AFM disabler and mpg?
- Thread starter Caligirl
- Start date
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Caligirl
Full Access Member
So after deleting AFM and reinstalling ECM, the display stays on V8 but when going downhill or straightaways, it still says 99mpg (like it used to when getting ready to switch to V4). I'm assuming this is because the dash display control doesn't know how to "read" non DOD setup? Anyone else experience that?
My AFM was turned off a while ago in the ECM using a Diablo Predator (essentially flashing the ECM with everything that was there before, but with AFM disabled), I suspect exactly the same way the tuner disabled AFM in your ECM (PCM), just with a different application.
My DIC displays only V8 mode as well, but my instantaneous mileage looks about right for the mode and RPM I am in, that is, going downhill foot off the accelerator I might see 40-50+ MPG, constantly climbing as the time passes with my foot off the gas. When I get to the bottom of the incline and start up the other side foot back on the gas, it might jump back to single digits for a time.
I can't say I have ever seen 99+, whether in AFM mode or after it was disabled, but I only glance at it occasionally when I am interested, many times I don't even have that DIC page up, so maybe 99+ is displayed and I just didn't see it.
avalonandl
Full Access Member
The mpg is relative, has nothing to do with V4. The engines will cut fuel flow when coasting thus 99+ mpg....
Just an update. I took the Yukon out on some errands this morning and watched the DIC most of the time. Even on very steep downhill's, going say 40 mph and foot off the pedal for an extended period of time, I never saw 99+ mpg. I suspect I would have to be traveling on an extended fairly steep downhill at pretty high speeds to see 99+ on the DIC (think some stretches of I80 coming down from Donner).
If you are seeing 99+ mpg on flat stretches, when you are off the gas, maybe he tuned it some, as well as disabling AFM. Just SWAG.
Caligirl
Full Access Member
It was doing the 99+ before deleting. But as AvalonandI already mentioned, it may be just that fuel is cut when coasting. I thought it was odd when I first saw it and thought it was the transition between V4 and V8, but maybe it is just "normal" for my vehicle.
iamdub
Full Access Member
MPG is calculated by engine load, injector duty cycle, vehicle speed and time. I don't have any real hills in my area, at least none long enough to take a decline at highway speeds to get a super high MPG readout on the DIC.
How fast are you going on these downhills? Regardless, your AFM is inactive if the DIC is displaying "V8". Also, your DFCO (Deceleration Fuel Cut Off) may be enabled.
How fast are you going on these downhills? Regardless, your AFM is inactive if the DIC is displaying "V8". Also, your DFCO (Deceleration Fuel Cut Off) may be enabled.
Idriveaho
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That’s normal readings. My equinox with the 4cyl does the same thing.
Caligirl
Full Access Member
50-60 mpg on downhill hwy-oops mph haha
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iamdub
Full Access Member
I assume you meant "mph". 55-60 mph will cover a lot of distance in an hour. Coasting downhill at that speed will consume an extremely small amount of fuel, even when running on eight cylinders. If you were on that same hill, at that same speed for an hour, you'd get 99+ miles per gallon.
