red 1

On a 1300 hundred mile trip I did the first 650 in Reg V4 mode with the A8 it was shifting continuosly and got 29.4 MPG. On the second 650 mile segment I used the Range V4 disabler and got 28.9 MPG, both segments were at 78 to 80 MPH, in my opinion the disabler is the only way to go.

mtaxman

I'm ignorant...what is "the Range V4 disabler"? Also, was the route relatively flat or relatively hilly?

CP

https://www.rangetechnology.com/prod...V8?add=Buy+now


Really need some BIG MPG differences to break even on the $200 cost. Why use something that causes you to LOSE mpg as in your example?

mtaxman

he got worse mileage...he will never make money with whatever that is...I think his point was the shifting was annoying?

Foosh

One of the advantages of the M7 is that it only goes to V4 when "economy" mode is selected. I can see using it on a long, flat, interstate road trip, but haven't tried it yet.

4thC4at60

In normal highway driving I get from 28.7 to 33.1 mpg - in normal V8 operation. Why in the world would I buy a performance V8 car and run it in V4 mode? I don't get it....

Recently, I set the cruise on 90 mph on Texas SH130 (legal speed limit 85 mph) and I averaged 27.xx mpg .....

V4 mode? Not for me....

Foosh

I guess for the same reason you'd buy a high performance V8 and run it at 1500 rpms. What difference does it make when you're on an interstate in 7th or 8th gear with cruise control set at 75 mph?

Widgeon5

Not for me either. I'm not an engineer, but I speculate that the temperature cycling in the deactivated cylinders will impact engine longevity. I tried it once to see if it worked, will likely never use it again. Easy to avoid with my M7.

gve

For engine longevity you do not want it continually going from Firing on 8 cyl to 4 cyl. When I picked it up from the museum they told me to keep the A8 in manual so it would fire on all 8 cyl during the 500 mile break in.
It's not the best for the rings and Pistons in the 4 cylinders to not be under compression. These engines tend to use more oil after about 40,000 miles.
Google AFM (active fuel management) and GM engines problems you will find plenty of evidence of this. In fact my 2013 Avalance with 50,000 miles started using oil and had to have new rings and Pistons installed, I was lucky that it was still under warranty. You can sometime feel the engine vibrate as its going back to 8 cyl if you give it light throttle I put the Range AFM eliminator on the Avalanche after the rebuild and I also put one on my 2016 ZO6. If you aren't going to keep the car to that mileage then it's probably not worth doing anything.

Here is one article.
http://www.tundraheadquarters.com/bl...l-consumption/

SCB

Well, it's kind of like saying, "I bought a 25,000 BTU air conditioner, and I want to use all of them all the time".

There's really no need to be firing on all 8 cylinders all the time. Cruising at a steady 65 mph only requires around 20 hp out of the 460 available.

When you get on the accelerator, it goes into V8 mode pretty instantaneously. The transitions between V4 and V8 mode are pretty seamless. at least on mine.

X25

+1; I would not want to have it on my car if I had the choice (to remove the weight, complexity, etc.), but since I have it, why not use it? It adds 5+ MPG on constant speed cruises on the highway with my M7, and I also love playing with throttle and gears (choosing 6th or 7th; 7th is not always the best choice) to find the optimum fuel economy on the highway. I have to say, though, it's not as smooth on the manual cars.

air86

Sometimes mine clunks real hard going from v8 to v4 and vice versa. I need to have an oil change done. Maybe I will have them take a look while its there.

stevettec7

GM deems the engine shudder as normal operation during AFM activation😏 Garbage!

MAKC7

After driving at Spring Mountain, I use the manual (A8) mode 100% of the time with no tranny issues. Didn't buy my Z51 for high gas mileage.

kitesurfer

i've got under 400 miles on my 2 week old stingray. how do i tell when it's in 4 cylinders? can i keep it from going to 4 cyl? i have A8. thanks.

Fastoldguy

Nope, I don't Get It. I'm still trying to Love my C7 but there's some things I Just Don't Like. My C6 ran like a Champ and got 26 mpg mixed mileage. My C7 does the V8-V4 Crap and gets about the same mileage. I have also considered getting a "widget" to keep it in the V8 mode. I don't like the seats either and it doesn't ride as good as my C6.

dodgersphc

Got to do this exact thing last year, works really well, averaged 30+mpg for a 500 mile trip. With the almost daily postings of A8 problems, combined with control of the engine going into V4, I'm really happy I went with M7.

Ernest_T

Version D of that PIP is out.

stevettec7

Please share that new version.

ovrebo1

Engineers and people that don't turn wrenches think the DOD/AFM is great.

As a mechanic I think its a horrible idea for a small gain that just ends up doing more long term damage. I was watching a video about the factory and Tadge explained how the torque tube had to be strengthened to withstand all the vibrations caused by running in V4 mode.......how does that in any way sound like DOD/AFM is a good concept?