven't seen any caveats to where/when the Range can be used that would support this theory. So what is the real reason? Am I missing something here?

Tucker Enthusiast

Tucker

Posted
Posted

X2 Exactly what I would be interested in as well.I just want to turn off the AFM.

Zane Senior Enthusiast

Zane

Posted
  • Author
Posted

So any test done yet ?

 

Still working our way through the first tank since installing.

Josh Senior Enthusiast

Josh

Posted
Posted

lol

So it seems to work!?

 

so long

j-ten-ner

 

 

Yes, it's very noticeable. The truck goes into 4 cylinder mode and stays there for a lot longer. We are waiting to see what kind of mpg increases we see, if any, until we have put a tank or two through the truck. However, it's hard to believe with it staying in 4 cylinder operation for so much longer, that it wouldn't help somehow.

  • 3 weeks later...
bluArrow Enthusiast

bluArrow

Posted
Posted

No updates for over two weeks. Hmmmmmmmmmmmm........

 

it's hard to believe with it staying in 4 cylinder operation for so much longer, that it wouldn't help somehow.
I've been watching this product because I'm intrigued by the possibilities. Frequently my truck slips into AFM and gets 21 mpg running on four cylinders, the same 21 mpg it was getting in V8 mode. So although I'm only running four cylinders I'm not saving anything as those cylinders are working harder.

 

Now add to this a conversation Car & Driver had with the 2014 Corvette Design team in the March 2013 issue on page 40:

 

Did you consider other engines?
referring to a 5.5L or smaller which was widely speculated on in the media.

 

They replied:

 

A big factor is AFM. If we went to the smaller 5.0L V8 we looked at, we don't get enough torque in the 2.5L four cylinder mode to stay in that mode very long. It's kind of counter intuitive, but the 6.2L, running as a 3.1L four can be in that mode a lot longer, so it returns better fuel economy.

 

 

So if a 2014 Corvette with it's super slippery Cd needs a 6.2L in order to maintain steady AFM what chance does the 5.3L motor stand in my block shaped Sierra?

 

 

(Love the new Corvette by the way)

Morgan1986 Senior Enthusiast

Morgan1986

Posted
Posted

No updates for over two weeks. Hmmmmmmmmmmmm........

 

I've been watching this product because I'm intrigued by the possibilities. Frequently my truck slips into AFM and gets 21 mpg running on four cylinders, the same 21 mpg it was getting in V8 mode. So although I'm only running four cylinders I'm not saving anything as those cylinders are working harder.

 

Now add to this a conversation Car & Driver had with the 2014 Corvette Design team in the March 2013 issue on page 40:

 

referring to a 5.5L or smaller which was widely speculated on in the media.

 

They replied:

 

 

 

 

So if a 2014 Corvette with it's super slippery Cd needs a 6.2L in order to maintain steady AFM what chance does the 5.3L motor stand in my block shaped Sierra?

 

 

(Love the new Corvette by the way)

 

dont know how the new 4.3l will hold in afm then.
Range Technology Enthusiast

Range Technology

Posted
Posted

[

No updates for over two weeks. Hmmmmmmmmmmmm........

 

Nothing really to update from our end. Pretty much just listening to the discussion. BTW, we heard you about turning the AFM OFF ... we're investigating that actively right now. Too early, but it's looking promising.

 

Frequently my truck slips into AFM and gets 21 mpg running on four cylinders, the same 21 mpg it was getting in V8 mode. So although I'm only running four cylinders I'm not saving anything as those cylinders are working harder.

 

There's a definite sweet spot where the torque/efficiency crosses over between V8 and V4. Don't go by the DIC for MPG. It's an approximation ... we used a very precise fuel flow meter, realtime calculations based on the ECU data and a 5 gas analyzer to get down to the nitty gritty. Fascinating engineering exercise, BTW! :)

 

So if a 2014 Corvette with it's super slippery Cd needs a 6.2L in order to maintain steady AFM what chance does the 5.3L motor stand in my block shaped Sierra?

 

You have to factor in the very high 7th gear overdrive ... it's barely turning over at cruise. That will really affect load too.

 

(Love the new Corvette by the way)

 

 

So do I ... the rear end is going to take some getting used too though. Looks fine in dark colors, but not really a fan of the lower body color insert being black on something like a red or other bright colors. Have to see it in person I guess.

tyhuck Senior Enthusiast

tyhuck

Posted
Posted

Just remember, AFM was developed to increase the average MPG over the entire GM fleet. Fractions of a gallon may not seem like much to an individual, but when you calculate it out over millions of vehicles sold in all classes combined, it helps companies stay within the EPAs regulations.

MikeNH Senior Enthusiast

MikeNH

Posted
Posted

dont know how the new 4.3l will hold in afm then.

 

 

The new 4.3 will likely have 300HP if not a bit more so you can't think if it in terms of the current motor with 110+ less HP.

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