V4 mode not working

[TJay74]

1" will throw you off about 1.7mph at 60, speedo will show 60 you will be doing 58.35 actual. Over the course of 600 miles you will only have done 583.5 miles but the odometer will show 600.

[divicevich]

1" will throw you off about 1.7mph at 60, speedo will show 60 you will be doing 58.35 actual. Over the course of 600 miles you will only have done 583.5 miles but the odometer will show 600.

With that being said can that small change affect the V4 mode?

[TJay74]

I don't know for sure, have not looked at the stock calibration to see what it looks like in regards to how the AFM works,

[ace ventura]

I'm sure Justin from Black bear performance would know. I would email them. They are on this site and I would highly recommend them for a tune.

 

 

http://www.blackbearperformance.com/contact.asp

[KUUG]

With that being said can that small change affect the V4 mode?

 

I made a larger change, I went with 33" tires and different wheels, my truck hasn't hardly been in V4 much at all since. I'm going to fix the speedo but not for a few weeks

It does switch into V4 more at lower speeds now, mostly under 50 mph

[divicevich]

The tires I added are 33" as well. Talked to Hypertech today and will probably order the speed calibrator. As per their instructions I measured my tires from ground up and it was actually 32 1/4". Brother in law has the same truck with the stock tires, gonna measure his just to be sure thats were the problem is. If his measures 32" then the tires are not the culprit. My bet is the stocks will measure around 31"…hopefully.

[TorkFaze]

Anything you do that makes the engine need to make more torque (taller tires, cold weather due to colder oils and more friction, changes to aerodynamics, etc) to get to the same drive force will mean that you can not run V4 as much. Example...5% taller tires means that to make the same drive force at the same speed, the engine needs 5% more torque. If you just correct the speedo for the tire size, it means the engine spins 5% SLOWER for the exact same ground speed, AND needs to make 5% more torque.

 

 

There's a limit to how much torque the engine can make in V4 (half the cylinders, so makes no more than about half the max torque @ the RPM you're running) and that amount WILL change with fuel quality (summer/winter, etc). If you need more than the engine is capable of in V4 because of any of these things (or many more), you'll see less AFM time. If you were on the ragged edge of being able to run V4 before the tire change, the lower RPM and higher torque required will be enough to put you in a condition where V4 won't be able to provide the torque you're asking for with your right foot.

 

All of this typically is more noticible at higher (i.e. highway) speeds when it takes more torque to push the truck through the air than at lower speeds.

 

Hope this helps.

[KUUG]

The tires I added are 33" as well. Talked to Hypertech today and will probably order the speed calibrator. As per their instructions I measured my tires from ground up and it was actually 32 1/4". Brother in law has the same truck with the stock tires, gonna measure his just to be sure thats were the problem is. If his measures 32" then the tires are not the culprit. My bet is the stocks will measure around 31"…hopefully.

 

Let us know your results

[divicevich]

Stock tires did measure 31" so its a 1 1/4" difference. TorkFaze if I understand you correctly the speedometer calibrator really won't change the performance it will just do as its name says and calibrate the speedometer and mileage correctly. They claim it will change shift points and improve the mileage I'm currently getting, true?

 

On another note, yesterday while driving down wind, flat hwy cruise set at 61mph V4 mode getting 20-21mpg, from time to time V8 would kick in and I was getting 23-24 mpg…what gives?

 

Also had a well known company that does custom tunes tell me that they can help with mileage and shifting since I added the larger tires but that the AFM is really just a gimmick.

[TJay74]

I wouldn't say AFM is a gimmick, it just is not aggressive enough to really make a difference. Even in V8 mode my 6.2 is showing 20-23 on the highway at times.

[DanielAcosta]

The speedometer calibrator will affect your shift points and AFM, at least it did for me as previously posted. Example: if your speedo says 41 but you're really doing 45, the truck will not shift to a higher gear and switch to V4 because it thinks you're loaded down. Enter the calibrator: now when you're doing 45 the speedo says 45, you shift into 6th and V4 and the instantaneous readout goes from 20 to 30mpg. I use this as an example because that's where my truck was running tires 2.5" taller than stock. Now I regularly run in 6th gear at 45mph, rpm just over 1,000, instantaneous 30mpg or more. Now if your tires are less than 2.5" taller than stock, your difference will not be as extreme. It's up to you to decide if it's worth the cost of the Hypertech. For me it was.

[liftkit36]

My 2007 Silverado was doing the same thing, not switching into v4 mode. I live in the mountains and I was getting 17.8mpg when it was working and when it stopped I was getting 15mpg or less. I noticed my truck was in auto 4wd, when I usually run it in 2 high. Also I clicked on the truck info button beside the steering wheel until it said " learn tire position reset'' and I clicked the check button and drove it untill it relearned the tire position. I don't know if it was coincidence or one of the two, but it is working fine now.