V4 Mode
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Joined: Jul 2014
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V4 Mode
I was sitting on the interstate the other day for several hours. I noticed two things.
1. After idling for about an hour the engine shut off. It started back up without any issues. Was it designed to shut down like that?
2. You would think that while idling the car would go into the V4 mode. This things love fuel while sitting still.
Thanks
1. After idling for about an hour the engine shut off. It started back up without any issues. Was it designed to shut down like that?
2. You would think that while idling the car would go into the V4 mode. This things love fuel while sitting still.
Thanks
Drifting
Joined: Jun 2007
Posts: 1,425
Likes: 238
From: Macomb MI
I was sitting on the interstate the other day for several hours. I noticed two things.
1. After idling for about an hour the engine shut off. It started back up without any issues. Was it designed to shut down like that?
2. You would think that while idling the car would go into the V4 mode. This things love fuel while sitting still.
Thanks
1. After idling for about an hour the engine shut off. It started back up without any issues. Was it designed to shut down like that?
2. You would think that while idling the car would go into the V4 mode. This things love fuel while sitting still.
Thanks
#2) V4 mode sounds like a$$ (even when baffled with the valves) and is a bit unstable at idle RPM. People expect to hear a V8 out of an idling Corvette. The car cant differentiate between idling on a freeway (where no one would care) and stoplights, car shows, garages, parking lots, etc. (where people would care).
EDIT: Glen's answer to #2 is better
Last edited by xp800; Nov 30, 2015 at 04:26 PM. Reason: Glen e is better answer to #2
Melting Slicks
Joined: Nov 2013
Posts: 2,016
Likes: 73
From: Texas
Race Director
Joined: Sep 2013
Posts: 11,825
Likes: 2,473
From: Ft Lauderdale
Tech Contributor
True, but that's still rolling… From a dead stop you use a tremendous amount of HP just from 0 to 5....
Drifting
Joined: Aug 2015
Posts: 1,434
Likes: 183
From: Maple Ontario
I suspect it would be a rough idle if in 4 cylinder mode when stopped... but it might be preferrable to stop/start technology... GM can rig it as follows...
1: if in Eco mode, and idling for more than 1 minute, got to 4 cylinder mode. Then as soon as your off the brake and on the accelerator pedal, go to V8 mode. Is suppose that they can tune it to avoid possible gas guzzler taxes in the FUTURE, should CAFE requirements further put a strain on their ability to meet any tighter standards... this would also require that Eco mode be the default. Alot of us might not like that, and perhaps there can be a back door to override it... but tighter CAFE standards may force GM's hand...
2: in any other mode, stay in V8 mode
1: if in Eco mode, and idling for more than 1 minute, got to 4 cylinder mode. Then as soon as your off the brake and on the accelerator pedal, go to V8 mode. Is suppose that they can tune it to avoid possible gas guzzler taxes in the FUTURE, should CAFE requirements further put a strain on their ability to meet any tighter standards... this would also require that Eco mode be the default. Alot of us might not like that, and perhaps there can be a back door to override it... but tighter CAFE standards may force GM's hand...
2: in any other mode, stay in V8 mode
Melting Slicks
Joined: Nov 2013
Posts: 2,016
Likes: 73
From: Texas
Certainly agree with you, I'd have never suggested the V4 mode would work well from a stop. I'd like to see if my car could make it to 100 on V4 like Tadge said they could. Would have to be very gentle with the throttle if that could happen. Don
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Instructor
Joined: Nov 2015
Posts: 236
Likes: 50
Whats the difference? As soon as you touch the throttle it could simply switch to V8 mode.
But honestly I notice very little difference in fuel economy between V4 and V8 mode. Only about 2-3 MPG. Which I know in the car world is huge. But I don't care about 2-3 MPG personally.
Melting Slicks
Joined: Dec 2005
Posts: 2,017
Likes: 169
From: SE VA VA
On my last road trip, the difference between eco and track was about 1.5 mpg. Typical speed was in the mid 80's though
In typical DD usage, I hardly ever make it past 3rd gear, so V4 doesn't kick in.
Even so, gets better mileage than my other vehicles.
