2007 Tahoe DOD

ok, so the displacement on demand feature of the new tahoe is suppose to improve gas milage but i've yet to witness any real effect.
situation 1: cruising at 75mph down I-20 the engine only drops to V4 when there is
no load on the motor (going down a slight grade). the way it was originally explained to me was that if you were cruising at a constant speed the motor would drop to V4 and stay that way until a significant demand was placed on the engine. question: was this explained wrong or do i have a bad computer?
situation 2: one would think that at idle or in stop and go traffic <20 mph the motor would also default to V4 mode. however, that is not the case. anytime the vehicle speed is less than 20 mph (maybe 25) the engine is always in V8 mode. that just doesn't make sense to me given that is a time when there is very little demand on the motor. question: again, is this a computer problem or is there some other reason to justify?
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On 26 Jun 2006 12:23:33 -0700, snipped-for-privacy@gmail.com wrote:

The misconception here is that it takes a good bit of power to cruise at 75 MPH so it is not likely to drop to cyls much doing that. Try 60 or 65 MPH because it still takes the same power to get down the road and it has to come from somewhere

IT low speed in 4 cyl mode it would be very low on power and straining more to overcome internal losses and run accesories and throttle responce would be poor too and this is why transition take place only at higher RPM's. Many years ago IH had a 466 v8 diesel that ran on 4 cyl below 1000 RPM on the theory that it would save fuel idling but it was soon dropped because responce below 1000 RPM was bad and it was nasty to start in really cold weather becuase they extra cylinder were disabled regardless of tempature. ----------------- The SnoMan www.thesnoman.com
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well who on god's green earth cruises down the interstate at 60mph? that's a recipe for a good rear ending. moreover, even in the city on long stretches of road, the engine won't drop to V4 even at 40mph unless your going down a hill or have your foot off the throttle.
i'm not trying to dispute your analysis but why tout DOD as a fuel saver when it is only active 2% of the time. i'm sure chevy can "prove" it on a dyno and/or in a strictly controlled environment but "real world" performance is terrible.
SnoMan wrote:

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wrote:

You cruise at 75 here and you will get a ticket big time and quickly in certain areas. They start busting you around 70. That aside as speed increase so does drag and fuel consumption. 65 or a bit more is a good compromise here. (some cars are a lot more aerodynamic and pay less penalty for speed than SUV's) And besdies if you do get rear ended, it is not your fault and the poor sap that did it can foot the bill and I would never speed just to not be rear ended. When they run EPA test cycle they never exceed 59 MPH in hiway test cycel and average 48 MPH so the fault is in the test which is badly skewed to favor Detriot and to give consumers a false impresion of what to really expect. If the EPA would crack down and redo tests then the consumer would know more what they are really going to get but attempts to change it have been blocked by current admin because it would not be freindly to Detriot or Big Oil profits. At the link below you will find some info on test prceedures and on to a Consumers Union that tests several models in real world usage and the differences is plain to see and a lot closer to what to expect.
http://forum.snoman.com/viewtopic.php?t 3 ----------------- The SnoMan www.thesnoman.com
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haha, i cruised 70-75 to get a feel for the gas milage i was getting. i generally run 85-90 down the interstate. yes, i have a few tickets but most state patrol down here run with their radar guns on all the time so my detector gives me fair warning to slow down.
in the words of van halen "i can't drive, 55!"
SnoMan wrote:

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wrote:

WHo said 55? Here radar detectors will not save you because the state boys hunt in packs here and use laser and aircraft using old VasCar (timing you between two spots from air) I have travel a lot of states and they can be wicked here in spots. They only use radar when hunting alone and even then not that much to give their position away. ----------------- The SnoMan www.thesnoman.com
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Here in Texas most hiways are 70 mph, so yes the cops usually won't touch you unless your doing close to or over 80. By the way it was Sammy Hagar that sang "I can't drive 55!", and that was when he was on his own before he replaced David Lee Roth in Van Halen.
Keith
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you beat me to the punch keith.
i couldn't remember if it was hagar or van hagar or van halen so i went with the original (best).....van halen.
Keith wrote:

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snoman,
i just realized you said they start busting you around 70......what's the friggin' speed limit up there? i'm from texas and most every highway in the state (interstate and state) the speed limit is at least 65 but most often 70. they don't really mess with you until you go over 75.
SnoMan wrote:

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wrote:

Ohio, the State boys bust you at 71 when they are on the prowl and they can be really nasty on some strips. I have seen them pull over several cars at once too and have several officers right tickets as more are waved over to them. Yo drive 75 around them you will get busted and the whole pack too if your in one if there is more than one of them to do it.
----------------- The SnoMan www.thesnoman.com
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Duuuude, that was Sammy Hagar

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