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Author Topic: active fuel management  (Read 15166 times)
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batmansrobin
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« on: 06/01/08 05:03 PM »

 Help me!
The price of gas was brought up as a topic for dinner conversation and then ideas started to be thrown around Shocked

I have a 2005 Avalanche and I wanted to know if any one has or knows how to allow a 2005 avalanche to have active fuel management like the 2007 and up models. Is it as simple as buying a 2007 or higher computer and harness? And have the computer reprogrammed ? Does anyone have any information on this?

I was just curious being that $95.00 did NOT fill up my gas tank (gas station puts a maximum amount on debit cards) and that E85 is not a possibility in my area. banghead

THANKS
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WILDFIRE
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« Reply #1 on: 06/01/08 08:41 PM »

there'd be a little more then computer work involved, Cosmic Charlie put a link up here that explains some of it
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« Reply #2 on: 06/01/08 09:01 PM »

I actually got better mileage with my 2005 compared to the 2007 I had for a year.  I averaged 17 on the 05 and only got up to around 16.3 on the 2007 when I traded it in.  The mileage promises were one of the reasons I traded up to the 2007 and that was one of the few things that disappointed me.  I like the active fuel management technology and instantaeneous mileage display of the 07+ Avs but I never saw a mileage increase.  Maybe if they had kept the HP the same instead of cracking the 300 barrier.
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« Reply #3 on: 06/02/08 12:27 AM »

Help me!
.......................Is it as simple as buying a 2007 or higher computer and harness? And have the computer reprogrammed ? Does anyone have any information on this?
 banghead


WILDFIRE's link was a good one to explain the "mechanics" and operation of the AFM.  But, to answer your question, you cannot retrofit a 2005 with a AFM.  The heads are entirely different on the 07 & 08 AFMs in that the lifters are captured UNDER the head and not accessible or visable when removing the valley cover.
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« Reply #4 on: 06/04/08 05:28 AM »

I agree Senor Plata.  Although I do not have an 07 or newer av with
the fuel management, I do have a 2005. The reason the 2005 gets
the same if not better mileage than the newer active fuel management
Avvy's, is due to the rear end axle. The ratio.... the only ratio available
in 2005 was a 3.42 rear end on the half ton models. The newer avs offer
the 3:73 and 4:10. So with the active fuel management but lower ratios,
it equals that of a 3:42 rear end in the older models. That's why you will
notice for 2009, chevy or GM in general is going back to a 3:42 rear end
on the avalanche and silverado/sierra trucks to squeeze back the gas
savings combined with the fuel management. I believe gm started experimenting
with gas savings back in 2005 hence the gearing and E85 capability although
running E-85 does not save on gas! You actually burn if faster.
I love my 2005's fuel economy. I average 17.5 miles to the gallon. The 3:42
rear end isnt the best for towing or hauling all of the time but who does that
anyway? Right?
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Rocky07
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« Reply #5 on: 06/04/08 08:50 AM »

I'm not certain I agree with this.  Not saying you get that results, but I think the "engineering" to go to afm with a lower rear gear has produced gains in mpgs from what I have read on this board.

My first AV had a 3.42 rear gear without afm.  I got 13-13.5 mpgs city and 17-18 hwy (the latter on a good day).  My '07 afm gets considerable better than that with the 3.73 rear.

Example:
The '02 running at 70 mph turned 1800 rpms with a 3.42 and got 18 mpg with full time V8
The '07 running at 70 mph turns 2000 rpm with the 3.73 and gets 20.2-21 mpg in V4 mode.  Even in V8 mode, it runs steady at 18 mpgs

Therefore, regardless of the rear gear and resulting higher rpms, shifting to V4 is a real gas saver.

That has been my experience running my '02 to 161K miles and the '07 just turning 40K
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« Reply #6 on: 06/04/08 09:37 AM »

Rocky, i think everyone's individual results vary.  My statement was based on
threads and posts I have read here by members who have the newer av's with
AFM.  I am not an engineer by any means but one would think that no matter
how many cylinders are activated,,,, running higher rpms would draw more fuel.
My 05 with 3:42 will easily run down the highway reading minimum 19 and as high
as 21 mpg, of course with no head wind.  Tire pressure has alot to do with this also.
There are so many factors involved in gas mileage. I really think GM is still in the
experimental stages of gaining most efficient economy in their large suv's and trucks.
I was basically trying to state that although my 05 does not have AFM, it gets the
same if not better mileage than the newear av's that due... because of the rear
end.  Personally, I do not count city mileage? How can we? Some of us floor it off the
line at stop lights while others dont.  Again , way too many factors.  But i see what
you are saying. There were many changes from 02 to 05 with the vortec engines for
better fuel economy.
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« Reply #7 on: 06/04/08 11:19 AM »

