Active Fuel Management

[Domano 68]

It looks like the new 07 Silverado's have the active fuel managment system that shuts down 4 cyls on light demand, similar to the 06 Tahoes. How much fuel savings does this produce over the standard engine? Thanks!

[HawkeyeOC]

It looks like the new 07 Silverado's have the active fuel managment system that shuts down 4 cyls on light demand, similar to the 06 Tahoes.  How much fuel savings does this produce over the standard engine?  Thanks!

 

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The local GMC dealer I talked to claims their customers are seeing a 1 to 2 mpg improvement on the Yukons. Take it for what it's worth.

 

When I test drove one, it would only go into 4cyl mode when coasting to a stop. I am sure what you get in reality depends a lot on driving habits. Don't expect a huge improvement over the standard engine.

[Suf Daddy]

On the first 1,000 miles on our 5.3L DOD gizmo the v4 to v8 appears seamless.

 

So far the V8 mode switches to V4 above 22/4 MPG. The jump gains 4 MPG on avg.

 

I see HIGH 20's (28-ish) and low 30's OFTEN, but the start and stops KILL your avg with 5 & 9 MPG readings even just BARELY cracking the throttle to MAXIMIZE MPG....

 

This is one truck that benefits from lifting JUSt before the hill peak/crest and cracking the throttle on the downhill to accelerate with the V4 mode on.

Any decent pedal pressure kicks in the V8.

 

So far the truck (2007 Yukon SLT 3.83 gears AFAIK) with hills (Sea Level to 1500 feet; Berkshires), interstate (I-90), lots of flats NY finger lakes 414) and small trailer (snowmobile like) (MA - Cape Cod / Rt3) both empty and full of 6 people with a full tank of gas............ 17.8 MPG with a REALLY LIGHT foot. Avg Ambinet temp 70 degrees, mostly light rain.

 

This is UP from the Mrs., putting on the second 200 miles with a Starting avg of 15.4 or so....

The dealer ran the first 150 miles ferrying the truck so who knows if it was on cruise or flogged............ this is 5 +/- the PSL for a change...............

 

The V-8 to V-4 gains look awesome around 40 MPH and seem decent around 70-72 MPH on the flat interstate........

There does seem to be a quagmire of 50 - 65 MPH were the truck seems to lack the power to propell along unless the V-4 kicks into V-8.......

 

I suspect (without even looking) that the torque curve must start around 1500 rpm where the motor settles in around 2,000 RPM at 72 MPH.......... Speeds in the 50 - 60 MPH range are 1500 or below.

 

I DO notice that if you LIGHT foot it (no cruise) on the flat interstate, the V-4 mode slowly looses MPH so that after a while the V-8 mode kicks in to prop up the speed. On cruise the system seems perfect. VERY hard to find fault.

 

The V4 mode DOES hold its own at 72 MPH on LEVEL interstate, so you midwestern and FLA drivers should squeeze some nice gains from the Displacement on Demand system.

 

The DOD was the SOLE reason we when with this Yukon set up. Styling was a STRONG second.

 

-Suf Daddy Revised...........

[Frozen001]

Good reply Suf daddy...

 

Just out of curiosity the number you gave for MPG are those hand calculations or what the DIC reads??

[Dr. DanH]

On the first 1,000 miles on our 5.3L DOD gizmo the v4 to v8 appears seamless.

 

So far the V8 mode switches to V4 above 22/4 MPG.  The jump gains 4 MPG on avg.

 

I see HIGH 20's (28-ish) and low 30's OFTEN, but the start and stops KILL your avg with 5 & 9 MPG readings even just BARELY cracking the throttle to MAXIMIZE MPG....

 

This is one truck that benefits from lifting JUSt before the hill peak/crest and cracking the throttle on the downhill to accelerate with the V4 mode on. 

Any decent pedal pressure kicks in the V8.

 

So far the truck (2007 Yukon SLT 3.83 gears AFAIK) with hills (Sea Level to 1500 feet; Berkshires), interstate (I-90), lots of flats NY finger lakes 414) and small trailer (snowmobile like) (MA - Cape Cod / Rt3) both empty and full of 6 people with a full tank of gas............ 17.8 MPG with a REALLY LIGHT foot.  Avg Ambinet temp 70 degrees, mostly light rain.

