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Been reading every post on the A8 issues and there was never a doubt that I would get the M7 but does the M7 ever go into V4 mode when NOT in Eco mode?
I had heard that at times in high gear that even the M7 would or could go into V4 mode and want to prevent that from happening.
Do not want to beat a dead horse by discussing what some stickys and threads are already covering but trying to ascertain if an M7 out of Eco mode will completely stop V4 from engaging.
This can be confirmed by watching the fuel economy display - it has a little green "V4" icon that lights up when in V4 mode. When the car is in V8 mode its says "V8" in yellow. You can hear and feel the change too, its subtle at first but once you experience it a few times you'll start to pick up on it.
I found this picture online (not mine) of the display... this is an automatic (in "D" = drive) showing Tour mode and V4 at the same time (cruise control is on as well):
Thanks for the info.
I was looking for correct information from those who us the M7. . I did not want to walk through the same potential minefield that the A8 LT1 owners are experiencing.
Thanks for the info.
I was looking for correct information from those who us the M7. . I did not want to walk through the same potential minefield that the A8 LT1 owners are experiencing.
this is what i did. i was all set to get the A8 as its pretty amazing UNTIL i came across all the problems. the problems are known and have a fix but i still didnt want anything to do with it.
the M7 will NOT go into V4 mode period, unless the mode selector is in eco. furthermore, in eco mode itll go into V4 regardless of what gear youre in, top gear isnt needed. hell, itll do it in fourth if youre just putzing along.
only thing i dont like about the whole thing is that you cant make rev match stay on. when starting the car, its off by default and you have to remember to turn it on.. after a couple mins when the engine is warm =]
Phalse,
Thanks. Remembering to always select Eco when you start up is a no brainer as I do it with my wife's MB. After a while, you do it without thinking like pushing in the clutch..
I just picked up my Corvette Z51/M7 a week ago, and we drove 800 miles over three days to get home. Most of the time on the freeway was spent in eco mode, and you can feel a tiny stutter when it goes to V4 mode, along with a subtle change to the exhaust note, which becomes deeper, like shifting up another gear. As you apply throttle (like going up a modest grade on the hilly Kentucky interstate), it returns to V8 mode, you again feel a subtle change, and the engine changes its tone. Other than that, I did not notice any other clues. The car got 27.6 MPG on average over three or four hundred miles, as we wound our way from Tennessee and north into Michigan. Any use of the throttle seemed to cause it to instantly drop out of V4 operation, and I did not observe any V4 operation in any of the other driving modes.
Maybe its just me but I still pulled almost 30 mpg in V8 mode on a long drive. I'm not a fan of the cylinders going on/off/on/off the entire time in ECO mode. I used ECO mode once, didn't notice a huge MPG difference, turned it off and never touched it again nor will I (unless something crazy happens like I need gas ASAP).
Tycho,
I think you are indeed brave by keeping it in Eco mode. From what I know it appears most of the issues associated with V4 mode have been with the torque converters in A8 cars. However, maybe because I'm old school but I think going from 8 to 4 cylinders is a recipe for trouble. I do not know of any M7's that have given issue and know they are a smaller percentage of what is on the road but why temp faith for a very nominal gain. Will be interesting to see if GM stays with this LT1 in the C8...
I hear you there. However I didn't think the M7 was going to be any problem with AFM. If it's going to goof up, It's probably good for it to goof up now, though, since the extended warranty runs out in a couple months. As I get to know this car, I will be trying to track mileage in both Eco and Tour mode to see if there's any measurable difference from V4/V8 or straight-up V8 driving mode. I may eventually change to a more aggressive cam, but not until I know the whole powertrain functions and can assess the ramifications of disabling the AFM and limiting VVT to 20-something degrees. However, I am delighted to have seen high 20's. The car reported 27.4 MPG, and mileage to fuel-fillup put it at 27.6, so the car's fuel consumption calibration seems to be quite accurate.
Running Eco mode during my Z51 M7 drive home (NJ to FL = 1,207 miles) I managed 28.2 MPG while averaging 62 MPH per the computer. Pretty impressive. During one stretch I managed 33.0 MPG with the average at 52 MPH. Doing the math based on fill ups myself I've found the computer is about 1 MPG optimistic. I keep a spreadsheet of this stuff... mostly for maintenance and consumables as it can provide some entertaining numbers. For example I get around 7 MPG on track.
Tycho,
Good luck with your endeavor. Will be interesting to track your progress and others who use the Eco function on the M7 to observe any long term issues.
Once out of warranty you can tune the Eco mode out if you choose. I think I would. Would also be interesting to see if there would be any issues with the A8 cars if the cylinder deactivation was tuned out. That way you could see if the TC was actually the issue or a combination of the AFM and the TC they use...
Tycho,
I think you are indeed brave by keeping it in Eco mode. From what I know it appears most of the issues associated with V4 mode have been with the torque converters in A8 cars. However, maybe because I'm old school but I think going from 8 to 4 cylinders is a recipe for trouble. I do not know of any M7's that have given issue and know they are a smaller percentage of what is on the road but why temp faith for a very nominal gain. Will be interesting to see if GM stays with this LT1 in the C8...
Only had 1 issue with AFM in my '14 Z51 M7 and that was the very first time I tried ECO mode, with maybe 1000 miles on the car. Car shuddered and shaked and threw the infamous differential error in the DIC. I had it checked by dealer and nothing was found wrong. Never had a problem after that 'till the day I sold it with 52K on the clock. And I did keep it in ECO mode most of the highway time
I think once would be enough. Obviously, the car did not like going in Eco mode at least on that one event.
Personally, As long as a performance car will return 25 mpg I am good....
I think once would be enough. Obviously, the car did not like going in Eco mode at least on that one event.
Personally, As long as a performance car will return 25 mpg I am good....
We chalked it up to a solenoid sticking. That first time must have freed it up!
Thank god we have the option in the M7s through ECO to selectively not ever engage the mode. 9000 miles in my Z and it’s never seen ECO. While rare there have been documented cases of valvetrain collapse when selecting the mode.
Joe,
I have always wondered why the A8 did not get the choice. I know many folks, me included, who would pass if I did not have the option to opt out of ECO mode..
It would seem that GM would have saved a lot of money in warranty work on the A8's if they did not go into V4 mode..
03-05-2019, 09:51 AM
Clarification on M7 and going into V4 mode
NEVER have, never will. 
