Tale of two AFM systems

[dave1251]

Originally Posted by K20FA5
I'm surprised your Z71 came with 3.08? I though it was part of the package that they came with 3.42?

Mine has the 3.42 and it behaves more like you say your Tahoe does. It's so smooth going between V8 and V4, I don't even notice it much anymore. I just leave it on the digital MPH screen and drive it. I do get better MPG than my wife's 2WD 4Runner though.

Yeah I don't remember any Z71's with the 3.08. My truck is averaging 19.7MPG over it's life.

 

[4WD]

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[dave1251]

Originally Posted by 4WD
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You have a fairly uncommon package but I didn't doubt you. I should have clarified this.

 

[4WD]

Understood, it's an odd selection … I live in a huge truck market but had to drive 135 miles each way to get this truck
(2018 was the last year) …

 

[michaelchristian]

Quote
I do have a 2009 Tahoe calibration file(Gen IV 5.3L/6L80E/3.08:1)......Probably not the exact same as yours, But closer than a LT1 Camaro.

The Max TPS cutoff is 6%.
The Vacuum Delta is even tighter at +/- 0.185 inches of mercury.

Can you please share what program do you use? Because I want to check some of the parameters, but I don't know which program should I use.

 

[4WD]

Did a little test with the Z71 yesterday …
Put it in Tow/Haul mode … would run V4 up to 69 mph (previous was 55 mph)

On same road and direction
T/H mode: 69 mph = 1950 rpm in V4 computer showed 21 mpg
Normal at 69 mph = 1500 rpm in V8 computer showed 23 mpg

 

[Treadstone]

Originally Posted by 4WD
Yeah, I've never had less gear in any truck … without a 6 speed auto and 2 speed transfer case I would of looked for a lower gear … but it actually handles deep sand very well …



It is my understanding that the Z71 package comes with the 3.08 gearing. No options.

 

[wtd]

Back in the day when I bought my 98 Z71 new, the standard rear end gear ratio seemed to be 3.73 which my truck has. Occasionally you would see one with 3.42's. Of coarse my truck only gets about 15 mpg so you are lucky there.

 

[clinebarger]

Originally Posted by 4WD
Did a little test with the Z71 yesterday …
Put it in Tow/Haul mode … would run V4 up to 69 mph (previous was 55 mph)

On same road and direction
T/H mode: 69 mph = 1950 rpm in V4 computer showed 21 mpg
Normal at 69 mph = 1500 rpm in V8 computer showed 23 mpg


I'm guessing T/H mode in V4 was 5th gear?

 

[clinebarger]

Originally Posted by michaelchristian


Can you please share what program do you use? Because I want to check some of the parameters, but I don't know which program should I use.


HP-Tuners, I don't want to clutter 4WD's thread....If you want more info, PM me.

 

[4WD]

Originally Posted by clinebarger
Originally Posted by 4WD
Did a little test with the Z71 yesterday …
Put it in Tow/Haul mode … would run V4 up to 69 mph (previous was 55 mph)

On same road and direction
T/H mode: 69 mph = 1950 rpm in V4 computer showed 21 mpg
Normal at 69 mph = 1500 rpm in V8 computer showed 23 mpg


I'm guessing T/H mode in V4 was 5th gear?


That sounds right …

 

[4WD]

Originally Posted by wtd
Back in the day when I bought my 98 Z71 new, the standard rear end gear ratio seemed to be 3.73 which my truck has. Occasionally you would see one with 3.42's. Of coarse my truck only gets about 15 mpg so you are lucky there.


My 2010 GMC had 4.10 … so it would be at 2200 RPM at my test speed

 

[clinebarger]

Originally Posted by 4WD
Originally Posted by clinebarger
Originally Posted by 4WD
Did a little test with the Z71 yesterday …
Put it in Tow/Haul mode … would run V4 up to 69 mph (previous was 55 mph)

On same road and direction
T/H mode: 69 mph = 1950 rpm in V4 computer showed 21 mpg
Normal at 69 mph = 1500 rpm in V8 computer showed 23 mpg


I'm guessing T/H mode in V4 was 5th gear?


That sounds right …



Increasing RPM reduced load, But at the same time reduced fuel economy......Pumping loss in full display? You would think V4 mode would at the very least mitigate this phenomenon, (Assuming the calculated instant fuel economy display is correct)

Interesting.

 

[4WD]

Yeah … they were pretty quick readings so the mpg is probably the most subjective …

 

[Skippy722]

Originally Posted by clinebarger


Increasing RPM reduced load, But at the same time reduced fuel economy......Pumping loss in full display? You would think V4 mode would at the very least mitigate this phenomenon, (Assuming the calculated instant fuel economy display is correct)

Interesting.


I don't trust the digital mpg readouts. Running average/lifetime one showed 22.9 on this last tank, the trip one showed 23.8, and hand calculated was 24.2.