 

This is UP from the Mrs., putting on the second 200 miles with a Starting avg of 15.4 or so....

The dealer ran the first 150 miles ferrying the truck so who knows if it was on cruise or flogged............  this is 5 +/- the PSL for a change...............

 

The V-8 to V-4 gains look awesome around 40 MPH and seem decent around 70-72 MPH on the flat interstate........

There does seem to be a quagmire of 50 - 65 MPH were the truck seems to lack the power to propell along unless the V-4 kicks into V-8.......

 

I suspect (without even looking) that the torque curve must start around 1500 rpm  where the motor settles in around 2,000 RPM at 72 MPH..........  Speeds in the 50 - 60 MPH range are 1500 or below.

 

I DO notice that if you LIGHT foot it (no cruise) on the flat interstate, the V-4 mode slowly looses MPH so that after a while the V-8 mode kicks in to prop up the speed.  On cruise the system seems perfect.  VERY hard to find fault.

 

The V4 mode DOES hold its own at 72 MPH on LEVEL interstate, so you midwestern and FLA drivers should squeeze some nice gains from the Displacement on Demand system.

 

The DOD was the SOLE reason we when with this Yukon set up.  Styling was a STRONG second.

 

-Suf Daddy  Revised...........

 

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SDad,

How can you tell if/when it does its 8 to 4 thing. Mine is supposed to have it and there is some light on the insrtument panel, but on start up, when all IP idiot lights are lit...no 4/8 indicator. Did the salesman BS me?

 

Dan

[HD03]

Dr. DanH you can see it in the DIC

[Dr. DanH]

I checked the VIN...it's got a 'K'. The standard 6.0l. No active fuel mgt. I had looked at quite a few 'burbs, guess I got a them confused.

[mottati]

so does anyone know how this feature works? In the early 80's, cadillac had their infamous V8-6-4 engine, which had solenoids on the valves, and would disable cylinders by closing off valves on 2 or 4 cylinders. The pistons would still go up and down, essentially compressing and expanding gasses, but no fuel going thru since all the valves closed.

 

How does this system work? Just shut down fuel injectors?

curious.

Mike

[Dr. DanH]

so does anyone know how this feature works? In the early 80's, cadillac had their infamous V8-6-4 engine, which had solenoids on the valves, and would disable cylinders by closing off valves on 2 or 4 cylinders. The pistons would still go up and down, essentially compressing and expanding gasses, but no fuel going thru since all the valves closed.

 

How does this system work? Just shut down fuel injectors?

curious.

Mike

 

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As I understand it directly from GM's engine Guru, Sam Somethingorother the 8-6-4 thing was a nightmare. The 8-4 is much better. Fuel supply shuts down in 4 of the cylinders AND (get this) the cylinders that do shut down change each time to aviod uneven wear patterns. Pretty Cool,huh?

[ZZ327]

actually all the cylinders move all the time like normal. they only shut off fuel / and close the valves I think. with special spring loaded lifters

 

http://www.gm.com/company/gmability/adv_te...dod_050803.html

[mottati]

As I understand it directly from GM's engine Guru, Sam Somethingorother the 8-6-4 thing was a nightmare.  The 8-4 is much better.  Fuel supply shuts down in 4 of the cylinders AND (get this) the cylinders that do shut down change each time to aviod uneven wear patterns.  Pretty Cool,huh?

 

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that is pretty cool how it alternates cylinders.

 

As for the v8-6-4, my parents had a cadillac with that engine ,1981 eldorado (get this, they traded in a 79 seville diesel on it, around 84 or so). I remember the magazines at the time telling about how bad/unreliable it was, but they never had any issues with it, until it was wrecked in the early 90's with 130K + on the clock. Then again, they got 190K out of their previous diesel cadillac, so they must have just had good gm engine karma at the time.