05SilverAvMan....oh, I don't doubt your experiences at all.  And there has no doubt been some refinement of the 5.3L non-afm from '02 to your '05.  I have seen others post much lower mpgs that I get even with the afm which totally puzzles me.  But, I have said and I know your agree your right foot and style of driving has the single greatest impact on your mpgs.

Incidentally, I checked my latest mpgs this morning on two full tanks of city only driving.  The average has been 15.4 mpgs.  That down a bit from a normal 15.8-16.2 but the weather has been very hot here and the a/c is working its heart out.  My '02 never broke the 13.5 barrier in city driving in its 161K miles.
« Last Edit: 06/05/08 08:02 AM by Rocky07 » Logged

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« Reply #8 on: 06/04/08 04:16 PM »

I have an 05 and am getting about the same MPGs as the newer AV's with the AFM. But as 05SilverAvMan said this is with 3:42 rear end  Thumbs down.  I wish the 05 had the 3:73 rear.
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« Reply #9 on: 06/04/08 04:50 PM »

The 3:42 is going into the 09s due to the tranny change. The 6-spd has significantly lower low gear ratios and just about the same OD.

Undergearing something this heavy can get counter productive; especially with AFM. I think the 3:73s with the 4L60e seem to be a pretty well balanced setup. I insisted on 4:10s because I live at 6000ft. I'm way past my boy racer stage, but at this altitude the 3:73s still feel sluggish to me and spend too much time hunting between gears, just trying to maintain, at freeway speed on rolling terrain. That's an annoying problem I had with my old Silverado with the same drivetrain; and 3:73s
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« Reply #10 on: 06/05/08 08:09 AM »

As soon as the '09 6 speed comes out, that's when I'll trade in the '07......maybe.  The price tag on these things are getting ridiculous even with the GM discounts that I've got on the last 2 AVs.
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« Reply #11 on: 06/05/08 02:36 PM »

I have a 07 with 3:73 gears. lots of highway miles averaging 18-19 mpg.
anyone have a great idea of how to improve mileage other than slowing down?
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« Reply #12 on: 06/05/08 02:40 PM »

Wished I has some wisdom to share.  How many miles on it?  Lousiana isn't that hilly so you shouldn't have grades as an issue.  Have you cleaned your MAF?  How's your tire presure?  Is is a Z71?
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« Reply #13 on: 06/06/08 05:56 PM »

I have a 07 with 3:73 gears. lots of highway miles averaging 18-19 mpg.
anyone have a great idea of how to improve mileage other than slowing down?

Assuming it's a 4x4 and you don't have a 90th percentile light right foot, what's wrong with 18 - 19 mpg? But to answer your question, you could try a custom tuner.
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« Reply #14 on: 06/09/08 05:45 PM »

not 4x4 / travel in 7 states so we see some grades. 18-19 not bad, but a $4.00 /gal would like options to improve.
thanks
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« Reply #15 on: 06/10/08 12:31 PM »

18-19 is pretty good considering the heat & humidity in the SE (assuming you're running A/C)
I myself, have noticed better economy turning off the AFM feature. The instant economy readout is really great - I've checked it both with afm engaged and without, and the mpg's go just as high when under light load, and, obviously, no lower under heavy load. MN's terrain fairly level, but it's hilly enough that each trip is up-hill one way, and down-hill the next, so I always seem to gain mpg going one way, and lose it the other.
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« Reply #16 on: 06/15/08 12:58 PM »

I have an 08 with 4.10's, 6.0, 2wd and at 65 mph, I average 17mpg. At 65, its turning at 2K.
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« Reply #17 on: 06/17/08 06:59 AM »

One other factor not mentioned is the gasoline itself... the amount of additives and ethanol content vary and that does affect your gas mileage somewhat. So far my 3 week old '08 Z71 seems pretty close to what my '05 Z71 (21mpg on a good trip several times) did so I hope it will improve as it breaks in.
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« Reply #18 on: 06/17/08 09:22 PM »

18-19 is pretty good considering the heat & humidity in the SE (assuming you're running A/C)
I myself, have noticed better economy turning off the AFM feature. The instant economy readout is really great - I've checked it both with afm engaged and without, and the mpg's go just as high when under light load, and, obviously, no lower under heavy load. MN's terrain fairly level, but it's hilly enough that each trip is up-hill one way, and down-hill the next, so I always seem to gain mpg going one way, and lose it the other.

