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Question about V4 mode


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I know I'm way behind the curve here, but I just switched from  a 2005 Silverado to a 2017 Sierra and have been reading up a little to learn about my new ride.  I have seen a lot about this AFM or V4 mode jazz which is all new to me until now.  I have looked for an answer to the question..Is it on ALL GM trucks?  I watched some videos on youtube pertaining to the cat back exhaust systems and these trucks.  The ones I've seen showed a Manual position on the shifter quadrant and a small window below the speedo showing v4 or v8.   My sierra is a base model 1500 regular cab 8 ft bed two wheel drive with a 5.3     My shift quadrant has a LOW postion at the bottom and no v4/v8 indicator.  I hope that means I don't have that crap on my truck.  I'm old school and only need me and a gas pedal.  Can any one enlighten me on this?   Thanks for any info.

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I know I'm way behind the curve here, but I just switched from  a 2005 Silverado to a 2017 Sierra and have been reading up a little to learn about my new ride.  I have seen a lot about this AFM or V4 mode jazz which is all new to me until now.  I have looked for an answer to the question..Is it on ALL GM trucks?  I watched some videos on youtube pertaining to the cat back exhaust systems and these trucks.  The ones I've seen showed a Manual position on the shifter quadrant and a small window below the speedo showing v4 or v8.   My sierra is a base model 1500 regular cab 8 ft bed two wheel drive with a 5.3     My shift quadrant has a LOW postion at the bottom and no v4/v8 indicator.  I hope that means I don't have that crap on my truck.  I'm old school and only need me and a gas pedal.  Can any one enlighten me on this?   Thanks for any info.

You have it.


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You have it, tune it and chop the exhaust off and have fun with it, just did headers on my 14 6.2 and i average 15.3 and thats not pussyfooting it either cause i like to hear my exhaust and plenty of people say they dont see a mileage difference when its disabled but you dont want it on if you get an exhaust

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On 8/29/2018 at 3:23 PM, ringbuster said:

 I hope that mea.ns I don't have that crap on my trucI'm old school and only need me and a gas pedal.  Can any one enlighten me on this?   Thanks for any info

Many of us on this forum are "old school" but we still accept improvements.  Shoulder straps and unleaded fuel were criticized when they became mainstream.  The fuel efficiency of your '17 will be a dramatic improvement over your '05 and still deliver more power.  If you can't tell if you have AFM, leave it alone.  I've been driving for the past 10 years with GM AFM and it is unnoticeable.  

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46 minutes ago, Donstar said:
  On ‎8‎/‎29‎/‎2018 at 5:23 PM, ringbuster said:

 I hope that means I don't have that crap on my truck. I'm old school and only need me and a gas pedal.  Can any one enlighten me on this?   Thanks for any info

I don't have the years on my AFM Donstar has but I'm accumulating a fair number of miles. I do like to drive. In 75,000 I can count the number of times I've 'felt' it go into or come out of AFM. I've had zero issues with it. Personally, it's been good for better than a 5% bump in fuel efficiency. Others will opine other and say it doesn't make 1 mpg difference. I would expect these are the same types that get on a review forum for tires and complain "These are the worst tires on earth. I only got 15 K from them" while not telling anyone that the front end is out of alignment and worn out and they never rotate or check pressures. You get out of it what you put into it. 

"For the believer no proof is needed. For the sceptic no proof is possible". 

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I don't have the years on my AFM Donstar has but I'm accumulating a fair number of miles. I do like to drive. In 75,000 I can count the number of times I've 'felt' it go into or come out of AFM. I've had zero issues with it. Personally, it's been good for better than a 5% bump in fuel efficiency. Others will opine other and say it doesn't make 1 mpg difference. I would expect these are the same types that get on a review forum for tires and complain "These are the worst tires on earth. I only got 15 K from them" while not telling anyone that the front end is out of alignment and worn out and they never rotate or check pressures. You get out of it what you put into it. 

"For the believer no proof is needed. For the sceptic no proof is possible". 


I didn’t know you put a tune in your truck to test your cylinder deactivation. I did in the summer of 2014 and posted the results on this website. Mine was at 72 MPH didn’t even make a 1 MPG difference. Maybe it would have at lower speeds, but where I drive the speed limits are 70-75. Oh, like you no complaints on the tires. 5 per cent, we’ll see if that’s worth the extra do-das in and on your engine at say 200K miles. At your rate in maybe 4 years, good luck. Me I didn’t make out so well with the 5.7 diesel or the first 8-6-4 test caddy.


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Let’s say these trucks average 16 mpg.

One group of folks state they notice a 5% improvement in MPG with AFM.
That equates to an improvement of 0.8 mpg.

Another group of folks state they don’t notice even a 1 mpg drop when they disable AFM.

It’s entirely possible that both groups are making accurate statements.


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1 hour ago, KARNUT said:

 I didn’t make out so well with the 5.7 diesel

I loved my 5.7 Diesel, it was in our '82 Olds Cutlass Supreme Brougham!  Miss that car!  Used to deliver pizzas in it and used to bracket race at the drags with it.  If I had kept it longer, I was going to put a 200R4 and a 3.42 gear behind it and "tune" the injector pump for more power.  The Buicks consumed all my attention then and we sold it to our lawn guy.

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I loved my 5.7 Diesel, it was in our '82 Olds Cutlass Supreme Brougham!  Miss that car!  Used to deliver pizzas in it and used to bracket race at the drags with it.  If I had kept it longer, I was going to put a 200R4 and a 3.42 gear behind it and "tune" the injector pump for more power.  The Buicks consumed all my attention then and we sold it to our lawn guy.

We had 4, nightmares. We converted to gas change the torque converter and never looked back.


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6 hours ago, pronstar said:

Why GM thought it was a good idea to build a diesel out of a gasser is anyone’s guess.

That's a common misconception, such was not true.  Time would have improved the design, mine was the ultimate "D" block which racers converted to gas for drag racing.  They were essentially legislated out of existence and their successor was the 6.2 and 6.5 used in trucks which are still used by the military to this day.  That LF9 got 24 mpg delivering pizzas all night (never shut off) and over 35 mpg on the highway.  Most folks killed them with dirty oil and trying to spin the engine into the red all time.  

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