Intermediate
Joined: Sep 2007
Posts: 47
Likes: 1
From: Coral Springs FL
I noticed the same thing this past weekend traveling across Alligator Alley which is 75 miles of smooth and straight road. I had the cruise set at 79mph and put it in eco mode. I decided to put it back in sport mode to see the difference in mileage and it didn't seem to make a difference, if anything it was 1 mpg higher in sport mode. I have a 2016 M7 Z51.
Instructor
Joined: Nov 2015
Posts: 236
Likes: 50
I noticed the same thing this past weekend traveling across Alligator Alley which is 75 miles of smooth and straight road. I had the cruise set at 79mph and put it in eco mode. I decided to put it back in sport mode to see the difference in mileage and it didn't seem to make a difference, if anything it was 1 mpg higher in sport mode. I have a 2016 M7 Z51.
I'll be on the lookout for a Red C7!
Drifting
Joined: Sep 2012
Posts: 1,443
Likes: 116
From: No Longer in CA! NV
Can't do that in V8 mode.
Drifting
Joined: Oct 2011
Posts: 1,298
Likes: 77
From: Wichita Kansas
I was sitting on the interstate the other day for several hours. I noticed two things.
1. After idling for about an hour the engine shut off. It started back up without any issues. Was it designed to shut down like that?
2. You would think that while idling the car would go into the V4 mode. This things love fuel while sitting still.
Thanks
1. After idling for about an hour the engine shut off. It started back up without any issues. Was it designed to shut down like that?
2. You would think that while idling the car would go into the V4 mode. This things love fuel while sitting still.
Thanks
Safety Car
Joined: Jan 2015
Posts: 3,941
Likes: 499
From: Northern Virginia
To idle in 4 cyl mode the ECU would have to increase idle speed substantially. Notice that most 4 bangers idle around 1000-1200 rpm. The LT1 idles around 600. At that rpm with only 4 cylinders firing idle would be very rough.
It could certainly be done, but I wonder how the faster idle would affect fuel used compared to the slower idle and 8 cylinders.
If fuel savings while stopped is the goal, a start-stop system is far more effective anyway. I bet we'll see it in 2017.
It could certainly be done, but I wonder how the faster idle would affect fuel used compared to the slower idle and 8 cylinders.
If fuel savings while stopped is the goal, a start-stop system is far more effective anyway. I bet we'll see it in 2017.
Instructor
Joined: Nov 2015
Posts: 236
Likes: 50
To idle in 4 cyl mode the ECU would have to increase idle speed substantially. Notice that most 4 bangers idle around 1000-1200 rpm. The LT1 idles around 600. At that rpm with only 4 cylinders firing idle would be very rough.
It could certainly be done, but I wonder how the faster idle would affect fuel used compared to the slower idle and 8 cylinders.
If fuel savings while stopped is the goal, a start-stop system is far more effective anyway. I bet we'll see it in 2017.
It could certainly be done, but I wonder how the faster idle would affect fuel used compared to the slower idle and 8 cylinders.
If fuel savings while stopped is the goal, a start-stop system is far more effective anyway. I bet we'll see it in 2017.
Safety Car
Joined: Mar 2009
Posts: 4,101
Likes: 719
From: Northeast MA & Mad Beach FL
When I got my 2016 I noticed a shuttering 90% of the time coming from somewhere.
Never gave the V8/V4 thing a thought until I watched it in the DIC and noticed it spent a lot of time in V4 unless I was actually on the throttle.
I also noticed it did Not instantly go from V4 to V8 when I gave it a little throttle to accelerate a bit like when driving around town.
I lived with it for abut 400 miles and then bought a Range AFM Disabler.
Plugs into the OBDII port and doesn't change the tune but keeps it in V8 100% of the time.
Car is much more enjoyable to drive now and glad I did it.
YMMV
Never gave the V8/V4 thing a thought until I watched it in the DIC and noticed it spent a lot of time in V4 unless I was actually on the throttle.
I also noticed it did Not instantly go from V4 to V8 when I gave it a little throttle to accelerate a bit like when driving around town.
I lived with it for abut 400 miles and then bought a Range AFM Disabler.
Plugs into the OBDII port and doesn't change the tune but keeps it in V8 100% of the time.
Car is much more enjoyable to drive now and glad I did it.
YMMV