Agreed, look at soem of the less capable trucks AND cars out there that can't touch 18-19 MPGs..it's just thta we have the 31 gallon tank so to fill it is a swift kick in the wallet.

Question - how do you turn of the AFM feature??
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« Reply #19 on: 06/18/08 02:07 PM »

"Question - how do you turn of the AFM feature??"
You have to have a tuner. I use a Diablosport Predator. It's a handheld, and not as powerful (or complex) as HPTuners or EFILive, but it allows me to make enough changes to the pcm to put an extra 35 HP and 30+ ft/lbs of torque to the wheel, while upping my avg mpg to around 18-20 in the warm months, and 16-18 in the cold. at $400, it paid for itself in less than 1 year, not to mention making the av more fun to drive  Drive!
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« Reply #20 on: 06/18/08 02:24 PM »

"Question - how do you turn of the AFM feature??"
You have to have a tuner. I use a Diablosport Predator. It's a handheld, and not as powerful (or complex) as HPTuners or EFILive, but it allows me to make enough changes to the pcm to put an extra 35 HP and 30+ ft/lbs of torque to the wheel, while upping my avg mpg to around 18-20 in the warm months, and 16-18 in the cold. at $400, it paid for itself in less than 1 year, not to mention making the av more fun to drive  Drive!

Do I understand that you get better mpgs with the AFM deactivated?
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« Reply #21 on: 06/19/08 01:54 PM »

Yeah, believe it or not   Shocked
It's not huge, but all things being equal (same drive every day, same temps + or - 10 degrees, same speed), I've gained mpg since turning it off. I'd say around .7. The reason I tried it initially was to monitor the sound of my dual exhaust, as people complained that it sounded like a rice burner when V4 kicked in. To my surprise, I noticed that when coasting, it still read 99MPG, and when under light load on the highway, it still climbs over 50MPG, while the low end remains unchanged, since AFM can't engage while rpm's are climbing. It actually seems smoother to me, since I could feel a lurch occasionally when AFM engaged/disengaged.
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« Reply #22 on: 06/24/08 02:36 PM »

I was perfectly happy with AFM until I got my truck tuned. Not exactly unhappy with it now, but it's often more noticeable when it disengages, particularly when using cruise control. That's possibly because of the change in how it picks up the throttle; more responsive now. I'm about to take off on a 3500 - 4000 mile trip in a week or two. I'll decide if I want to keep the AFM feature when I get back
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« Reply #23 on: 06/26/08 10:45 PM »

Alright, for you pre-2007 'Lanchers who want AFM. I think I came up with a solution -

OK, I was talking about it with my friends at the bar tonight and we mapped it out after putting our combined years of auto experience together. The funny thing is the key to getting it to work after looking under the hoods of a couple Avs for configuration and set up is that you need to not be using the second battery tray. So lets assume, you are not and now you are ready for the AFM mod.

First you need to run a wiring from a switch mounted in the dash to your battery, those wires will wind up attached to 4 small LEDs. This is critical - you need enough length between the LEDs to allow for placement. Now locate the four cylinders that are to be deactivated _ we weren't sure which - I mean we were at a bar after all and could not have access to all the tech docs - OK, mount each LED either on the corresponding spark plug wire for the cylinder that will be deactivated or near it. Now, were your spare/second battery tray is - you need to place some thin foam or something like that to protect that area from the elements. Lastly, you need to get yourself a midget - excuse me a short person or your delinquent child if you have one and explain to them that they are going to participate in an exercise to help the countries dependance on foreign oil and help the environment all at once. You then walk them over to your  'Lanche pick em up and sit em on the foamed spare battery tray. Explain to them everytime they see the LEDs go on they are to pull the sparkplug wires of the plugs. When the light goes off, they reattach them. Throw 'em a couple bottles of water, shut the hood and let her rip. Feed 'em every now and again and you'll get many miles out of this mod.

There you go - any other issues you want to resolve???
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« Reply #24 on: 06/27/08 08:53 AM »

I beleive it will work.....


 Big laughter with tears Big laughter with tears Big laughter with tears Big laughter with tears
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