Thanks,

Mike

[mottati]

actually  all the cylinders move all the time like normal.  they only shut off fuel /  and close the valves I think. with special spring loaded lifters

 

http://www.gm.com/company/gmability/adv_te...dod_050803.html

 

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thanks for that link. I figured the pistons still did their thing, wasn't sure if the valves still opened and closed. They don't, so no pumping losses, only frictional losses. I wish they gave more detail on how they de activate the valves, via the lifters or the rockers, but a little info is better than none, imho.

Thanks,

Mike

[mdub]

so does anyone know how this feature works? In the early 80's, cadillac had their infamous V8-6-4 engine, which had solenoids on the valves, and would disable cylinders by closing off valves on 2 or 4 cylinders. The pistons would still go up and down, essentially compressing and expanding gasses, but no fuel going thru since all the valves closed.

 

How does this system work? Just shut down fuel injectors?

curious.

Mike

 

<{POST_SNAPBACK}>

 

 

 

As I understand it directly from GM's engine Guru, Sam Somethingorother the 8-6-4 thing was a nightmare. The 8-4 is much better. Fuel supply shuts down in 4 of the cylinders AND (get this) the cylinders that do shut down change each time to aviod uneven wear patterns. Pretty Cool,huh?

 

<{POST_SNAPBACK}>

 

 

 

I'm interested to learn where this information came from about alternating which cylinders shut down to avoid uneven wear. I've never seen that stated anywhere in technical documentation on either GM's or Chrysler's DOD system. This is a concern, and it seems like the manufacturers brag more about it if they had really solved the problem.

 

Can you privide a link/reference to this information?

 

Thanks

[Mark_in_Tulsa]

so does anyone know how this feature works? In the early 80's, cadillac had their infamous V8-6-4 engine, which had solenoids on the valves, and would disable cylinders by closing off valves on 2 or 4 cylinders. The pistons would still go up and down, essentially compressing and expanding gasses, but no fuel going thru since all the valves closed.

 

How does this system work? Just shut down fuel injectors?

curious.

Mike

 

<{POST_SNAPBACK}>

 

 

 

As I understand it directly from GM's engine Guru, Sam Somethingorother the 8-6-4 thing was a nightmare. The 8-4 is much better. Fuel supply shuts down in 4 of the cylinders AND (get this) the cylinders that do shut down change each time to aviod uneven wear patterns. Pretty Cool,huh?

 

<{POST_SNAPBACK}>

 

 

 

I'm interested to learn where this information came from about alternating which cylinders shut down to avoid uneven wear. I've never seen that stated anywhere in technical documentation on either GM's or Chrysler's DOD system. This is a concern, and it seems like the manufacturers brag more about it if they had really solved the problem.

 

Can you privide a link/reference to this information?

 

Thanks

 

<{POST_SNAPBACK}>

 

 

 

Every bit of info I have read, says that is deactivates the same cylinders (1, 4, 6 and 7). every time.

[ZZ327]

so does anyone know how this feature works? In the early 80's, cadillac had their infamous V8-6-4 engine, which had solenoids on the valves, and would disable cylinders by closing off valves on 2 or 4 cylinders. The pistons would still go up and down, essentially compressing and expanding gasses, but no fuel going thru since all the valves closed.

 

How does this system work? Just shut down fuel injectors?

curious.

Mike

 

<{POST_SNAPBACK}>

 

 

 

As I understand it directly from GM's engine Guru, Sam Somethingorother the 8-6-4 thing was a nightmare. The 8-4 is much better. Fuel supply shuts down in 4 of the cylinders AND (get this) the cylinders that do shut down change each time to aviod uneven wear patterns. Pretty Cool,huh?

 

<{POST_SNAPBACK}>

 

 

 

I'm interested to learn where this information came from about alternating which cylinders shut down to avoid uneven wear. I've never seen that stated anywhere in technical documentation on either GM's or Chrysler's DOD system. This is a concern, and it seems like the manufacturers brag more about it if they had really solved the problem.

 

Can you privide a link/reference to this information?

 

Thanks

 

<{POST_SNAPBACK}>

 

 

 

 

Read post # 10 There is no way they can alternate which pistons run. there is only 1 crankshaft