Switching Between V8 And V4?

ALEXANDERJASON · July 4, 2008

i have an 08 vmax 4x4. it seems that even when i am on level ground and cruising on the highway at any speed, if i touch the throttle at all, it moves back to V8. the only time it is in V4 mode is when i take my foot off and coast or when i am going downhill without much foot in the pedal.

how about you guys...??

i would have thought that this feature would be more useful and save some gas more than it does. i am averaging 13 MPG...

hubbycap · July 4, 2008

Over 5% throttle will bring up 8 cyls. If it takes over 5% on level road you may be going too fast or have too great of a load. I find if I'm running much over 70mph its pretty hard to keep it in 4cyl. Of course A/C and alternator is a load as well and will be a big factor this hot time of year.

03blackz71 · July 4, 2008

Mine stays in V4 alot when cruising on the freeway and also stays on going up hills. I notice that the GMPP touring exhaust helped extend how long the V4 mode stays on. I average 17 mpg but I have gotten over 20 with my truck a couple of times.

ColoradoSkiCountry · July 4, 2008

Do any of the tuners out there have a way of making the truck stay in 4 Cyl mode longer? I have a feeling my truck would do just fine in 4 cyl mode with some of the driving I do when it switches into 8 Cyl mode.

nbscanuck · July 4, 2008

It all depends on load (hills, wind, hauling something)and throttle position. I drive on a VERY flat section (according to GPS only 5 feet difference over 5 miles) and I very rarely get V4 if I'm over 65MPH, due to wind resistance. I drop back to 60 OR less, I'm on almost always. I've found my foot is better at getting and keeping V4 than cruise control. I see the inclines in the road and very slight increase in speed far enough back and it will keep it. Cruise can't see the hills and only increases speed when it feels the hill, then it has to push harder to keep the speed.

There was a customer tuner on here a while back that made tunes for V4 mode. So it would hold it longer, start sooner and truck would run better in V4 mode. I guess search and yee shall find

BigJayDogg3 · July 4, 2008

It all depends on load (hills, wind, hauling something)and throttle position. I drive on a VERY flat section (according to GPS only 5 feet difference over 5 miles) and I very rarely get V4 if I'm over 65MPH, due to wind resistance. I drop back to 60 OR less, I'm on almost always. I've found my foot is better at getting and keeping V4 than cruise control. I see the inclines in the road and very slight increase in speed far enough back and it will keep it. Cruise can't see the hills and only increases speed when it feels the hill, then it has to push harder to keep the speed.

There was a customer tuner on here a while back that made tunes for V4 mode. So it would hold it longer, start sooner and truck would run better in V4 mode. I guess search and yee shall find

texsrt4

iminaquagmire · July 4, 2008

As stated above, at 6% throttle it goes back to V8 mode. Justin at Blackbear tuned mine to a little bit higher throttle percentage. It holds V4 Longer but I also have 3:42 gears so its not for long until I still have to get into it and get it in V8 again. With some lower gears, I could see tuning being really beneficial in this regard.

strafingmoose · July 4, 2008

Do any of the tuners out there have a way of making the truck stay in 4 Cyl mode longer? I have a feeling my truck would do just fine in 4 cyl mode with some of the driving I do when it switches into 8 Cyl mode.

I think no tuner wants to touch AFM, a bit risky of an operation and a new technology as well.