V4 mode
Thread Starter
Cruising
Joined: Jan 2012
Posts: 11
Likes: 1
From: Huntington Beach CA
V4 mode
I have a 2017 Stingray, M7. I am curious about the effect of v4 mode on the engine. When I am in Economy mode, there is sometimes what I would characterize as a bump when the engine switches from v8 mode to v4 mode. What is happening when it does this? It there some mechanical movement, such as the cam shaft? Also, when in v4 mode, does the engine always run on the same set of 4 cylinders, or does it use all 8, but only 4 at a time? Is there any harm in using v4 mode?
Moderator emeritus
Joined: Jun 2001
Posts: 18,599
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From: Jacksonville Florida BWO Dayton, Cincinnati, Bloomsbury NJ, Cincinnati
2015 C7 of the Year Finalist
Active Fuel Management (AFM), which shuts down the LT1’s firing cylinders from eight to four by disabling the valves to the cylinders. When AFM initiates, the engine turns the 6.2L V8 into a 3.1L V4, shutting down cylinders 1, 4, 6 and 7, and firing only cylinders 8, 2, 5 and 3 in that order.
Otherwise, the complete firing order is 1, 8, 7, 2, 6, 5, 4, 3.
2, 4, 6, 8, Passenger side from front to rear.
1, 3, 5, 7, Driver's side from front to rear
Elmer
Otherwise, the complete firing order is 1, 8, 7, 2, 6, 5, 4, 3.
2, 4, 6, 8, Passenger side from front to rear.
1, 3, 5, 7, Driver's side from front to rear
Elmer
Le Mans Master
Joined: Jun 2002
Posts: 6,426
Likes: 3,610
From: Commerce Texas
I found the lurch up and down to be so annoying that my first time going into V4 was my last - 79,000 miles and averaging more than 30 mpg for the entire 79,000 miles... why would I go back to V4? To gain another 3 MPG? Four?
Last edited by 4thC4at60; Dec 8, 2018 at 12:21 PM.
Drifting
Joined: Oct 2014
Posts: 1,733
Likes: 403
From: Atlanta, GA
I have an M7. I kinda think of the bump going from V4 to V8 is like an afterburner lighting off. 
I do use it but only on long trips and level roads. I also notice that if I cruise in 5th instead of 6th (60-70mph)..theres more available torque even in V4 in 5th to prevent as much switching. 5th in V4 will give a little better MPGs than V8 6th gear.
But honestly....it'd be hard to REALLY notice the difference unless you're doing long drives in E. I'm only in E on long trips...otherwise it's T S or W given the conditions.
Drive on....
I do use it but only on long trips and level roads. I also notice that if I cruise in 5th instead of 6th (60-70mph)..theres more available torque even in V4 in 5th to prevent as much switching. 5th in V4 will give a little better MPGs than V8 6th gear.
But honestly....it'd be hard to REALLY notice the difference unless you're doing long drives in E. I'm only in E on long trips...otherwise it's T S or W given the conditions.
Drive on....
Instructor
Joined: Oct 2014
Posts: 151
Likes: 13
From: West Hartford Connecticut
Active Fuel Management (AFM), which shuts down the LT1’s firing cylinders from eight to four by disabling the valves to the cylinders. When AFM initiates, the engine turns the 6.2L V8 into a 3.1L V4, shutting down cylinders 1, 4, 6 and 7, and firing only cylinders 8, 2, 5 and 3 in that order.
Otherwise, the complete firing order is 1, 8, 7, 2, 6, 5, 4, 3.
2, 4, 6, 8, Passenger side from front to rear.
1, 3, 5, 7, Driver's side from front to rear
Elmer
Otherwise, the complete firing order is 1, 8, 7, 2, 6, 5, 4, 3.
2, 4, 6, 8, Passenger side from front to rear.
1, 3, 5, 7, Driver's side from front to rear
Elmer
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Drifting
Joined: Mar 2013
Posts: 1,705
Likes: 538
From: Hampton VA
I have a M7 and have never put the car in eco and never will for goodness sake its a Corvette not a Spark you want mpg buy the spark. If you set the car for sport tour or track it wont go into V4 with the M7 . 
Safety Car
Joined: Mar 2009
Posts: 4,101
Likes: 719
From: Northeast MA & Mad Beach FL
Most notable is reduced Throttle response.
Not that it cannot be defeated with heavy throttle, but it definitely makes it a lot harder to lose control.
I use it in the rain or wet roads, and don't really notice the reduced throttle.
Just to see how well it works, I tried a few times and it takes a lot more to get tire spin or the rear end to kick out.
The car is definitely more stable in Weather mode and I really like it when needed
Safety Car
Joined: Dec 2009
Posts: 4,194
Likes: 305
From: Lake Havasu City Arizona
SoCal Events Coordinator
St. Jude Donor '12
My M7 will never be in Eco mode. I did not buy this thing for it to sound like a rice burner. Lucky for M7 owners the manual trans car will not go into V4 unless the car is in eco mode. Autos will go into V4 in all modes unless you put the shifter into M.
Drifting
Joined: Oct 2014
Posts: 1,733
Likes: 403
From: Atlanta, GA
In Weather mode all the nannies are more sensitive and intervene a lot sooner than the other modes.
Most notable is reduced Throttle response.
Not that it cannot be defeated with heavy throttle, but it definitely makes it a lot harder to lose control.
I use it in the rain or wet roads, and don't really notice the reduced throttle.
Just to see how well it works, I tried a few times and it takes a lot more to get tire spin or the rear end to kick out.
The car is definitely more stable in Weather mode and I really like it when needed
Most notable is reduced Throttle response.
Not that it cannot be defeated with heavy throttle, but it definitely makes it a lot harder to lose control.
I use it in the rain or wet roads, and don't really notice the reduced throttle.
Just to see how well it works, I tried a few times and it takes a lot more to get tire spin or the rear end to kick out.
The car is definitely more stable in Weather mode and I really like it when needed
Melting Slicks
Joined: Dec 2017
Posts: 2,012
Likes: 955
From: Central Commiefornia
Drifting
Joined: Aug 2005
Posts: 1,314
Likes: 817
From: Melbourne FL
I tried eco mode on my M7 for the first time on a trip last month. Averaged 28.5 mpg in V8 on the way up. On the way back, I put it in eco and averaged 29 mpg. It went in and out of V4 smoothly, but it's not worth it for 0.5 mpg.
Melting Slicks
Joined: Dec 2004
Posts: 3,244
Likes: 562
From: Margaritaville Daytona
It also keeps the car from yawing more than about 30 degrees when skidding under power.
Spring Mountain has a great demo of how it works https://www.youtube.com/watch?v=BX72yQO0CEs
Spring Mountain has a great demo of how it works https://www.youtube.com/watch?v=BX72yQO0CEs
Last edited by AmmoVet; Dec 9, 2018 at 12:02 AM.